The difference between `for` and `each` in Ruby: scope.

gistfile1.md

for should only be used when you actually want the iteratee to be accessible after you leave the block. for pollutes the parent scope with old iteratees. For this reason, each should be your default.

iteration.rb

[1,2,3].each do |i|
  puts "Inside each loop: #{i}"
end

puts "Outside each loop: #{i}" # => undefined local variable or method `i' for main:Object (NameError)

for i in [1,2,3]
  puts "Inside for loop: #{i}"
end

puts "Outside for loop: #{i}" # => prints "Outside for loop: 3"