Control Flow

if/unless, case/when, and loops.

2 min read | Ruby Tutorial

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Control Flow

Ruby gives you plenty of ways to control program flow. if/elsif/else for conditions, or unless for the opposite. You can even use them as one-line modifiers at the end of a line. case/when handles multiple conditions elegantly. Loops? Try while/until, for-in, or the Ruby way: .times and .each. Use break to exit early and next to skip iterations. Everything in Ruby returns a value.

# if / elsif / else
age = 20
if age < 13
  puts "child"
elsif age < 18
  puts "teenager"
else
  puts "adult"
end

# unless — the opposite of if
unless age < 18
  puts "You can vote!"
end

# Modifier form — one-liners
puts "adult" if age >= 18
puts "underage" if age < 18

# case / when
day = "Monday"
case day
when "Monday"
  puts "Start of the week"
when "Friday"
  puts "Almost weekend!"
when "Saturday", "Sunday"
  puts "Weekend!"
else
  puts "Regular day"
end

# while loop
counter = 0
while counter < 5
  puts counter
  counter += 1
end

# until loop — runs while condition is false
counter = 0
until counter == 5
  puts counter
  counter += 1
end

# for-in loop
for i in 1..5
  puts i
end

# .times — the Ruby way
5.times { |i| puts i }

# .each on ranges
(1..5).each { |i| puts i }

# break and next
5.times do |i|
  next if i == 2  # skip 2
  break if i == 4  # stop at 4
  puts i
end
# Output: 0, 1, 3