Functions

Functions are a set of instructions that return one value. Functions that exist in an object are typically called methods.

Function Basics

A function is declared using the def keyword. We close a function with the end keyword.

def greeting
  puts "Hello, World!"
  return
end

# Output: Hello, World!
# Output => nil

Functions with Parameters

Functions can take parameters. Parameters are variables that are passed into a function.

def greeting(name)
  puts "Hello, #{name}!"
  return
end

greeting("John")
# Output: Hello, John!
# Output => nil

# Parentheses are optional when calling a function
greeting "Mary"
# Output: Hello, Mary!
# Output => nil

Explicit and Implicit Return

If the return keyword is not used, the last expression in the function will be returned.

def greeting(name)
  return "Hello, #{name}!"
end

greeting("John")
# Output: => Hello, John!

# Returns the value of the last expression evaluated
def greeting(name)
  "Hello, #{name}!"
end

greeting("Mary")
# Output: => Hello, Mary!

Default Values

Default values may be provided and will be used if no argument is passed to our function.

def greeting(name="human")
  return "Hello, #{name}!"
end

greeting
# Output: => Hello, human!