# \[ActiveRecord::Base\].collect {|a,b| ...} weirdness

**URL:** <https://www.ruby-forum.com/t/activerecord-base-collect-a-b-weirdness/172091>\
**Category:** Rails\
**Created:** [July 14, 2009, 5:13pm UTC](https://www.ruby-forum.com/t/activerecord-base-collect-a-b-weirdness/172091 "2009-07-14T17:13:42Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![niels\_g](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/71c47a/32.png) [@niels\_g](https://www.ruby-forum.com/u/niels_g)\
**Post date:** [July 14, 2009, 5:13pm UTC](https://www.ruby-forum.com/t/activerecord-base-collect-a-b-weirdness/172091/1 "2009-07-14T17:13:42Z")

</div>

Hey everyone.

My mind has been boggled by an issue I ran into a few hours ago. I am  
completely lost as to why the following code behaves the way it does  
and would appreciate any hints from you guys. It would already be  
super-helpful if others could post their output for the following so  
that I can figure out whether this is weirdness specific to my setup  
or a global phenomenon.

So far, ActiveRecord::Base and its descendants are the only classes  
with which I see this behaviour and furthermore it seems to be limited  
to Ruby 1.9.1.

Mayday!

Thanks,  
Niels (about to dig into array.c)

$ ruby --version; rails --version; ruby \<\<EOR  
require “rubygems”  
gem “activerecord”  
require “activerecord”

puts “\nActiveRecord::Base disappears:”  
[1,String,‘foo’,ActiveRecord::Base].collect {|a,b| puts [a,b].inspect}

puts “\nActiveRecord::Base stays:”  
[1,String,‘foo’,ActiveRecord::Base].collect {|a| puts [a].inspect}

puts “\nwtf?”

EOR  
ruby 1.9.1p129 (2009-05-12 revision 23412) [x86\_64-linux]  
Rails 2.3.2

ActiveRecord::Base disappears:  
[1, nil]  
[String, nil]  
[“foo”, nil]  
[nil, nil]

ActiveRecord::Base stays:  
[1]  
[String]  
[“foo”]  
[ActiveRecord::Base]

wtf?

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<div class="post-metadata">

**Author:** ![niels\_g](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/71c47a/32.png) [@niels\_g](https://www.ruby-forum.com/u/niels_g)\
**Post date:** [July 14, 2009, 8:22pm UTC](https://www.ruby-forum.com/t/activerecord-base-collect-a-b-weirdness/172091/2 "2009-07-14T20:22:29Z")

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I can confirm that this does not happen with ruby 1.8.6 on my machine.  
I don’t have ruby 1.9 installed, so I can’t be much help beyond that.  
Here are my respective outputs with ruby 1.8.6, just as you’d expect:

> > [1,String,‘foo’,ActiveRecord::Base].collect {|a,b| puts [a,b].inspect}  
> > [1, nil]  
> > [String, nil]  
> > [“foo”, nil]  
> > [ActiveRecord::Base, nil]  
> > =\> [nil, nil, nil, nil]
> 
> > [1,String,‘foo’,ActiveRecord::Base].collect {|a| puts [a].inspect}  
> > [1]  
> > [String]  
> > [“foo”]  
> > [ActiveRecord::Base]  
> > =\> [nil, nil, nil, nil]

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<div class="post-metadata">

**Author:** ![niels\_g](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/71c47a/32.png) [@niels\_g](https://www.ruby-forum.com/u/niels_g)\
**Post date:** [July 14, 2009, 9:13pm UTC](https://www.ruby-forum.com/t/activerecord-base-collect-a-b-weirdness/172091/3 "2009-07-14T21:13:56Z")

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Thanks Steve!

I’ve just set up an isolated virtual machine for testing this out a  
bit further. On a vanilla Ubuntu installation with 1.9.1p129 (latest  
stable release) this also occurred. Using a current nightly snapshot  
(of what will probably become 1.9.2) however, everything works as  
expected.

I am still puzzled by this but for the time being happy to just use  
Ruby nightlies. If anyone following Ruby development closely could  
shed some more light on this that would be great though!

Best,  
Niels

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<div class="post-metadata">

**Author:** ![niels\_g](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/71c47a/32.png) [@niels\_g](https://www.ruby-forum.com/u/niels_g)\
**Post date:** [July 15, 2009, 5:57am UTC](https://www.ruby-forum.com/t/activerecord-base-collect-a-b-weirdness/172091/4 "2009-07-15T05:57:02Z")

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Niels G. wrote:  
[…]

> If anyone following Ruby development closely could  
> shed some more light on this that would be great though!

Since this doesn’t seem to be a Rails issue, you will probably have  
better luck attracting the attention of the Ruby core team if you post  
to the Ruby list. Good luck!

> Best,  
> Niels

## Best,

Marnen Laibow-Koser  
[http://www.marnen.org](http://www.marnen.org)  
removed\_email\_address@domain.invalid

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<div class="post-metadata">

**Author:** ![niels\_g](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/71c47a/32.png) [@niels\_g](https://www.ruby-forum.com/u/niels_g)\
**Post date:** [July 15, 2009, 12:03pm UTC](https://www.ruby-forum.com/t/activerecord-base-collect-a-b-weirdness/172091/5 "2009-07-15T12:03:12Z")

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On Jul 15, 5:57 am, Marnen Laibow-Koser \<rails-mailing-l…@andreas-  
[s.net](http://s.net)\> wrote:

> Since this doesn’t seem to be a Rails issue, you will probably have  
> better luck attracting the attention of the Ruby core team if you post  
> to the Ruby list. Good luck!

You are of course right, Marnen. But for the unlikely case that anyone  
else stumbles over this: starting with r24054 (1.9.1-p218) everything  
works as expected again.

Apparently it was an issue with ActiveRecord::Base redefining  
respond\_to? as r24054 is a result of this bug report:  
[http://redmine.ruby-lang.org/issues/show/1723](http://redmine.ruby-lang.org/issues/show/1723)

For those interested, I reproduced the corresponding change below.

Best,  
Niels

— vm\_insnhelper.c (revision  
24053)  
+++ vm\_insnhelper.c (revision  
24054)  
@@ -761,7 +761,7  
@@  
int  
i;  
int argc =  
orig\_argc;  
const int m = iseq-

> argc;

- VALUE  
ary;

- VALUE ary,  
arg0;  
int opt\_pc =  
0;

\*/

- arg0 = argv  
[0];  
if (!(iseq-\>arg\_simple & 0x02) && /\* exclude {|a|}  
_/  
(m + iseq-\>arg\_post\_len) \> 0 && /_ this process is  
meaningful  
\*/

- 

```
       argc == 1 && !NIL_P(ary = rb_check_array_type(argv[0])))

```

{ /\* rhs is only an array  
\*/

- 

```
       argc == 1 && !NIL_P(ary = rb_check_array_type(arg0))) { /

```

- rhs is only an array  
\*/  
th-\>mark\_stack\_len = argc = RARRAY\_LEN  
(ary);

argc);

```
     MEMCPY(argv, RARRAY_PTR(ary), VALUE,

```

argc);  
}

- else  
{
- 

```
   argv[0] =

```

arg0;

- }