From: "David A. Black" <dblack@...>
Date: 2008-09-02T18:14:26+09:00
Subject: Re: Self and Current Class

Hi --

On Tue, 2 Sep 2008, Pedro Silva wrote:

> Thomas, thanks for your reply.
>>
>> So I guess the general rule is: inside module declaration, both self and
>> current class are set to the module we're declaring. Outside module
>> declarations, current class is set to the eigenclass of self.
>>
>> I hope this is not a complete mess and rubbish :)
>
> Consider this case:
>
>  class SomeClass
>    # self is SomeClass, current class is SomeClass
>    puts "Class Level - #{self}"
>
>    def some_method
>      # self is an instance, current class is SomeClass
>      puts "Some Method - #{self}"
>
>      def self.some_inside_class_method
>        # self is an instance, current class is instance's singleton
> class
>        puts "Inside class method - #{self}"

That's not a class method. self is an instance of SomeClass; you're
defining a singleton method on that instance. Every time you do:

   def obj.something

you're defining a singleton method "something" on obj. self is just an
alias for a particular object at a particular point in runtime.

>      end
>
>      def some_inside_instance_method
>        # self is an instance, current class is SomeClass
>        puts "Inside instance method - #{self}"
>      end

I'm not sure what you mean by "inside" in the method name. It's just
an instance method.

>      # self is an instance, current class is instance's singleton class
>      instance_eval { puts "Instance instance_eval - #{self}" }
>      # no class_eval for instances
>    end
>
>    def self.class_method
>      # self is SomeClass, current class is SomeClass's singleton class
>      puts "Class method - #{self}"
>    end
>
>    # self is SomeClass, current class is SomeClass's singleton class
>    instance_eval { puts "Class instance_eval - #{self}" }
>
>    #  self is SomeClass, current class is SomeClass
>    class_eval { puts "Class class_eval - #{self}" }
>  end
>
> Are all the comments correct about self and current class value and are
> all cases covered (current class modification)?
> Is def the only method that uses the current class value?

It's a keyword, rather than a method, but I think it is the only thing
that cares about the notion of "current class", at least as I
understand that notion. (I admit it's not one that I've paid much
attention to, by that name, though of course I like to know what 'def'
will do at any given time.)


David

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