Ruby OO-newbie design-question

[Per Wigren]

Hi!
I'm not at all new to programming, I know OO-concepts but I don't have any
hands-on experience with designing/programming OO except for small tests.
I'm also a Ruby newbie, but have been coding a LOT of C, (advanced)
Shellscripts and Python.

I need advice on good design, taking features of Ruby into consideration.

I want a tree of objects like this:

a1
b1
c1
b2
c1
c2
d1

and so on... The a#-objects will hold default values and methods for b# and
b# will hold default values for c# and so on. When a value in a# is changed
I want its children to immediatly inherit them also, if they aren't
overridden. b# will be subclasses of a#, c# will be subclasses of b# etc.
I have to be able to dynamically (at runtime) add and delete children.

What is a good way to design this with the OO-features of Ruby, keeping it
as readable and clean as possible?

Regards,
Per Wigren

[Joe Cheng]

Hi Per,

Unless a, b, and c have different behavior (not just values), I think you
can do it with a single class:

class Node
include Enumerable

def initialize
@parent = nil
@children = []
@values = {}
end

def each(&b)
@children.each &b
end

def add_child(child)
child.parent = self
@children << child
end

def remove_child(child)
child.parent = nil
@children.delete(child)
end

def [](key)
# if the value exists locally, return it; otherwise, if parent
exists, ask it
@values[key] or (@parent and @parent[key])
end

def []=(key, value)
@values[key] = value
end

protected

def parent=(parent)
@parent = parent
end
end

# Then you can do this:
a1 = Node.new
b1 = Node.new
a1.add_child(b1)
c1 = Node.new
b1.add_child(c1)
b2 = Node.new
a1.add_child(b2)
# and so on...

a1['color'] = 'purple'
b1['color'] = 'yellow'
puts b2['color'] # 'purple'
puts c1['color'] # 'yellow'
puts c1['nothing'] # nil

Is that what you had in mind?

"Per Wigren" <wigren@home.se> wrote in message news:3f4f3875_2@127.0.0.1...

> Hi!
> I'm not at all new to programming, I know OO-concepts but I don't have any
> hands-on experience with designing/programming OO except for small tests.
> I'm also a Ruby newbie, but have been coding a LOT of C, (advanced)
> Shellscripts and Python.
>
> I need advice on good design, taking features of Ruby into consideration.
>
> I want a tree of objects like this:
>
> a1
> b1
> c1
> b2
> c1
> c2
> d1
>
> and so on... The a#-objects will hold default values and methods for b#

and

> b# will hold default values for c# and so on. When a value in a# is

changed

> I want its children to immediatly inherit them also, if they aren't
> overridden. b# will be subclasses of a#, c# will be subclasses of b# etc.
> I have to be able to dynamically (at runtime) add and delete children.
>
> What is a good way to design this with the OO-features of Ruby, keeping it
> as readable and clean as possible?
>
> Regards,
> Per Wigren
>