# Why does attr\_accessor create a property, but method is just a 	method?

**URL:** <https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979>\
**Category:** IronRuby\
**Created:** [July 21, 2010, 7:00pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979 "2010-07-21T19:00:13Z")\
**Posts on this page:** 19\
**Page:** 1

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 21, 2010, 7:00pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/1 "2010-07-21T19:00:13Z")

</div>

This is a cross-post from Stack Overflow, but I haven’t heard a peep  
there,  
so I figured I’d try here:

I am playing around with the interop between C# and IronRuby. I have  
noticed that if I define a property in Ruby using `attr_accessor`, it is  
presented to C# as a property. If, on the other hand, I create the  
exact  
same code manually, it comes back as a method.

For example, take this code:

```
var engine = IronRuby.Ruby.CreateEngine();
string script = @"
  class Test
    attr_accessor :automatic

    def manual
      @manual
    end

    def manual=(val)
      @manual = val
    end

    def initialize
      @automatic = ""testing""
      @manual = ""testing""
    end
  end

  Test.new
";
var testObject = engine.Execute(script);

var automatic = testObject.automatic;
var manual = testObject.manual;

```

When you look at the C# `automatic` variable, the value is a string of  
“testing”. If you look at the C# `manual` variable, it is type  
IronRuby.Builtins.RubyMethod.

Ultimately, I want to create my own properties in Ruby that can be used  
in  
C#, but I can’t seem to make them be visible as properties like  
`attr_accessor` does.

I THINK, that there is some magic going on in the Module code of the  
Ruby  
source code (ModuleOps.cs:DefineAccessor). Is there any way to do this  
in  
Ruby code directly?

Thanks,  
Brian

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 22, 2010, 3:04pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/2 "2010-07-22T15:04:32Z")

</div>

So, I haven’t heard anything about this yet on Stack Overflow, or this  
list.

Does anyone know if this is this a bug in IronRuby interop?

Thanks,  
Brian

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 22, 2010, 3:26pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/3 "2010-07-22T15:26:11Z")

</div>

I believe this works as designed.

The problem is that Ruby doesn’t otherwise distinguish syntactically  
between a property and a method with no parameters. Imagine that you’re  
in tooling such as Visual Studio. By default, the values of properties  
are automatically displayed in the debugger and in tool tips. But if I  
happen to have a no-args method named format\_cdrive, I probably don’t  
want that code to be run just to inspect its value. Effectively,  
attr\_accessor, attr\_reader and attr\_writer are used by IronRuby as  
signals that indicate this operation is free of potentially-nasty side  
effects.

From: removed\_email\_address@domain.invalid  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] On Behalf Of Brian G.  
Sent: Thursday, July 22, 2010 5:49 AM  
To: removed\_email\_address@domain.invalid  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

So, I haven’t heard anything about this yet on Stack Overflow, or this  
list.

Does anyone know if this is this a bug in IronRuby interop?  
Thanks,  
Brian

On Wed, Jul 21, 2010 at 12:34 PM, Brian G.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
This is a cross-post from Stack Overflow, but I haven’t heard a peep  
there, so I figured I’d try here:

I am playing around with the interop between C# and IronRuby. I have  
noticed that if I define a property in Ruby using `attr_accessor`, it is  
presented to C# as a property. If, on the other hand, I create the  
exact same code manually, it comes back as a method.

For example, take this code:

```
var engine = IronRuby.Ruby.CreateEngine();
string script = @"
  class Test
    attr_accessor :automatic

    def manual
      @manual
    end

    def manual=(val)
      @manual = val
    end

    def initialize
      @automatic = ""testing""
      @manual = ""testing""
    end
  end

  Test.new
";
var testObject = engine.Execute(script);

var automatic = testObject.automatic;
var manual = testObject.manual;

```

When you look at the C# `automatic` variable, the value is a string of  
“testing”. If you look at the C# `manual` variable, it is type  
IronRuby.Builtins.RubyMethod.

Ultimately, I want to create my own properties in Ruby that can be used  
in C#, but I can’t seem to make them be visible as properties like  
`attr_accessor` does.

I THINK, that there is some magic going on in the Module code of the  
Ruby source code (ModuleOps.cs:DefineAccessor). Is there any way to do  
this in Ruby code directly?

Thanks,  
Brian

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 22, 2010, 4:06pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/4 "2010-07-22T16:06:01Z")

</div>

Curt,

Thank you very much for engaging 🙂

Although I understand what you are saying, from an interop perspective,  
this  
is not desirable.

In fact, the WPF binding system will see two methods (foo and foo=(val))  
and  
determine that they are properties that can be bound to. C#, on the  
other  
hand, can’t use them as properties. Furthermore, if I want a simple  
side  
effect (like property change notification) in a property, it makes sense  
for  
me to define my own foo and foo=(val) methods. Again, WPF can get these  
notifications and read the “properties”, but C# just sees methods.  
Another  
case might be where properties are just wrappers around hashes… a case  
I  
am running into.

At a very minimum, I would expect to be able to create get\_foo and  
set\_foo(value) in ruby to have them be seen as .Net properties, but this  
doesn’t seem to work either.

In general, I am trying to understand good interop practices between my  
ruby  
and C# and WPF code, but I can’t seem to make anything other than  
attr\_accessor work.

Brian

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 22, 2010, 4:10pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/5 "2010-07-22T16:10:42Z")

</div>

Thinking on this further, if there were some sort of interop-specific  
class  
method… like attr\_clr\_property :foo, that caused any methods named foo  
and  
foo=(var) to be visible to .Net as properties, that would be sufficient.

Any thoughts on this?  
B

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 22, 2010, 4:14pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/6 "2010-07-22T16:14:48Z")

</div>

WPF binds by effectively treating the Ruby object as “dynamic” - that  
is, it goes through IDynamicMetaObjectProvider. You can get the same  
behavior from C# by saying

dynamic obj = SomeRubyObject();  
dynamic foo = obj.foo;

Is this not sufficient for your needs?

From: removed\_email\_address@domain.invalid  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] On Behalf Of Brian G.  
Sent: Thursday, July 22, 2010 6:55 AM  
To: removed\_email\_address@domain.invalid  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

Thinking on this further, if there were some sort of interop-specific  
class method… like attr\_clr\_property :foo, that caused any methods  
named foo and foo=(var) to be visible to .Net as properties, that would  
be sufficient.

Any thoughts on this?  
B  
On Thu, Jul 22, 2010 at 9:34 AM, Brian G.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
Curt,

Thank you very much for engaging 🙂

Although I understand what you are saying, from an interop perspective,  
this is not desirable.

In fact, the WPF binding system will see two methods (foo and foo=(val))  
and determine that they are properties that can be bound to. C#, on the  
other hand, can’t use them as properties. Furthermore, if I want a  
simple side effect (like property change notification) in a property, it  
makes sense for me to define my own foo and foo=(val) methods. Again,  
WPF can get these notifications and read the “properties”, but C# just  
sees methods. Another case might be where properties are just wrappers  
around hashes… a case I am running into.

At a very minimum, I would expect to be able to create get\_foo and  
set\_foo(value) in ruby to have them be seen as .Net properties, but this  
doesn’t seem to work either.

In general, I am trying to understand good interop practices between my  
ruby and C# and WPF code, but I can’t seem to make anything other than  
attr\_accessor work.

Brian  
On Thu, Jul 22, 2010 at 9:17 AM, Curt H.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
I believe this works as designed.

The problem is that Ruby doesn’t otherwise distinguish syntactically  
between a property and a method with no parameters. Imagine that you’re  
in tooling such as Visual Studio. By default, the values of properties  
are automatically displayed in the debugger and in tool tips. But if I  
happen to have a no-args method named format\_cdrive, I probably don’t  
want that code to be run just to inspect its value. Effectively,  
attr\_accessor, attr\_reader and attr\_writer are used by IronRuby as  
signals that indicate this operation is free of potentially-nasty side  
effects.

From:  
removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]  
On Behalf Of Brian G.  
Sent: Thursday, July 22, 2010 5:49 AM  
To: removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

So, I haven’t heard anything about this yet on Stack Overflow, or this  
list.

Does anyone know if this is this a bug in IronRuby interop?  
Thanks,  
Brian

On Wed, Jul 21, 2010 at 12:34 PM, Brian G.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
This is a cross-post from Stack Overflow, but I haven’t heard a peep  
there, so I figured I’d try here:

I am playing around with the interop between C# and IronRuby. I have  
noticed that if I define a property in Ruby using `attr_accessor`, it is  
presented to C# as a property. If, on the other hand, I create the  
exact same code manually, it comes back as a method.

For example, take this code:

```
var engine = IronRuby.Ruby.CreateEngine();
string script = @"
  class Test
    attr_accessor :automatic

    def manual
      @manual
    end

    def manual=(val)
      @manual = val
    end

    def initialize
      @automatic = ""testing""
      @manual = ""testing""
    end
  end

  Test.new
";
var testObject = engine.Execute(script);

var automatic = testObject.automatic;
var manual = testObject.manual;

```

When you look at the C# `automatic` variable, the value is a string of  
“testing”. If you look at the C# `manual` variable, it is type  
IronRuby.Builtins.RubyMethod.

Ultimately, I want to create my own properties in Ruby that can be used  
in C#, but I can’t seem to make them be visible as properties like  
`attr_accessor` does.

I THINK, that there is some magic going on in the Module code of the  
Ruby source code (ModuleOps.cs:DefineAccessor). Is there any way to do  
this in Ruby code directly?

Thanks,  
Brian

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 22, 2010, 4:14pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/7 "2010-07-22T16:14:48Z")

</div>

No, that is not sufficient, because it does not work. Assuming the  
example  
I posted, this code fails:

dynamic automatic = testObject.automatic;  
dynamic manual = testObject.manual;

dynamic autoLength = automatic.Length;  
dynamic manualLength = manual.Length; // RuntimeBinderException

`manual.Length` fails because `manual` is of type  
`IronRuby.Builtins.RubyMethod` and `Length` is not defined.

This is my problem… since ‘manual’ is not exposed to .Net as a  
property,  
it fails.

Brian

P.S. I REALLY appreciate you talking through this with me.

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 22, 2010, 5:32pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/8 "2010-07-22T17:32:40Z")

</div>

I don’t know that you should appreciate anything I say; I haven’t worked  
on IronRuby in over a year. 😃

A long time ago, I wrote code for ICustomTypeDescriptor that does  
property inference based on the presence of arity-0 “foo” and arity-1  
“foo=” but I had assumed that WPF was now binding via IDMOP and not  
ICustomTypeDescriptor. Since this doesn’t work via “dynamic”, I guess  
that’s not the case. Maybe Tomáš has something to add?

From: removed\_email\_address@domain.invalid  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] On Behalf Of Brian G.  
Sent: Thursday, July 22, 2010 7:10 AM  
To: removed\_email\_address@domain.invalid  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

No, that is not sufficient, because it does not work. Assuming the  
example I posted, this code fails:

dynamic automatic = testObject.automatic;  
dynamic manual = testObject.manual;

dynamic autoLength = automatic.Length;  
dynamic manualLength = manual.Length; // RuntimeBinderException

`manual.Length` fails because `manual` is of type  
`IronRuby.Builtins.RubyMethod` and `Length` is not defined.

This is my problem… since ‘manual’ is not exposed to .Net as a  
property, it fails.

Brian

P.S. I REALLY appreciate you talking through this with me.

On Thu, Jul 22, 2010 at 10:01 AM, Curt H.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
WPF binds by effectively treating the Ruby object as “dynamic” - that  
is, it goes through IDynamicMetaObjectProvider. You can get the same  
behavior from C# by saying

dynamic obj = SomeRubyObject();  
dynamic foo = obj.foo;

Is this not sufficient for your needs?

From:  
removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]  
On Behalf Of Brian G.  
Sent: Thursday, July 22, 2010 6:55 AM

To: removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

Thinking on this further, if there were some sort of interop-specific  
class method… like attr\_clr\_property :foo, that caused any methods  
named foo and foo=(var) to be visible to .Net as properties, that would  
be sufficient.

Any thoughts on this?  
B  
On Thu, Jul 22, 2010 at 9:34 AM, Brian G.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
Curt,

Thank you very much for engaging 🙂

Although I understand what you are saying, from an interop perspective,  
this is not desirable.

In fact, the WPF binding system will see two methods (foo and foo=(val))  
and determine that they are properties that can be bound to. C#, on the  
other hand, can’t use them as properties. Furthermore, if I want a  
simple side effect (like property change notification) in a property, it  
makes sense for me to define my own foo and foo=(val) methods. Again,  
WPF can get these notifications and read the “properties”, but C# just  
sees methods. Another case might be where properties are just wrappers  
around hashes… a case I am running into.

At a very minimum, I would expect to be able to create get\_foo and  
set\_foo(value) in ruby to have them be seen as .Net properties, but this  
doesn’t seem to work either.

In general, I am trying to understand good interop practices between my  
ruby and C# and WPF code, but I can’t seem to make anything other than  
attr\_accessor work.

Brian  
On Thu, Jul 22, 2010 at 9:17 AM, Curt H.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
I believe this works as designed.

The problem is that Ruby doesn’t otherwise distinguish syntactically  
between a property and a method with no parameters. Imagine that you’re  
in tooling such as Visual Studio. By default, the values of properties  
are automatically displayed in the debugger and in tool tips. But if I  
happen to have a no-args method named format\_cdrive, I probably don’t  
want that code to be run just to inspect its value. Effectively,  
attr\_accessor, attr\_reader and attr\_writer are used by IronRuby as  
signals that indicate this operation is free of potentially-nasty side  
effects.

From:  
removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]  
On Behalf Of Brian G.  
Sent: Thursday, July 22, 2010 5:49 AM  
To: removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

So, I haven’t heard anything about this yet on Stack Overflow, or this  
list.

Does anyone know if this is this a bug in IronRuby interop?  
Thanks,  
Brian

On Wed, Jul 21, 2010 at 12:34 PM, Brian G.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
This is a cross-post from Stack Overflow, but I haven’t heard a peep  
there, so I figured I’d try here:

I am playing around with the interop between C# and IronRuby. I have  
noticed that if I define a property in Ruby using `attr_accessor`, it is  
presented to C# as a property. If, on the other hand, I create the  
exact same code manually, it comes back as a method.

For example, take this code:

```
var engine = IronRuby.Ruby.CreateEngine();
string script = @"
  class Test
    attr_accessor :automatic

    def manual
      @manual
    end

    def manual=(val)
      @manual = val
    end

    def initialize
      @automatic = ""testing""
      @manual = ""testing""
    end
  end

  Test.new
";
var testObject = engine.Execute(script);

var automatic = testObject.automatic;
var manual = testObject.manual;

```

When you look at the C# `automatic` variable, the value is a string of  
“testing”. If you look at the C# `manual` variable, it is type  
IronRuby.Builtins.RubyMethod.

Ultimately, I want to create my own properties in Ruby that can be used  
in C#, but I can’t seem to make them be visible as properties like  
`attr_accessor` does.

I THINK, that there is some magic going on in the Module code of the  
Ruby source code (ModuleOps.cs:DefineAccessor). Is there any way to do  
this in Ruby code directly?

Thanks,  
Brian

* * *

Ironruby-core mailing list  
removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[http://rubyforge.org/mailman/listinfo/ironruby-core](http://rubyforge.org/mailman/listinfo/ironruby-core)

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 22, 2010, 9:27pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/9 "2010-07-22T21:27:28Z")

</div>

Awesome! Do you take patches from the community?

Thanks,  
Brian

2010/7/22 Tomas M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 22, 2010, 8:47pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/10 "2010-07-22T20:47:04Z")

</div>

Ability to mark an existing method (pair) as a “property” implementation  
makes sense.  
I’ve added it the feature list:  
[http://ironruby.codeplex.com/workitem/4920](http://ironruby.codeplex.com/workitem/4920)

Tomas

From: removed\_email\_address@domain.invalid  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] On Behalf Of Curt  
Hagenlocher  
Sent: Thursday, July 22, 2010 7:19 AM  
To: removed\_email\_address@domain.invalid  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

I don’t know that you should appreciate anything I say; I haven’t worked  
on IronRuby in over a year. 😃

A long time ago, I wrote code for ICustomTypeDescriptor that does  
property inference based on the presence of arity-0 “foo” and arity-1  
“foo=” but I had assumed that WPF was now binding via IDMOP and not  
ICustomTypeDescriptor. Since this doesn’t work via “dynamic”, I guess  
that’s not the case. Maybe Tomáš has something to add?

From: removed\_email\_address@domain.invalid  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] On Behalf Of Brian G.  
Sent: Thursday, July 22, 2010 7:10 AM  
To: removed\_email\_address@domain.invalid  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

No, that is not sufficient, because it does not work. Assuming the  
example I posted, this code fails:

dynamic automatic = testObject.automatic;  
dynamic manual = testObject.manual;

dynamic autoLength = automatic.Length;  
dynamic manualLength = manual.Length; // RuntimeBinderException

`manual.Length` fails because `manual` is of type  
`IronRuby.Builtins.RubyMethod` and `Length` is not defined.

This is my problem… since ‘manual’ is not exposed to .Net as a  
property, it fails.

Brian

P.S. I REALLY appreciate you talking through this with me.

On Thu, Jul 22, 2010 at 10:01 AM, Curt H.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
WPF binds by effectively treating the Ruby object as “dynamic” - that  
is, it goes through IDynamicMetaObjectProvider. You can get the same  
behavior from C# by saying

dynamic obj = SomeRubyObject();  
dynamic foo = obj.foo;

Is this not sufficient for your needs?

From:  
removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]  
On Behalf Of Brian G.  
Sent: Thursday, July 22, 2010 6:55 AM

To: removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

Thinking on this further, if there were some sort of interop-specific  
class method… like attr\_clr\_property :foo, that caused any methods  
named foo and foo=(var) to be visible to .Net as properties, that would  
be sufficient.

Any thoughts on this?  
B  
On Thu, Jul 22, 2010 at 9:34 AM, Brian G.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
Curt,

Thank you very much for engaging 🙂

Although I understand what you are saying, from an interop perspective,  
this is not desirable.

In fact, the WPF binding system will see two methods (foo and foo=(val))  
and determine that they are properties that can be bound to. C#, on the  
other hand, can’t use them as properties. Furthermore, if I want a  
simple side effect (like property change notification) in a property, it  
makes sense for me to define my own foo and foo=(val) methods. Again,  
WPF can get these notifications and read the “properties”, but C# just  
sees methods. Another case might be where properties are just wrappers  
around hashes… a case I am running into.

At a very minimum, I would expect to be able to create get\_foo and  
set\_foo(value) in ruby to have them be seen as .Net properties, but this  
doesn’t seem to work either.

In general, I am trying to understand good interop practices between my  
ruby and C# and WPF code, but I can’t seem to make anything other than  
attr\_accessor work.

Brian  
On Thu, Jul 22, 2010 at 9:17 AM, Curt H.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
I believe this works as designed.

The problem is that Ruby doesn’t otherwise distinguish syntactically  
between a property and a method with no parameters. Imagine that you’re  
in tooling such as Visual Studio. By default, the values of properties  
are automatically displayed in the debugger and in tool tips. But if I  
happen to have a no-args method named format\_cdrive, I probably don’t  
want that code to be run just to inspect its value. Effectively,  
attr\_accessor, attr\_reader and attr\_writer are used by IronRuby as  
signals that indicate this operation is free of potentially-nasty side  
effects.

From:  
removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]  
On Behalf Of Brian G.  
Sent: Thursday, July 22, 2010 5:49 AM  
To: removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

So, I haven’t heard anything about this yet on Stack Overflow, or this  
list.

Does anyone know if this is this a bug in IronRuby interop?  
Thanks,  
Brian

On Wed, Jul 21, 2010 at 12:34 PM, Brian G.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
This is a cross-post from Stack Overflow, but I haven’t heard a peep  
there, so I figured I’d try here:

I am playing around with the interop between C# and IronRuby. I have  
noticed that if I define a property in Ruby using `attr_accessor`, it is  
presented to C# as a property. If, on the other hand, I create the  
exact same code manually, it comes back as a method.

For example, take this code:

```
var engine = IronRuby.Ruby.CreateEngine();
string script = @"
  class Test
    attr_accessor :automatic

    def manual
      @manual
    end

    def manual=(val)
      @manual = val
    end

    def initialize
      @automatic = ""testing""
      @manual = ""testing""
    end
  end

  Test.new
";
var testObject = engine.Execute(script);

var automatic = testObject.automatic;
var manual = testObject.manual;

```

When you look at the C# `automatic` variable, the value is a string of  
“testing”. If you look at the C# `manual` variable, it is type  
IronRuby.Builtins.RubyMethod.

Ultimately, I want to create my own properties in Ruby that can be used  
in C#, but I can’t seem to make them be visible as properties like  
`attr_accessor` does.

I THINK, that there is some magic going on in the Module code of the  
Ruby source code (ModuleOps.cs:DefineAccessor). Is there any way to do  
this in Ruby code directly?

Thanks,  
Brian

* * *

Ironruby-core mailing list  
removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[http://rubyforge.org/mailman/listinfo/ironruby-core](http://rubyforge.org/mailman/listinfo/ironruby-core)

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 23, 2010, 5:32pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/11 "2010-07-23T17:32:13Z")

</div>

Brian G. wrote:

> Thinking on this further, if there were some sort of interop-specific class  
> method… like attr\_clr\_property :foo, that caused any methods named foo and  
> foo=(var) to be visible to .Net as properties, that would be sufficient.
> 
> Any thoughts on this?

Alternative suggestion: make method redefinition work in this case,  
like this:

```
var engine = IronRuby.Ruby.CreateEngine();
var script = @"
    class Test
      attr_accessor :a, :m

      def m; @m end
      def m=(val) @m = val end

      def initialize; @a, @m = 'automatic', 'manual' end
    end

    Test.new
";
var testObject = engine.Execute(script);

var automatic = testObject.a;
var manual = testObject.m;

Console.WriteLine(automatic);
Console.WriteLine(manual); // should print "manual"
Console.ReadLine();

```

jwm

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 22, 2010, 10:08pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/12 "2010-07-22T22:08:28Z")

</div>

Absolutely.

Tomas

From: removed\_email\_address@domain.invalid  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] On Behalf Of Brian G.  
Sent: Thursday, July 22, 2010 11:50 AM  
To: removed\_email\_address@domain.invalid  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

Awesome! Do you take patches from the community?

Thanks,  
Brian  
2010/7/22 Tomas M.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\>  
Ability to mark an existing method (pair) as a “property” implementation  
makes sense.  
I’ve added it the feature list:  
[http://ironruby.codeplex.com/workitem/4920](http://ironruby.codeplex.com/workitem/4920)

Tomas

From:  
removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]  
On Behalf Of Curt H.  
Sent: Thursday, July 22, 2010 7:19 AM

To: removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

I don’t know that you should appreciate anything I say; I haven’t worked  
on IronRuby in over a year. 😃

A long time ago, I wrote code for ICustomTypeDescriptor that does  
property inference based on the presence of arity-0 “foo” and arity-1  
“foo=” but I had assumed that WPF was now binding via IDMOP and not  
ICustomTypeDescriptor. Since this doesn’t work via “dynamic”, I guess  
that’s not the case. Maybe Tomáš has something to add?

From:  
removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]  
On Behalf Of Brian G.  
Sent: Thursday, July 22, 2010 7:10 AM  
To: removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

No, that is not sufficient, because it does not work. Assuming the  
example I posted, this code fails:

dynamic automatic = testObject.automatic;  
dynamic manual = testObject.manual;

dynamic autoLength = automatic.Length;  
dynamic manualLength = manual.Length; // RuntimeBinderException

`manual.Length` fails because `manual` is of type  
`IronRuby.Builtins.RubyMethod` and `Length` is not defined.

This is my problem… since ‘manual’ is not exposed to .Net as a  
property, it fails.

Brian

P.S. I REALLY appreciate you talking through this with me.

On Thu, Jul 22, 2010 at 10:01 AM, Curt H.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
WPF binds by effectively treating the Ruby object as “dynamic” - that  
is, it goes through IDynamicMetaObjectProvider. You can get the same  
behavior from C# by saying

dynamic obj = SomeRubyObject();  
dynamic foo = obj.foo;

Is this not sufficient for your needs?

From:  
removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]  
On Behalf Of Brian G.  
Sent: Thursday, July 22, 2010 6:55 AM

To: removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

Thinking on this further, if there were some sort of interop-specific  
class method… like attr\_clr\_property :foo, that caused any methods  
named foo and foo=(var) to be visible to .Net as properties, that would  
be sufficient.

Any thoughts on this?  
B  
On Thu, Jul 22, 2010 at 9:34 AM, Brian G.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
Curt,

Thank you very much for engaging 🙂

Although I understand what you are saying, from an interop perspective,  
this is not desirable.

In fact, the WPF binding system will see two methods (foo and foo=(val))  
and determine that they are properties that can be bound to. C#, on the  
other hand, can’t use them as properties. Furthermore, if I want a  
simple side effect (like property change notification) in a property, it  
makes sense for me to define my own foo and foo=(val) methods. Again,  
WPF can get these notifications and read the “properties”, but C# just  
sees methods. Another case might be where properties are just wrappers  
around hashes… a case I am running into.

At a very minimum, I would expect to be able to create get\_foo and  
set\_foo(value) in ruby to have them be seen as .Net properties, but this  
doesn’t seem to work either.

In general, I am trying to understand good interop practices between my  
ruby and C# and WPF code, but I can’t seem to make anything other than  
attr\_accessor work.

Brian  
On Thu, Jul 22, 2010 at 9:17 AM, Curt H.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
I believe this works as designed.

The problem is that Ruby doesn’t otherwise distinguish syntactically  
between a property and a method with no parameters. Imagine that you’re  
in tooling such as Visual Studio. By default, the values of properties  
are automatically displayed in the debugger and in tool tips. But if I  
happen to have a no-args method named format\_cdrive, I probably don’t  
want that code to be run just to inspect its value. Effectively,  
attr\_accessor, attr\_reader and attr\_writer are used by IronRuby as  
signals that indicate this operation is free of potentially-nasty side  
effects.

From:  
removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]  
On Behalf Of Brian G.  
Sent: Thursday, July 22, 2010 5:49 AM  
To: removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Subject: Re: [Ironruby-core] Why does attr\_accessor create a property,  
but method is just a method?

So, I haven’t heard anything about this yet on Stack Overflow, or this  
list.

Does anyone know if this is this a bug in IronRuby interop?  
Thanks,  
Brian

On Wed, Jul 21, 2010 at 12:34 PM, Brian G.  
\<removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:  
This is a cross-post from Stack Overflow, but I haven’t heard a peep  
there, so I figured I’d try here:

I am playing around with the interop between C# and IronRuby. I have  
noticed that if I define a property in Ruby using `attr_accessor`, it is  
presented to C# as a property. If, on the other hand, I create the  
exact same code manually, it comes back as a method.

For example, take this code:

```
var engine = IronRuby.Ruby.CreateEngine();
string script = @"
  class Test
    attr_accessor :automatic

    def manual
      @manual
    end

    def manual=(val)
      @manual = val
    end

    def initialize
      @automatic = ""testing""
      @manual = ""testing""
    end
  end

  Test.new
";
var testObject = engine.Execute(script);

var automatic = testObject.automatic;
var manual = testObject.manual;

```

When you look at the C# `automatic` variable, the value is a string of  
“testing”. If you look at the C# `manual` variable, it is type  
IronRuby.Builtins.RubyMethod.

Ultimately, I want to create my own properties in Ruby that can be used  
in C#, but I can’t seem to make them be visible as properties like  
`attr_accessor` does.

I THINK, that there is some magic going on in the Module code of the  
Ruby source code (ModuleOps.cs:DefineAccessor). Is there any way to do  
this in Ruby code directly?

Thanks,  
Brian

* * *

Ironruby-core mailing list  
removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[http://rubyforge.org/mailman/listinfo/ironruby-core](http://rubyforge.org/mailman/listinfo/ironruby-core)

* * *

Ironruby-core mailing list  
removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[http://rubyforge.org/mailman/listinfo/ironruby-core](http://rubyforge.org/mailman/listinfo/ironruby-core)

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 23, 2010, 5:53pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/13 "2010-07-23T17:53:52Z")

</div>

Brian G. wrote:

> Thinking on this further, if there were some sort of interop-specific class  
> method… like attr\_clr\_property :foo, that caused any methods named foo and  
> foo=(var) to be visible to .Net as properties, that would be sufficient.
> 
> Any thoughts on this?

Good idea. Would it make sense to coordinate with other  
implementations to get some more generic name and semantics?  
Objective-C (and thus MacRuby) also has a notion of properties, right?  
As do JavaBeans.

What about

```
Module#prop_accessor
Module#prop_getter
Module#prop_setter

```

That way, if I have a simple PORO/POCO/POJO that I want to be able to  
interoperate with platform-native code, I only need to switch out  
require ‘clr’ for require ‘java’, but not change any of my other code.  
(Assuming, of course, that the only .NET-specific stuff in my code are  
properties.)

jwm

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 23, 2010, 6:00pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/14 "2010-07-23T18:00:54Z")

</div>

Yes, this is one approached I’ve considered.

What about this case?

```
    class Test
      attr_accessor :a, :m
    end

    class Test2 < Test
      def m; @m end
      def m=(val) @m = val end

      def initialize; @a, @m = 'automatic', 'manual' end
    end

```

And this one?

```
    class Test
      attr_accessor :a, :m
      include M
    end

    class Test2
      include M
    end

    module M
      def m; @m end # should this be a property accessor or 

```

not?  
def m=(val) @m = val end

```
      def initialize; @a, @m = 'automatic', 'manual' end
    end

```

I guess the rule could be that only redefinitions in the same  
class/module transfer the property of being a property accessor.

Another option might be to use attr\_reader/attr\_accessor. If no  
parameters are passed the next method becomes a property accessor. In  
MRI passing no parameters is possible and has no effect.

```
    class Test
      attr_reader
      def m; @m end

      attr_writer # this is not really needed as any method whose 

```

name ends = could automatically be considered a property/indexer setter  
def m=(val) @m = val end

```
      def initialize; @a, @m = 'automatic', 'manual' end
    end

```

Tomas

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 23, 2010, 5:43pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/15 "2010-07-23T17:43:20Z")

</div>

Jorg,

It is a good idea, but I have tried this already, and it still fails.  
By  
re-defining the method after attr\_accessor, you blow away whatever magic  
happens that causes it to be a property at interop time.

Unless… you are suggesting that this is how it SHOULD work.

I think either approach makes sense. A special interop class method is  
nice  
because it is explicit. Having method redefinition do the job is nice  
because it doesn’t require a special class method 🙂

What does everyone else think?

If I get the time, I was planning on getting my hands in the code and  
trying  
to implement it.

Thanks,  
Brian

2010/7/23 Jörg W Mittag  
\<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)

>

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 23, 2010, 6:32pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/16 "2010-07-23T18:32:31Z")

</div>

Brian G. wrote:

> It is a good idea, but I have tried this already, and it still fails.

So did I 🙂

> By  
> re-defining the method after attr\_accessor, you blow away whatever magic  
> happens that causes it to be a property at interop time.
> 
> Unless… you are suggesting that this is how it SHOULD work.

Yes, that’s what I meant.

> I think either approach makes sense. A special interop class method is nice  
> because it is explicit. Having method redefinition do the job is nice  
> because it doesn’t require a special class method 🙂
> 
> What does everyone else think?

Actually, I believe both make sense. Having method redefinition not  
work simply violates at least _my_ Principle of Least Astonishment, so  
it needs to be fixed anyway. But it alone is not enough: sometimes you  
might want to have different names for your .NET property and your  
Ruby methods. A good example might be a readonly boolean property:

```
prop_getter :isValid => :valid?
def valid?
  @is_valid
end

```

Actually, now that I think about it, what about just overloading  
`attr_accessor` and friends? In plain Ruby,

```
attr_reader :isValid => :valid?

```

is illegal anyway. Together with working method redefinition, I  
believe this would cover all use cases, no?

[Note: the risk is that at some time in the future, Ruby might allow  
this notation to have the getter/setter names decoupled from the  
instance variable names. Actually, now that I think about it, I might  
suggest that right now 🙂 It always bugged me that you cannot simply  
define boolean accessors because that would try to create a @valid?  
instance variable, which is illegal.]

jwm

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 23, 2010, 8:03pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/17 "2010-07-23T20:03:15Z")

</div>

Unless CRuby implements properties I don’t like introducing property  
“names” that are different from foo, foo= pattern. For now that’s just  
not the Ruby way.

Tomas

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 23, 2010, 9:28pm UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/18 "2010-07-23T21:28:43Z")

</div>

I agree, I don’t like the idea of doing something that conflicts with  
current Ruby standards.

I do like the prop\_getter idea though, but that is essentially what we  
are talking about with an interop class method. I also have written  
class methods to do the Boolean idea before. Look through my CP\_Bugger  
source to see some examples.

JD

---

<div class="post-metadata">

**Author:** ![bguan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/8edcca/32.png) [@bguan](https://www.ruby-forum.com/u/bguan)\
**Post date:** [July 24, 2010, 4:00am UTC](https://www.ruby-forum.com/t/why-does-attr-accessor-create-a-property-but-method-is-just-a-method/191979/19 "2010-07-24T04:00:57Z")

</div>

So, I was looking at a unit test in the IR source code:

IronRuby.Tests/Runtime/HostingTests.cs:CustomTypeDescriptor1()

It is interesting, because it implies that the getter/setter should be  
implicit based on foo and foo= being defined. The property is  
retrievable  
and even settable via the ICustomTypeDescriptor.GetProperties().

It appears to me that this implicit property should also be be available  
via  
the dynamic invocation without the need to declare it via prop\_accessor.

Am I off base?  
Brian