From: Fredrik Jagenheim <fredde@...>
Date: 2003-09-09T17:59:00+09:00
Subject: Need a ruby approach

Hi,

First a little warning, this post is more of a rubberducking session
than a proper question. 

I have a rather trivial problem, but since I'm spending 8 hours a day
cursing C++ and far coding in Ruby, I'm afraid I can't think of a
proper Ruby solution, and instead come up with 'this is how it
could've been done in C++'-solutions.

The problem: I have a data set. I'd like to see if this data set
fullfills certain properties, so I did a couple of classes which will
do the matching against these properties:

def MatchA
    def MatchA.match?(set)
        # Complex calculations on set
        true
    end
end

def MatchB
    def MatchB.match(set)
        # More complex calculations on set
        true
    end
end

Then I'd just do:
puts "It matched A" if MatchA.match?(set)
puts "It matched B" if MatchB.match?(set)

Ok, but now I have 50 of these match classes, so I figured I should
make an array of them:

array_of_match_objects.each{ |match| 
   puts "It matched #{match.name}" if match.match(set) 
}

I would have to change the methods from class to object first, I
guess...

Anyway, then I started to think about using a superclass for these
classes and use Ruby introspection to find all the subclasses and call
match from there. That's when I realized there must be simpler
solution I just can't see...

Perhaps extending the set-class with the methods;

def MatchB
    def match_b?
        # Complex calculation
    end
end

set.extend(MatchB)

puts "Matched B" if set.match_b?

It probably be the best way OO-wise, since it's a property of the Set.

Or am I really wrong here?

//F