From: 7stud -- <bbxx789_05ss@...>
Date: 2011-04-17T02:14:23+09:00
Subject: Re: What do you do when you need to attach data to an object instance?

Kevin Mahler wrote in post #993207:
> 7stud -- wrote in post #993115:
>> Kevin Mahler wrote in post #992907:
>>>
>>>   def extend_accessor(obj, name)
>>>     obj.singleton_class.module_eval { attr_accessor name }
>>>     obj
>>>   end
>>>
>>
>> Hey, now.  obj.singleton_class is a class, so how about using the
>> synonym class_eval():
>>
>>       obj.singleton_class.class_eval { attr_accessor name }
>
> A class is a module, but a module is not a class.
>

Yes, of course.


>   Class.new.is_a? Module #=>true
>   Module.new.is_a? Class #=>false
>
> Because module_eval and class_eval are aliases, class_eval can be
> called on a module, a situation which is at worst wrong

It certainly isn't "wrong"--ruby allows it.

> and at best
> confusing. module_eval can never be wrong or confusing. Not a hard
> choice.

I thought using module_eval was confusing in your code, and that was why 
I suggested class_eval().

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