# Easy Proxy

**URL:** <https://www.ruby-forum.com/t/easy-proxy/174745>\
**Category:** Ruby\
**Created:** [September 1, 2009, 3:52pm UTC](https://www.ruby-forum.com/t/easy-proxy/174745 "2009-09-01T15:52:47Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![robkuz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/34f0e0/32.png) [@robkuz](https://www.ruby-forum.com/u/robkuz)\
**Post date:** [September 1, 2009, 3:52pm UTC](https://www.ruby-forum.com/t/easy-proxy/174745/1 "2009-09-01T15:52:47Z")

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Hi,

it just occurred to me that one sometimes might want to use a proxy  
for an instance variable which restricts access in some way.

class Proc  
def proxy(meth)  
class\<\<self;self;end.send(:alias\_method, meth, :call)  
self  
end  
end

class X  
def initialize  
@e = []  
end

def entries  
en = lambda {|x| @e \<\< x if x \>= 0; en}.proxy(:\<\<)  
end  
end

x = X.new  
x.entries \<\< 10 \<\< -12 \<\< 23  
p x

You can even use it for things like this:

NULL = lambda {|y| y == 0}.proxy :===  
POS = lambda {|y| y \> 0}.proxy :===  
NEG = lambda {|y| y \< 0}.proxy :===

(-2…2).each do |i|  
case i  
when NEG  
puts “#{i} NEG”  
when NULL  
puts “#{i} NULL”  
when POS  
puts “#{i} POS”  
else  
puts “#{i} what?”  
end  
end

Anybody think this should go into the core? (I’m not religious about  
the name.)

Kind regards

robert

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<div class="post-metadata">

**Author:** ![robkuz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/34f0e0/32.png) [@robkuz](https://www.ruby-forum.com/u/robkuz)\
**Post date:** [September 1, 2009, 4:15pm UTC](https://www.ruby-forum.com/t/easy-proxy/174745/2 "2009-09-01T16:15:38Z")

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On Tue, Sep 1, 2009 at 7:52 AM, Robert K.  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)wrote:

> end
> 
> (-2…2).each do |i|  
> end  
> [http://blog.rubybestpractices.com/](http://blog.rubybestpractices.com/)

Very slick and in my opinion highly useful. So, I guess I’m saying yes.

–  
“Hey brother Christian with your high and mighty errand, Your actions  
speak  
so loud, I can’t hear a word you’re saying.”

-Greg Graffin (Bad Religion)

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**Author:** ![robkuz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/34f0e0/32.png) [@robkuz](https://www.ruby-forum.com/u/robkuz)\
**Post date:** [September 1, 2009, 4:19pm UTC](https://www.ruby-forum.com/t/easy-proxy/174745/3 "2009-09-01T16:19:45Z")

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Robert K. wrote:

> Anybody think this should go into the core?

-1, because it’s already easy to add singleton methods and/or build  
proper wrapper classes with delegation - and the latter is usually a  
better solution longer-term (\*)

I do think that \<\< should be more widely implemented: e.g. in Proc as an  
alias for #call, and in Hash for ‘add [key,value] pair’, so it becomes  
more useful for duck-typing. But I don’t think that’s the point you’re  
trying to make here.

Regards,

Brian.

(\*) For example, the ‘entries’ proxy you return currently only  
implements #\<\<. What if you later want it to implement #size or #empty?  
or #first or …

Also, objects with singleton classes cannot be marshaled.

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<div class="post-metadata">

**Author:** ![robkuz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/34f0e0/32.png) [@robkuz](https://www.ruby-forum.com/u/robkuz)\
**Post date:** [September 1, 2009, 4:43pm UTC](https://www.ruby-forum.com/t/easy-proxy/174745/4 "2009-09-01T16:43:45Z")

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2009/9/1 Brian C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> Robert K. wrote:
> 
> > Anybody think this should go into the core?
> 
> -1, because it’s already easy to add singleton methods and/or build  
> proper wrapper classes with delegation - and the latter is usually a  
> better solution longer-term (\*)

The question is whether you always need a long term solution. We’re  
not all building long term applications with Ruby. And if there is a  
feature which makes hacking scripts easier and does not hurt  
application development, then why not?

> I do think that \<\< should be more widely implemented: e.g. in Proc as an  
> alias for #call, and in Hash for ‘add [key,value] pair’, so it becomes  
> more useful for duck-typing. But I don’t think that’s the point you’re  
> trying to make here.

That’s an interesting point! Then I would also ask for === to be an  
alias for Proc#call by default. But wait: and what about +, - etc.?

> (\*) For example, the ‘entries’ proxy you return currently only  
> implements #\<\<. What if you later want it to implement #size or #empty?  
> or #first or …

Then you just exchange the implementation and use Delagator or  
something similar.

> Also, objects with singleton classes cannot be marshaled.

True but I don’t see that as an argument against providing such a  
method. Otherwise Hash would not be allowed a default\_proc either.  
🙂

Kind regards

robert