unless and Modifier Conditions

Ruby has two extra ways to write conditions that make simple checks read more naturally.

unless

unless is the opposite of if: the code runs when the condition is false.

logged_in = false

unless logged_in
  puts "Please log in"
end

Please log in

That reads better than if !logged_in. Avoid unless with else or with complicated conditions — double negatives are hard to read.

Modifier form

When the body is a single line, you can put the condition after it:

stock = 0
puts "Out of stock!" if stock.zero?
puts "Order more" unless stock > 5

Out of stock!
Order more

This is extremely common in Ruby code — especially for guard clauses, which exit a method early when something is wrong (you'll see these in the Methods lessons):

return if name.empty?

Common mistakes

• Using the modifier form for long lines. If the statement doesn't fit comfortably on one line, use a normal if ... end block.

Practice

Rewrite this using a modifier unless:

if !password.empty?
  puts "Password set"
end

password = "secret"
puts "Password set" unless password.empty?