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Methods and blocks

Define methods with def, keyword arguments, implicit return, blocks with yield, and lambdas.

Runs in Zerethon IDE · Ruby 4.0 Official Ruby documentation ↗
main.rb 
def greet(name, greeting: "Hello")
  "#{greeting}, #{name}!"
end

def stats(numbers)
  [numbers.min, numbers.max, numbers.sum.to_f / numbers.size]
end

def twice
  yield 1
  yield 2
end

puts greet("Ada")
puts greet("Linus", greeting: "Hi")
low, high, mean = stats([4, 8, 6])
puts "#{low} #{high} #{mean}"
twice { |n| puts "block got #{n}" }
square = ->(x) { x * x }
puts square.call(9), square.(3)

Output

Hello, Ada!
Hi, Linus!
4 8 6.0
block got 1
block got 2
81
9
  • A method returns the value of its last expression; return is only needed to leave early.
  • Returning an array and assigning it to several names unpacks it: low, high, mean = stats(...).
  • A block is code passed to a method in { } or do ... end; the method runs it with yield.
  • Method names may end in ? (returns true/false, like even?) or ! (changes the object or is the “dangerous” version, like sort!).

Related topics

Official references