From: Joel VanderWerf <vjoel@...>
Date: 2006-10-29T08:01:15+09:00
Subject: Re: hash.collect

Joe Ruby MUDCRAP-CE wrote:
> collect seems to work on a hash:
> 
> h = {'a'=>'1', 'b'=>'2'}
> 
> params = h.collect {|k, v| "#{k}=#{v}"}.join('&')
> 
> Yet collect isn't listed as a method of hash:
> http://www.ruby-doc.org/core
> 
> Is it undocumented, or is some magic going on behind the scenes -- such 
> as the hash getting converted to an array?

The Hash class includes the Enumerable module, which defines #collect in 
terms of #each. In this case, Hash#each yields key,value pairs, so 
#collect does too. It doesn't get converted to an array before map is 
called. It does get converted to an array through the normal behavior of 
#map:

irb(main):003:0> h={1=>2, 3=>4}
=> {1=>2, 3=>4}
irb(main):004:0> h.map
=> [[1, 2], [3, 4]]

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407