Iterators

Iterators are nothing but methods supported by collections. Objects that store a group of data members are called collections. In Ruby, arrays and hashes can be termed collections.

Iterators return all the elements of a collection, one after the other. We will be discussing two iterators here, each and collect. Let’s look at these in detail.

Ruby each Iterator

The each iterator returns all the elements of an array or a hash.

Syntax

collection.each do |variable|
   code
end

Executes code for each element in collection. Here, collection could be an array or a ruby hash.

Example

#!/usr/bin/ruby

ary = [1,2,3,4,5]
ary.each do |i|
   puts i
end

This will produce the following result −

1
2
3
4
5

You always associate the each iterator with a block. It returns each value of the array, one by one, to the block. The value is stored in the variable i and then displayed on the screen.

Ruby collect Iterator

The collect iterator returns all the elements of a collection.

Syntax

collection = collection.collect

The collect method need not always be associated with a block. The collect method returns the entire collection, regardless of whether it is an array or a hash.

Example

#!/usr/bin/ruby

a = [1,2,3,4,5]
b = Array.new
b = a.collect
puts b

This will produce the following result −

1
2
3
4
5

NOTE − The collect method is not the right way to do copying between arrays. There is another method called a clone, which should be used to copy one array into another array.

You normally use the collect method when you want to do something with each of the values to get the new array. For example, this code produces an array b containing 10 times each value in a.

#!/usr/bin/ruby

a = [1,2,3,4,5]
b = a.collect{|x| 10*x}
puts b

This will produce the following result −

10
20
30
40
50