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Ruby | Types of Iterators
  • Last Updated : 01 Aug, 2018
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The word iterate means doing one thing multiple times and that is what iterators do. Sometimes iterators are termed as the custom loops.

  • “Iterators” is the object-oriented concept in Ruby.
  • In more simple words, iterators are the methods which are supported by collections(Arrays, Hashes etc.). Collections are the objects which store a group of data members.
  • Ruby iterators return all the elements of a collection one after another.
  • Ruby iterators are “chainable” i.e adding functionality on top of each other.

There are many iterators in Ruby as follows:

  1. Each Iterator
  2. Collect Iterator
  3. Times Iterator
  4. Upto Iterator
  5. Downto Iterator
  6. Step Iterator
  7. Each_Line Iterator

    Explaining Types of Iterators

    1. Each Iterator: This iterator returns all the elements of an array or a hash. Each iterator returns each value one by one.
      Syntax:
      collection.each do |variable_name|
         # code to be iterate
      end

      In the above syntax, the collection can be the range, array or hash.
      Example:






      # Ruby program to illustrate each iterator
        
      #!/usr/bin/ruby    
        
      # using each iterator
      # here collection is range
      # variable name is i
      (0..9).each do |i|
            
          # statement to be executed
          puts i
            
      end
        
      a = ['G', 'e', 'e', 'k', 's']
        
      puts "\n"
        
      # using each iterator
      # here collection is an array
      a.each do|arr|
         
          # statement to be executed
          puts arr
            
      end

      Output:

      0
      1
      2
      3
      4
      5
      6
      7
      8
      9
      
      G
      e
      e
      k
      s
      
    2. Collect Iterator: This iterator returns all the elements of a collection. The collect iterator returns an entire collection, regardless of whether it is an array or hash.

      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:




      # Ruby program to illustrate the collect iterator
        
      #!/usr/bin/ruby
        
      a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
        
      # using collect iterator
      # printing table of 5
      b = a.collect{ |y| (5 * y) }
      puts b

      Output:

      5
      10
      15
      20
      25
      30
      35
      40
      45
      50
      
    3. Times Iterator: In this iterator, a loop is implanted with the specific number of time. The loop is initially started from zero and runs until the one less than the specified number.

      This can be used with no iteration variable.. We can add an iteration variable by using the vertical bars around the identifier.
      Syntax:

      t.times do |variable_name|
      
      # code to be execute
      
      end
      

      Here t is the specified number which is used to define the number of iteration.

      Example:






      # Ruby program to illustrate time iterator
        
      #!/usr/bin/ruby
        
      # using times iterator by providing 
      # 7 as the iterate value
      7.times do |i|
          puts i
      end

      Output:

      0
      1
      2
      3
      4
      5
      6
    4. Upto Iterator: This iterator follows top to bottom approach. It includes both the top and bottom variable in the iteration.
      Syntax:
      top.upto(bottom) do |variable_name|
      
      # code to execute
      
      end
      

      Here iteration starts from top and ends on bottom. The important point to remember that the value of bottom variable is always greater than the top variable and if it is not, then it will return nothing.

      Example:




      # Ruby program to illustrate the upto iterator
        
      #!/usr/bin/ruby
        
      # using upto iterator
      # here top value is 4
      # bottom value is 7
      4.upto(7) do |n|   
        puts n   
      end  
        
      # here top > bottom
      # so no ouput
      7.upto(4) do |n|   
        puts n   
      end  

      Output:

      4
      5
      6
      7
      
    5. Downto Iterator: This iterator follows bottom to top approach. It includes both the top and bottom variable in the iteration.
      Syntax:
      top.downto(bottom) do |variable_name|
      
      # code to execute
      
      end
      

      Here iteration starts from bottom and ends on top. The important point to remember that the value of bottom variable is always smaller than the top variable and if it is not, then it will return nothing.

      Example:




      # Ruby program to illustrate the downto iterator
        
      #!/usr/bin/ruby
        
      # using downto iterator
      # here top value is 7
      # bottom value is 4
      7.downto(4) do |n|   
        puts n   
      end  
        
      # here top < bottom
      # so no output
      4.downto(7) do |n|   
        puts n   
      end  

      Output:

      7
      6
      5
      4
      
    6. Step Iterator: Ruby step iterator is used to iterate where the user has to skip a specified range.
      Syntax:
      Collection.step(rng) do |variable_name|
      
      # code to be executed
      
      end 
      

      Here rng is the range which will be skipped throughout the iterate operation.
      Example:




      # Ruby program to illustrate step iterator
        
      #!/usr/bin/ruby
        
      # using step iterator
      # skipping value is 10
      # (0..60 ) is the range
      (0..60).step(10) do|i|
          puts i
      end

      Output:

      0
      10
      20
      30
      40
      50
      60
      
    7. Each_line Iterator: Ruby each_line iterator is used to iterate over a new line in the string.
      Syntax:
      string.each_line do |variable_name|
      
      # code to be executed
      
      end
      

      Example:




      # Ruby program to illustrate Each_line iterator
        
      #!/usr/bin/ruby
         
      # using each_line iterator
      "Welcome\nto\nGeeksForGeeks\nPortal".each_line do|i|
      puts i
      end

      Output:

      Welcome
      to
      GeeksForGeeks
      Portal
      

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