From: Robert Klemme <bob.news@...>
Date: 2005-04-03T21:19:43+09:00
Subject: Re: [EVALUATION] - E03 - jamLang Evaluation Case Applied to Ruby


"Ilias Lazaridis" <ilias@lazaridis.com> schrieb im Newsbeitrag 
news:d2oki2$4m$1@usenet.otenet.gr...
> Robert Klemme wrote:
> [...]
>
>>>>> So, the last question for this part:
>>>>>
>>>>> how can I add runtime-accessible [meta]data to a ruby function 
>>>>> definition?
> [...]
>
>>> I don't understand.
>>>
>>> def talker
>>>
>>>   def sayHello
>>>     puts "Hello World"
>>>   end
>>>
>>>   def sayYourName
>>>     puts @name
>>>   end
>>>
>>> end
>>>
>>> how do I put a "hash" which keeps metadata to each _function_?
>>
>> class Module
>>  def meta() @meta ||= {} end
>> end
>>
>> class Foo
>>  def bar() end
>>  meta[:bar] = "bar_meta"
>> end
> [...]
>
> the above is essentially "class metadata".
>
> 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
>
> [i like this language *very* much]
>
> -
>
> But to understand this fully, can someone please decrypt this:
>
>   def meta()
>     @meta ||= {}
>   end

If @meta is something false (i.e. nil or false) then the expression on the 
right hand side is evaluated and the result is assigned to @meta.  It's 
short for any of these

@meta = {} unless @meta
@meta || (@meta = {})
@meta or @meta = {}

{} creates a hash (synonym for Hash.new, but you can also put values there 
like {"foo"=>"bar"}).

HTH

    robert