From: Matt Armstrong <matt+dated+200201151515.88d9fe@...>
Date: 2002-01-11T07:27:18+09:00
Subject: dup, clone, and "deep copy"

I see that Object#dup creates a new object and copies its instance
variables (no deep copy).  Object#clone creates a new object but much
more state is retained (singleton methods, I'm not sure what else).

In sub classes, are there any conventions for how deep a copy dup and
clone should make?  Say I have a class:

    class Foo
        def initialize
            @array = []
            @hash = {}
        end
        
        private
        def dup_self
            @array = @array.dup
            @hash = @hash.dup
            self
        end
    end

I assume that these are reasonable?

    class Foo
        def dup
            temp = super
            temp.dup_self
        end
        def clone
            temp = super
            temp.dup_self
        end
        def deep_dup
            Marshall::load(Marshall::dump(dup))
        end
        def deep_clone
            Marshall::load(Marshall::dump(self))
        end
    end

-- 
matt