 Ruby: Loops

Published

There are a lot of different ways to complete a loop. Here's a list of the most popular ones.

Loop

Loop in increments of 2 until x reaches 20.

x = 0

loop do
x += 2
break if x >= 20
puts x
end

Loop through in increments of 2 until you reach 20. If x reaches 6, move on through next if.

x = 0
loop do
x += 2
break if x >= 20
next if x == 6
puts x
end

While Loop

Block-style while

x = 0

while x < 20
x += 2
puts x
end

Single line-style while.

x = 0
puts x += 2 while x < 100

Until

y = 3245
puts y /= 2 until y <= 1

Iterators

Traversing through a fixed set of data

Iterate 5 times.

5.times do
puts "Hello"
end

Up to

Single line style.

1.upto(5) { puts "hello" };

Block style.

1.upto(5) do |i|
puts "hello " + i.to_s
end

This example is similar to the one above with with an explicit each.

1.upto(3).each do |i|
puts "hello " + i.to_s
end

Down to

Single line.

5.downto(1) { puts "hello" };

Each

Use each on a Range.

(1..5).each { puts "hello" };

Present each as a block.

fruits = [ 'banana', 'apple', 'pear' ]
fruits.each do |fruit|
puts fruit.capitalize
end

For In

fruits = [ 'banana', 'apple', 'pear' ]
for fruit in fruits
puts fruit.capitalize
end

This uses for and step to increment by 2 within a range of 0 and 10.

for i in (0..10).step(2) do
puts i
end

Step Iterator

This is really handy if you're doing something like a clock or stopwatch.

(time1..time2).step(15.minutes) do |time|
end

Use Range and go from 0 to 10 in increments of 1.

(0..10).step(1) do |i|
puts "Hello #{i}"
end

Start at one and go to 5 in increments of one.

1.step(5,1) do |i|
puts "Hello #{n}"
end