Ruby Iterators - each & collect


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 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 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 following result:

      10
      20
      30
      40
      50