difference between "each .. do" or "for .. in" loops in rails [duplicate]

Question

Possible Duplicate:
What is “for” in Ruby

Hey. My question is if these loops are the same when I iterate through an Array. Thx for your time!

<% for track in @tracks %>

or

<% @tracks.each do |track| %>

Answer 1

They are different (although it may not matter for your purposes).

for doesn't create a new scope:

blah = %w(foo bar baz)
for x in blah do
   z = x
end
puts z # "baz"
puts x # "baz"

.each creates a new scope for the block:

blah.each { |y| a = y }
puts a # NameError
puts y # NameError

Answer 2

No

For the most part, you probably won't see any differences, but things are quite different in those two cases.

In one case, you have a loop directly in Ruby syntax, in the other case a data structure traversal is periodically yielding to a block.

• return may work differently. If the outer code is in a lambda then return will return from the lambda within the loop but if executed within a block it will return from the enclosing method outside the lambda.
• The lexical scope of identifiers created within the loop is different. (On general principles you really shouldn't create things inside a structured language feature and then use them later outside but this is possible in Ruby with the loop and not with the block.)