From: Robert Klemme <bob.news@...>
Date: 2004-05-31T20:58:37+09:00
Subject: Re: How are mixins better than multiple inheritance?


"Georgy" <no.mail@available.net> schrieb im Newsbeitrag
news:PSyuc.5214$%f3.363257@twister.southeast.rr.com...
> Hm, mine outputs "in parent1"
>
> module Parent1
>     def amb_func
>         puts "in parent1"
>     end
> end
>
> module Parent2
>     def amb_func
>         puts "in parent2"
>     end
> end
>
> class Child
>     include Parent1, Parent2
> end
>
> Child.new.amb_func  #=> in parent1

>> Child.ancestors
=> [Child, Parent1, Parent2, Object, Kernel]

That's why.  See:

>> module Parent1
>>     def amb_func
>>         puts "in parent1"
>>     end
>> end
=> nil
>>
?> module Parent2
>>     def amb_func
>>         puts "in parent2"
>>     end
>> end
=> nil
>>
?> class Child1
>>     include Parent1, Parent2
>> end
=> Child1
>>
?> class Child2
>>     include Parent1
>>     include Parent2
>> end
=> Child2
>>
?> Child1.ancestors
=> [Child1, Parent1, Parent2, Object, Kernel]
>> Child2.ancestors
=> [Child2, Parent2, Parent1, Object, Kernel]
>>

Apparently the inclusion sequence differs if you have two separate include
statements vs. one statement with two modules.

Regards

    robert


>
> ___
> Georgy
>
> "Bill Atkins" <dejaspam@batkins.com> wrote in message
news:e6056acc.0405251343.550af715@posting.google.com...
> | Can anyone explain how Ruby's mixin system is better than regular
> | multiple inheritance?  What's the difference between:
> |
> | ----
> |
> | module Parent1
> |     def amb_func
> |         puts "in parent1"
> |     end
> | end
> |
> | module Parent2
> |     def amb_func
> |         puts "in parent2"
> |     end
> | end
> |
> | class Child
> |     include Parent1, Parent2
> | end
> |
> | Child.new.amb_func
> |
> | ----
> |
> | and
> |
> | ----
> |
> | class Parent1
> |     def amb_func
> |         puts "in parent1"
> |     end
> | end
> |
> | class Parent2
> |     def amb_func
> |         puts "in parent2"
> |     end
> | end
> |
> | class Child < Parent1, Parent2
> | end
> |
> | Child.new.amb_func
> |
> | ---
> |
> | Aside from the fact that the second example obviously isn't valid
> | Ruby, how is the first scenario an improvement over the second?  The
> | first outputs "in parent2" and I assume the second would as well.  Can
> | somebody please explain this?
> |
> | Bill
>
>