From: Robert Klemme <bob.news@...>
Date: 2005-04-04T15:14:42+09:00
Subject: Re: [EVALUATION] - E03 - jamLang Evaluation Case Applied to Ruby


"Saynatkari" <ruby-ml@magical-cat.org> schrieb im Newsbeitrag 
news:8yz1QGr1.1112552007.2231070.ruerue@bidwell.textdrive.com...
>
> Le 3/4/2005, "Ilias Lazaridis" <ilias@lazaridis.com> a �crit:
>>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.
>
> You are not accessing the method, you are _calling_ the method.
> As mentioned earlier, talker.method(:sayYourName).meta would
> work.

No, it doesn't.  Method instances are not suited to carrying meta data:

>> class Foo; def bar() end end
=> nil
>> Foo.new.method(:bar).meta[:test]="I'm here"
=> "I'm here"
>> f=Foo.new
=> #<Foo:0x10184008>
>> f.method(:bar).meta[:test]="I'm here"
=> "I'm here"
>> f.method(:bar).meta[:test]
=> nil

The reason is that Method instances are created on each request:

>> f.method(:bar).__id__
=> 134967116
>> f.method(:bar).__id__
=> 134950544
>> f.method(:bar).__id__
=> 134664456
>> f.method(:bar).__id__
=> 134636916

You have to stick to the class or object as point where meta data is stored. 
If you want to store a hash per method you can do

class Object
  def meta() @meta ||= Hash.new{|h,k| h[k]={}} end
end

>> f=Foo.new
=> #<Foo:0x101acf88>
>> f.meta[:bar][:info]="test"
=> "test"
>> f.meta[:bar]
=> {:info=>"test"}
>> f.meta[:bar][:info]
=> "test"

Kind regards

    robert