Iterators

Iterators are used to do one thing multiple times. They are used in tandem with collections (Hashes, Arrays, etc…). A collection is an object that stores a group of data members.

Each Iterator

Returns all elements in a range, array or hash. Values are returned in the order they are stored in the collection.

letters = ['C', 'o', 'd', 'e', 'c', 'a', 'd', 'e', 'm', 'y']

letters.each do|letter|
  puts letter
end

• Our collection, letters, is an array.
• The each is a method that iterates through the collection.
• The do and end are used to indicate the scope of the each method.
• letter is a variable that is used to store the value of each iteration.

The output would be:

C
o
d
e
c
a
d
e
m
y

Collect Iterator

Runs on all the elements in a collection. Returns the entire collection.

numbers = [1, 2, 3, 4, 5]

numbers_squared = numbers.collect {|number| number * number}

puts numbers_squared
# Output: [1, 4, 9, 16, 25]

• The collect method is a method that iterates through the numbers array.
• number is a variable that is used to store the value of each iteration.

Times Iterator

This iterator is a loop designed to repeat a block of code a certain number of times. May or may not use an iteration variable.

5.times do |i|
  puts "Message number #{i + 1}"
end

• 5.times is the specified number of times to repeat the block of code.

The output would be:

Message number 1
Message number 2
Message number 3
Message number 4
Message number 5