From: Michael Garriss <mgarriss@...>
Date: 2003-08-01T11:34:34+09:00
Subject: Re: Extracting a parent class

Just in case anyone is following this, I have a new solution to my 
problem.  It only works if each instance variable in the parent class is 
accessable.  Anyone who can solve this or has a hint...plz tell me!  
Here's the test code:

module SuperCastable
    def to_super
        super_obj = self.class.superclass.new
        instance_variables.each { |var|
            begin
                eval "super_obj.#{var[1..-1]} = #{var}"
            rescue NoMethodError
            end
        }
        super_obj
    end
end

class A
    attr_accessor :a
end

class B < A
    include SuperCastable
    attr_accessor :b
end

b = B.new
b.a = "some data"
b.b = "some more data"
a = b.to_super


Daniel Carrera wrote:

>Oh, sorry.
>In that case I don't imagine it's possible by default because in general 
>there might not be an "obvious" way to turn class B into class A.
>
>You should make a B#to_A method.
>
>Cheers,
>Daniel.
>
>On Fri, Aug 01, 2003 at 07:09:07AM +0900, Michael Garriss wrote:
>  
>
>>Sorry...I should have been more clear.  While this works it does not 
>>mantain the state.   I would like all the members of 'b' that are class 
>>A members to be set in 'a'.
>>
>>Daniel Carrera wrote:
>>
>>    
>>
>>>Answer:
>>>a = b.class.superclass.new
>>>
>>>Why:
>>>b.class == B
>>>b.class.superclass == A
>>>b.class.superclass.new == A.new
>>>
>>>Cheers,
>>>Daniel.
>>>
>>>On Fri, Aug 01, 2003 at 06:53:01AM +0900, Michael Garriss wrote:
>>>
>>>
>>>      
>>>
>>>>Sorry about the newbie question but....
>>>>
>>>>class A
>>>>attr_accessor :a
>>>>end
>>>>
>>>>class B < A
>>>>attr_accessor :b
>>>>end
>>>>
>>>>b = B.new
>>>>b.a = "some data"
>>>>b.b = "some more data"
>>>>a = b.?????
>>>>
>>>>How do I set 'a' from 'b' so that a is of class A and not class B?  I 
>>>>don't want the extra info, I want just the subset of members found in 
>>>>the parent class.  Is there a way to cast?
>>>>
>>>>TIA
>>>>Michael Garriss
>>>>
>>>>  
>>>>
>>>>        
>>>>
>>>
>>>      
>>>
>>    
>>
>
>  
>