From: Ilias Lazaridis <ilias@...>
Date: 2005-04-04T02:49:43+09:00
Subject: Re: [EVALUATION] - E03 - jamLang Evaluation Case Applied to Ruby

Saynatkari wrote:
> Le 3/4/2005, "Ilias Lazaridis" <ilias@lazaridis.com> a �crit:
>>Csaba Henk wrote:
>>>On 2005-04-03, Ilias Lazaridis <ilias@lazaridis.com> wrote:
[...]

>>>>but it gives me the basic idea:
>>>>
>>>>class Object
>>>>  def meta() @meta ||= {} end
>>>>end
>>>>
>>>>talker.sayYourName.meta[:author] = "it's just me"
>>>>puts talker.sayYourName.meta[:author]
>>>>=> it's just me
>>>
>>>If you want metadata for the _function_, then it's not exactly the way
>>>to go.
>>>
>>>The sayYourName method, as defined above, is a side-effecting one,
>>>writes out @name, then returns nil, which is a unique object, without
>>>any reference to talker. That is, it's not a possible carrier of
>>>metainformation.
[...]

>>I like the extracted construct - and it works in practice.
[...]

> Just to make sure there is no confusion:
> 
> talker.sayYourName.meta[:author] = "it's just me"
> 
> sayYourName, when evaluated, returns nil. 

This behaviour seems non logical.

talker.sayYourName.meta

talker_object->sayYourName_object->meta_object
Class object   Method object       Hash object

The sayYourName Method Object is not executed, it's just a part of the 
nested datastructure.

> Therefore,
> your meta structure is actually in the instance of
> NilClass, not Talker. You should be able to test it
> by trying nil.meta[:author] after you execute the
> above code.

yes, i've verified this (with the quick test it seemed to work).

I've understood the example you give below.

But I like to have the metadata directly on my function.

And this without further indirection (at least not visual).

> You would want to follow the original example,
> or do something like this (you can elaborate
> on the documentation notation):
> 
> class Object
>   def doc(str)
>     @doc_data ||= {}
>     # caller[1] will be the method name doc() was called from.
>     @doc_data[caller[1]] = str
>   end
> end
> 
> class SomeClass
>   # Some method
>   def some_method
>     doc "This method does something."
>     # ...
>   end
> end

..

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