From: Robert Klemme <shortcutter@...>
Date: 2007-10-03T18:55:03+09:00
Subject: Re: how to add an iterator to a class?

On 24.09.2007 05:42, David B. Williams wrote:
> Mike Steiner wrote:
>> I have a simple class (this is just an example, so ignore any syntax or
>> style errors):
>>
>> class MyArray
>>     def initialize
>>         @a = Array.new
>>     end
>>     def Push( item )
>>         @a.push( item )
>>     end
>>     def GetArray
>>         return @a
>>     end
>> end
>>
>> And I have this code:
>>
>> myarray = MyArray.new
>> myarray.Push( 1 )
>> myarray.Push( 2 )
>>
>> myarray.GetArray.each do | i |
>>     puts i
>> end
>>
>> So my question is: How do I replace GetArray with something more 
>> elegant,
>> that gives MyArray a method named .each that I can call directly?
>>
>> Michael Steiner
> 
> Hi Michael,
> 
> What you want to do is mixin the Enumerable module into your class:
> 
> http://www.ruby-doc.org/core/classes/Enumerable.html
> 
> You then have to define an #each method that yields for each member of 
> your collection.
> 
> For example:
> 
> class MyArray
>   include Enumerable
> 
>   def initialize
>     @a = Array.new
>   end
> 
>   def each
>     for e in @a do
>       yield e
>     end
>   end
> end

In this simple case (i.e. without filtering or converting) you can even 
do this:

def each(&b)
   @a.each(&b)
   self
end

Also note that conventionally #each returns self.

Kind regards

	robert