From: Robert Klemme <shortcutter@...>
Date: 2006-05-07T02:53:46+09:00
Subject: Re: Creating sub-classes using Struct

2006/5/6, Eli Bendersky <eliben@gmail.com>:
> Hello,
>
> There are two Ruby features I want to combine. One is sub-classes (or
> embedded classes):
>
> class Foo
>         def initialize(x)
>                 puts "new Foo #{x}"
>         end
>
>         class Bar
>                 def initialize(y)
>                         puts "new Bar #{y}"
>                 end
>         end
> end
>
>
> joe = Foo::Bar.new(12)    # prints "new Bar 12"
>
>
> Another is dynamic creation of new classes using Struct:
>
> Customer = Struct.new(:name, :address)     #=> Customer
> eddy = Customer.new("Dave", "123 Main")
>
> Here 'Customer' is a class and 'eddy' is an instance of the Customer
> class.
>
> Now, by combining the features, I mean creating a subclass of Foo
> dynamically, using Struct. The following pseudo-code demonstates it
> (pseudo because it obviously doesn't work and only shows what I'm trying
> to do):
>
> class Foo
>         def initialize(x)
>                 puts "new Foo #{x}"
>         end
>
>         Bar = Struct.new(:name, :address)
> end
>
> eddy = Foo::Bar.new("Dave", "123 Main")
>
>
> How can this be done ?

You'll have to modify Struct to be able to create sub classes of
arbitrary classes and not just Object. Btw, if feels a bit strange to
have a nested class that is a sub class of the outer class.  By that
twist it contains itself - I think this is not a good idea.

Kind regards

robert


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