From: "news.sympatico.qc.ca" <mguay@...>
Date: 2001-08-24T11:50:15+09:00
Subject: [ruby-talk:20239] Re: Inherit singleton method?

First, thank you for your prompt response

The problem is that I would have a copy of the value (attributes) as it was
when 'clone' was invoked.  Instead of having the current state of the object
duplicated, I would prefer having a new object ('initialize' method invoked,
....)

Note: I know, the example is far fetch (object 'x' won't ressemble the class
'OriginalClass' anymore) : just suppose the added attributes and methods (or
changed methods) respect the essence of the original class.  In the
theorical application of singleton methods, I don't want to consider
creating another class (based on, or not based on, the Original class).

# -- beginning of the example (second version)
    class OriginalClass
        attr_accessor :value

        def initialize(value)
            @value = value
        end

        def compute
            @value = @value * 5
        end
    end

    myObj = OriginalClass.new(30)     # myObj.value = 30
    puts myObj.compute                # Expected : 30
    myObj.compute                     # myObj.value = 150

    class << myObj
        def initialize(value)
            @initValue = value
            @value = value
        end
    end

# --> Here : Create the object based on myObj
    secondObj = ???(10)               # secondObj.value = 10, initValue = 10
    puts secondObj.value              # Expected : 10
    secondObj.compute                 # secondObj.value = 50, initValue = 10
    puts secondObj.value              # Expected : 50

    class << myObj
        def compute
            @value = @value + @initValue
        end
    end

    myObj.compute                     # Error: initValue not defined
(suppose we could continue)
    puts myObj.value                  # Expected : 150

# --> Here : Create another object based on myObj
    thirdObj = ???(20)                # thirObj.value = 20, initValue = 20
    puts thirdObj.value               # Expected : 20
    thirdObj.compute                  # thirdObj.value = 40
    puts thirdObj.value               # Expected : 40

    myObj.compute                     # Error: initValue not defined
(suppose we could continue)
    puts myObj.value                  # Expected : 150

    secondObj.compute                 # secondObj.value = 60, initValue = 10
    puts secondObj.value              # Expected : 60

# -- end of example


Finally, would it be possible to CREATE a CLASS based on the actual
methods/attributes of an object?  At first glance, I don't think it's
possible...


Avi Bryant a �crit dans le message ...
>On Fri, 24 Aug 2001, Marco Guay wrote:
>
>> I would like to create, just by curiosity (not a real-life situation), a
new
>> object (like 'otherObj') based on OriginalClass, but with the specific
>> definition of 'x' (new method 'doSomething' included).  By intuition, I
>> could do:
>>     otherObject = x.new            # not very interesting
>> or
>>     otherObject = x.class.new    # if class could be the modified local
copy
>> of the class (if I can say that)
>
>How about:
>      otherObject = x.clone
>
>Avi
>
>