Ruby - Loops & Iterators !

Loop is the process in which set of instructions or block of codes are repeated in a specified number of times under certain condition is satisfied. for, while, do while are example of loops.

while loop

Ruby while loop is used to execute a program until condition is true, once condition fails execution is terminated from loop. While loop is used when number of needed iterations is not fixed.

count = 0

while count < 5 do
  p count
  count = count+1
end

do while loop

# syntax

loop do
  # some code here
  break if <condition>
end

# Example

i = 1
while true
  puts i
  i = i + 1
  break if i > 5
end

i = 1
loop do
  puts i
  i = i + 1
  break if i > 5
end

for loop

for loop is used to run block of code in a specific number of times when number of needed iterations is known.

for num in 1..100
  puts num
end 

Range loop

Ruby each method is used to iterator over individual item in an array.

(1..100).each do |num|
  puts num
end

# loop through an array using each
[1, 2, 3].each do |i|
  puts i
end

# loop through hash using each
hash_var = {name: 'Car', color: 'Red', model: '2018'}
hash_var.each do |key, value|
  puts "#{key} => #{value}"
end

# find index in loop using each_with_index

[10, 11, 12].each_with_index do |val, key|
  p key
end
=> 0
   1
   2

Times loop

5.times {|i| puts "number #{i}"}

skip iterations with the next keyword

10.times do |i|
  res = i % 2
  next unless res==0

  puts i
end

stop a loop early using break

arr = [2,4,6,8,10,12]
arr.each do |el|
  break if el > 10
  puts el
end