From: "David A. Black" <dblack@...>
Date: 2007-10-27T20:05:33+09:00
Subject: Re: .each do |foo, bar|     what does bar do?

Hi --

On Sat, 27 Oct 2007, Thufir wrote:

> On Thu, 25 Oct 2007 06:14:12 +0900, Ben Giddings wrote:
>
>> Because "yield" has two arguments, the block you pass each should have
>> two parameters, which it does.  If you used this instead:
>>
>> code_words.each do |foo|
>>   ...
>> end
>>
>> Foo would be assigned an array containing both things sent by "yield",
>> i.e. foo[0] would be the same as real, and foo[1] would be the same as
>> code.
>
>
> I don't see what's wrong with having foo[0] and foo[1], but, yes, it's
> clearer to instead use foo and bar instead.  Ok, that convinces me that
> it's good to do it this way, thank you.
>
> I just can't wrap my mind around *what's* being iterated through.  I
> guess it's the way that, as you put it, the "yield(current_hash_key,
> current_hash_value)" is happening behind the scenes.

Yes, that's correct. yield is a keyword that acts like a method call;
it can have multiple arguments. Blocks can have multiple parameters,
and can therefore be called with multiple arguments.

If you were going to write Hash#each in Ruby, without recourse to
#each, you could write it like this:

class Hash
   def each
     keys = self.keys   # make a 'keys' local variable
     i = 0
     until i == keys.size
       key = keys[i]
       yield(key, self[key])
       i += 1
     end
     self
   end
end


David

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