From: 7stud -- <bbxx789_05ss@...>
Date: 2007-10-25T09:11:26+09:00
Subject: Re: .each do |foo, bar|     what does bar do?

Thufir wrote:
>
>>From my understanding of a hash, you can iterate through the keys only
> and then find the corresponding bit of the hash.
>

Your understanding is incorrect.

>
> in the
> first line, why are both "real" and "code" part of the interation?
>

Ok, let's get some preliminaries straight:

arr = [1, 2]
a, b = arr
puts a,b

--output:--
1
2

That's a form of what's called 'parallel assignment' in ruby.

The each() method for a hash sends an array consisting of a key/value 
pair to a block:

h = {"a"=>1, "b"=>2}

h.each do |arr|
  p arr
end

--output:--
["a", 1]
["b", 2]


The output shows that each() *assigns* an array to the parameter 
variable 'arr'.  Earlier it was established that parallel assignment can 
be used with arrays.  So that loop can also be written like this:

h = {"a"=>1, "b"=>2}

h.each do |key, val|
  print key, val
  puts
end


 --output:--
a1
b2

As you can see from the output, ruby is perfectly happy to do parallel 
assignment when passing that array to the block.


> Why would this fail:
> 
> code_words.each do |real|
> idea.gsub!( real, code )
> end
> 

For the same reason the following program will fail:

puts code


>
> wouldn't the corresponding code get looked up by during the loop?  
>

How?  In the first instance, you say that it's your understanding that 
when examining a hash with each(), each() will only produce the keys, 
but then you ask why 'code', which is a value, isn't looked up during 
the loop.  So, what exactly is your understanding?

>
> how could the above be changed so that it would work?
> 

code_words.each do |arr|
  idea.gsub!( arr[0], arr[1] )
end
-- 
Posted via http://www.ruby-forum.com/.