From: Ilias Lazaridis <ilias@...>
Date: 2005-03-26T10:29:49+09:00
Subject: Re: [EVALUATION] - E03 - jamLang Evaluation Case Applied to Ruby

[from an answer which showed up as a seperate thread]

James Edward Gray II wrote:
> Begin forwarded message:
>
>>> # reflection
>>> class Talker
>>>   # simple
>>>     def sayYourClassName
>>>     puts self.class.name # the 'self' is optional here
>>>   end
>>
>> omitting "self" (puts class.name) leads to an error
>
> I checked this one myself, because it surprised me when you said it.
> You're right of course.  I'm assuming it's because class is a method
> name and a Ruby keyword.

ok

>>>   # advanced
>>>     # caller returns a stack (array) of strings of the form   #
>>> file:linenumber in `method'
>>>   # so we extract the most recent one and parse the method name out
>>>   # code from PLEAC
>>>   def thisMethodName
>>>     caller[0] =~ /in `([^']+)'/ ? $1 : '(anonymous)';
>>>   end
>>
>> I understand the concept.
>>
>> is there possibly a more direct solution available, with cleaner code
>> and a stable/higher execution speed?
>
> Have you measured it and proven it too slow?  Remember, premature
> optimization is the root of all evil in programming.  ;)
>
> I'm not sure what you consider "clean", but getting rid of the ternary
> operator may make it a little more readable:
>
>     if caller[0] =~ /in `([^']+)'/ then $1 else '(anonymous)' end

I meant something direct like:

caller.active_method

>>>   # expert
>>>   def sayYourClassDefinition
>>>     puts "Class:"
>>>     sayYourClassName
>>
>>     puts "Class #{self.class.name}" >> Class Talker
>>
>> but
>>
>>     puts "Class #{sayYourClassName}" >> Talker Class
>>     puts "Class " + sayYourClassName.to_s >> Talker Class
>>
>> why?
>
> In the first example, you're asking Ruby for the class name, which you
> add to a string that gets printed by the local call to puts.  In the
> other two, you're calling a method that prints the class name
> immediately.

Of course [I've overseen the print statements].

> Then the local puts prints "Class " and the return value
> from the method call, which isn't meaningful in this context.

ok

>>>     # %{} is another way to write a string literal
>>
>> #{} - inside strings
>> %{} - outside of strings
>
> No, these are not equivalent.  #{...} is for interpolating Ruby code
> inside a string.  %{...} defined a double quoted string, without the
> quotes:
>
> %{This is a string.  I can use "quotes" in here.  And #{"interpolate"}
> values.}

ok, now I understand.

%{} => string
#{} => string interpolation of code

>>>     # (looks neat for multiline strings)
[...]
>>>     }
>>
>> Can I get somehow a more precise reflection of the class definition
>> (output similar to the original class-def, excluding code)?
>
> I don't believe so, no.  Remember that a Ruby class can be reopened
> and definitions added to it.  That means a class could be built up
> from many places.
>
> Ruby does have a means to get it to store the source code it reads,
> but I don't believe that's what you were asking for.

you're right.

-

I will try to work this out myself.

Where can I find the following information?:

   * An UML diagramm (or another visual representation) of the ruby 
class-model.

   * A deep (but compact) description of the reflection/introspection api's.

> James Edward Gray II

..

-- 
http://lazaridis.com