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Looping with Ruby

Ruby Assignment Operators

Assignment operators in Ruby are used to assign or update values to variables. The most common assignment operator is = but others also exist, like +=, -=, *= and /=.

a = 1;
a += 3;
puts a; # Output: 4


b = 4;
b -= 2;
puts b; # Output: 2


num = 12;
num *= 2;
puts num; # Output: 24


num /= 4;
puts num; # Output: 6

Ruby each Method

To iterate over an array in Ruby, use the .each method. It is preferred over a for loop as it is guaranteed to iterate through each element of an array.

data = [3, 6, 9, 12]


data.each do |num|
  puts "The number is: #{num}"
end


# Output:
# The number is: 3
# The number is: 6
# The number is: 9
# The number is: 12

Ruby “next” Keyword

In Ruby, the next keyword is used within a loop to pass over certain elements and skip to the following iteration. It is useful for omitting elements that you do not wish to have iterated. next is followed by an if statement which defines which elements are to be skipped.

for i in 1..10
  next if i % 2 == 0
  puts i
end


# In this example, the next 
# keyword along with a shorthand 
# if statement is used to skip 
# over the even numbers in the sequence.
  
# Output:
# 1
# 3 
# 5
# 7
# 9

Ruby while Loop

Putting a block of code in a while loop in Ruby will cause the code to repeatedly run the code as long as its condition is true.

If the block of code doesn’t have a way for the condition to be changed to false, the while loop will continue forever and cause an error.

i = 1


while i <= 3 do
  puts "Message number #{i}"
  i = i + 1
end


# Output:
# Message number 1
# Message number 2
# Message number 3

Ruby times Method

To execute the same block of code a set a number of times in Ruby, use the times method.

5.times { puts "Codecademy" }


# Output: 
# Codecademy
# Codecademy
# Codecademy
# Codecademy
# Codecademy

Ruby Range

In ruby, a sequence of integers can be demonstrated by a range. The range can be divided into an inclusive range where the last integer in the sequence is included and an exclusive range where the last integer is excluded.

# Inclusive
(3..5).each do |i|
  puts i
end
# Output:
# 3
# 4
# 5


# Exclusive
(3...5).each do |i|
  puts i
end
# Output
# 3
# 4

Ruby loop

A loop method can be used to run a block of code repeatedly in Ruby. Either use curly braces ({}) or the do/end keyword combination to wrap the block of code that will be looped.

num = 1
loop do
  puts "We are in the loop!"
  num += 1
  break if num > 3
end


puts "We have exited the loop!"


# Output
# We are in the loop!
# We are in the loop!
# We are in the loop!
# We have exited the loop!

Ruby until Loop

Putting a block of code inside an until loop in Ruby will cause the code to run as long as its condition remains false. It’s only when the condition becomes true that the loop stops.

If the block of code doesn’t allow for a way for the condition to be changed to true then the loop will continue forever and it will cause an error.

i = 1


until i == 4 do
  puts "Message number #{i}"
  i = i + 1
end


# Output
# Message number 1
# Message number 2
# Message number 3

Ruby for Loop

A block of code can be repeated a set amount of times with the for loop in Ruby.

for i in 1..3 do
  puts "Message number #{i}"
end


# Output
# Message number 1
# Message number 2
# Message number 3

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