From: Joel VanderWerf <vjoel@...>
Date: 2004-11-16T07:18:08+09:00
Subject: Re: "The Ruby Way" and adding methods to base classes in libraries

Moses Hohman wrote:
> I have a question about practical experience with adding methods to base 
> classes in libraries. Say I'm writing a library and in a method of that 
> library, I need a method like "first_superset_of", which acts on an 
> array of arrays, and returns the first such array that is a superset of 
> a second array argument's elements, i.e.
> 
> def first_superset_of(arrays, elements)
>     arrays.detect do |array|
>         elements.detect do |element|
>             not array.include?(element) ? false : true
>         end
>     end
> end
> private :first_superset_of
> 
> Now, it's not very object-oriented to add this as a private method in a 
> class that is not an array or an enumerable or whatever and then call it 
> on two arguments. It seems more the ruby way to actually add a method 
> called first_superset_of (and maybe a method called subset_of? for the 
> second inner loop in there) to Enumerable or to Array, and then use that 
> method that way. However, adding this method might clash with another 
> added method in another library that a user might be using, if the 
> author of that other library also created a method on Array or 
> Enumerable with the same name.
> 
> So, what's the right way to handle this situation?

You could define this method in a module and use Object#extend to give 
that functionality to particular arrays.

It doesn't completely prevent conflicts, but it does limit the instances 
that might be affected.