Overview of loops in Ruby

Fifth article in the Prepare for a Ruby job interview series. In this article, we’ll take a look at the main loops in the Ruby language.

While

As in most programming languages, While will repeat the block passed until the condition is met.

x = 0
while x < 100
  p x
  x +=1 
end

p x +=1 while x < 100 # one-liner

Opposite of While.

x = 0
until x > 50
  p x
  x +=1 
end

p x +=1 until x > 50 # one-liner

Each is the main loop that you’re probably using all the time as a Ruby developer.

[1, 2, 3].each do |i|
   p i
end

Since each is more widely adopted I don’t recommend using for, but here’s how to use it :

for i in [1, 2, 3] do
  p i
end

Times is a shortcut to run a block a defined number of times.

3.times { p 'yes' }
3.times { |i| p i }

Another useful shortcut to run a block through a range of number.

3.upto(5) { |i| p i }

Opposite of Upto.

5.downto(3) { |i| p i }

Will repeat the current iteration if the condition is met.

5.times do |i|
  p i
  redo if i == 4
end

# 0
# 1
# 2
# 3
# 4
# 4
# Infinite loop

Go to the next iteration.

Get out of the current loop before it’s too late!