Blocks, Procs, and Lambdas

Ruby provides powerful ways to handle reusable pieces of code using blocks, Procs, and Lambdas.

In this lesson, you will learn how to use these concepts effectively.

What is a Block?

A block is a piece of code enclosed between do ... end or curly braces { ... }.

[1, 2, 3].each do |num|
  puts num * 2
end

Single-Line Blocks

For simple operations, you can use curly braces {} instead of do ... end.

[1, 2, 3].each { |num| puts num * 2 }

Passing Blocks to Methods

Blocks can be passed to methods like each, map, and times.

5.times { puts 'Hello, Ruby!' }

What is a Proc?

A Proc is an object that stores a block of code and can be executed later.

say_hello = Proc.new { puts 'Hello from Proc!' }
say_hello.call

Passing Arguments to a Proc

Procs can take arguments just like methods.

square = Proc.new { |num| num * num }
puts square.call(4)

What is a Lambda?

A lambda is similar to a Proc but has stricter argument checking.

greet = ->(name) { puts "Hello, #{name}!" }
greet.call('Alice')

Differences Between Proc and Lambda

• Procs ignore extra arguments, while Lambdas enforce them.
• Lambdas return control to the calling method, while Procs exit immediately.

proc_example = Proc.new { return 'Proc Exited' }
lambda_example = -> { return 'Lambda Executed' }

def test
  puts proc_example.call
  puts lambda_example.call
end

test

Congratulations!

You have learned how to use blocks, Procs, and Lambdas in Ruby.

Next, you will explore the yield keyword and passing blocks dynamically.