From: Robert Klemme <bob.news@...>
Date: 2003-02-11T18:38:10+09:00
Subject: Re: inheriting from base classes


"Phil Tomson" <ptkwt@shell1.aracnet.com> schrieb im Newsbeitrag
news:b2a6o001rma@enews4.newsguy.com...
> I'm much more likely to favor aggregation ('has-a') over inheritance
> ('is-a') - as in the examples above.  You can often use 'method_missing'
> to redirect method calls to the contained object.

I'd support has-a vs. is-a if is-a is not 100% clear. Composition with an
Array is very much simplified by using Enumerable, so the effort to do the
forwarding is very low, because it needs only an implementation of each
like this:

irb(main):109:0> class ArrayContainer
irb(main):110:1>   include Enumerable
irb(main):111:1>
irb(main):112:1*   def initialize()
irb(main):113:2>     @arrayMember = [1,2,3]
irb(main):114:2>   end
irb(main):115:1>
irb(main):116:1*   def each()
irb(main):117:2>     @arrayMember.each {|x| yield x}
irb(main):118:2>   end
irb(main):119:1> end
nil
irb(main):120:0>
irb(main):121:0* a = ArrayContainer.new
#<ArrayContainer:0x2aafa10 @arrayMember=[1, 2, 3]>
irb(main):122:0> a.to_a
[1, 2, 3]
irb(main):123:0> a.each { |x| p x }
1
2
3
[1, 2, 3]
irb(main):124:0>

Regards

    robert