From: Austin Ziegler <austin@...>
Date: 2003-03-31T14:04:07+09:00
Subject: Re: How to allow iteration over a collection that can be enumerated in multiple ways?

On Mon, 31 Mar 2003 13:34:58 +0900, Sam Roberts wrote:
> I thought of a 3rd way, but I don't know if its too clever.
> 
> Basically, I can write one method, that takes a cond block as its
> argument, and returns a class which defines "each" in terms of
> that condition, and includes enumerable. Now I only have to write
> two methods, and I can let Enumerable do the heavy lifting for me.
> Or is that too clever/confusing?

>> def each_by_group(group) ... for all matches yield(match) end
>> def array_of_group(group) Array.new(all matches...) end

I personally would look at it from an SQL-like perspective.

Enumerable includes a method #find_all or #select which pretty much
does what you want from array_of_group, I think.

  list.select { |obj| select-condition }.each { |e| puts e }
      # => objects matching select-condition have 

If you want to try to combine the methods, I think your 
writing it as "each_by_group" (I would call it "group_each" or
"each_group") is probably the better method.

-austin
-- Austin Ziegler, austin@halostatue.ca on 2003.03.30 at 23:56:50