Control Structures

If Statement

In Ruby, the if statement uses if and end with an optional else or elsif.

energy = 4
if energy > 5
  puts "Great!"
elsif energy == 4
  puts "OK"
else
  puts "Uh Oh!"
end

OK

Since energy is 4, the code prints out "OK".

Ruby Loops

The while loop follows this format:

while condition
   #do stuff here
 end

For example:

counter = 1
while counter <= 5
  puts "iteration #{counter}"
  counter += 1
end

...which prints:

iteration 1
iteration 2
iteration 3
iteration 4
iteration 5

The for loop in Ruby can go through a collection, such as a range, array or hash. It uses the syntax

for item in collection
   #do stuff with item
 end

For example, you can use a for loop and range to print out the same output as before with less code:

for counter in 1..5
  puts "iteration #{counter}"
end

iteration 1
iteration 2
iteration 3
iteration 4
iteration 5

This code printed went through the numbers from 1 to 5 in a range.