Demo that in Ruby the for expression is just sugar around a call to the each method.

for_calls_each.rb

# Demo that for calls each

class ThreeOf
  def initialize(value)
    @value = value
  end

  def each(&block)
    block.call(@value)
    block.call(@value)
    block.call(@value)
  end
end


collection = ThreeOf.new(99)

for i in collection
  puts i
end

puts "======="

collection.each {|i| puts i}

# And if that doesn't convince you...

class Array
  alias_method :orig_each, :each

  def each(*args, &block)
    puts "Array Each called!"
    orig_each(*args, &block)
  end
end

puts "======="
puts "For loop with array"
for i in [1,2,3]
  puts i
end