Yield and Passing Blocks

Ruby allows passing blocks to methods using the yield keyword.

In this lesson, you will learn how to use yield to execute a block inside a method.

Using Yield

The yield keyword runs the block given to the method.

def greet
  puts 'Before yield'
  yield
  puts 'After yield'
end

greet { puts 'Hello from the block!' }

Passing Parameters with Yield

The yield keyword can pass parameters to the block.

def square(num)
  yield num * num
end

square(4) { |result| puts "Square: #{result}" }

Checking if a Block is Given

You can check if a method received a block using block_given?.

def greet
  if block_given?
    yield
  else
    puts 'No block given'
  end
end

greet

greet { puts 'Hello from block!' }

Passing Blocks with &block

Blocks can be passed explicitly as a parameter using &block.

def execute_block(&block)
  block.call if block
end

execute_block { puts 'Block executed!' }

Using Yield Multiple Times

A method can call yield multiple times.

def repeat(times)
  times.times { yield }
end

repeat(3) { puts 'Hello!' }

Passing Blocks as Procs

Blocks can be converted to Procs and passed as arguments.

def execute_proc(proc)
  proc.call
end

my_proc = Proc.new { puts 'Proc executed!' }
execute_proc(my_proc)

Using Lambda as a Block

A lambda can be used in place of a block.

def execute_lambda(lmbd)
  lmbd.call
end

my_lambda = -> { puts 'Lambda executed!' }
execute_lambda(my_lambda)

Congratulations!

You have learned how to use yield and pass blocks in Ruby.

Next, you will learn about working with collections.