From: Richard Dale <Richard_Dale@...>
Date: 2003-07-15T22:37:29+09:00
Subject: Re: Custom method_missing doesn't trap super call

Brian Candler wrote:

> On Tue, Jul 15, 2003 at 07:36:13PM +0900, Richard Dale wrote:
>> >> It looks like you have reinvented the delegator pattern:
>> >> http://www.rubycentral.com/book/lib_patterns.html
>> >> 
>> >> Cheers,
>> >> 
>> >> Brian.
>> >> 
>> >> 
>> > 
>> > Well crap, wouldn't you know... I guess I need to do some more
>> > exploring through Ruby resources.
>> But thanks - I'll experiment with the delegator suggestions - I think
>> this is a fun problem to try and solve somehow..
> 
> Absolutely. I kind of "discovered" delegation too, and found it gives you
> a great way to build objects out of components - much more flexible than
> subclassing, and neatly sidesteps a lot of philosophical issues with
> subclassing too.
I just tried adding this onto the end of the Example 2 of delegation in
Programming Ruby (page 468):

class FooBar < TicketOffice
        def try_delegate_to_super()
                puts "In try_delegate_to_super"
                super
        end
end

to = FooBar.new
puts to.sellTicket
to.try_delegate_to_super

So the superclass of FooBar is a delegator. When I ran it I got the
following output:

ruby trydelegate2.rb
Here is a ticket
In try_delegate_to_super
trydelegate2.rb:33:in `try_delegate_to_super': super: no superclass method
`try_delegate_to_super' (NameError)
        from trydelegate2.rb:39

So although the SimpleDelegate class doesn't use method_missing (my ruby
isn't good enough to tell how it works yet), it isn't possible to forward a
message to super this way either.

-- Richard