Blocks, Procs & Lambdas

💎 Ruby Lesson 9 Intermediate

Ruby closures are implemented using Blocks, Procs, and Lambdas, allowing you to pass code snippets to methods as parameters.

1 yield, Procs, and Lambdas Visibility differences

Ruby provides three closure models:

Block: Passed to methods implicitly, and executed using the **`yield`** keyword.
Proc: Saved block objects. Procs do not validate parameter counts, and writing `return` inside a Proc exits the enclosing method immediately.
Lambda: Strict block objects. Lambdas validate parameter counts explicitly, and writing `return` inside a lambda exits only the lambda itself.

2 Closures Code

Let's run a program demonstrating yield operations, Procs, and Lambdas:

Ruby — Closures & Blocks ▶ Run Code

# 1. Method with yield block
def execute_block
  puts "Inside method"
  yield if block_given?
  puts "Exiting method"
end

execute_block { puts "--- Inside block ---" }

# 2. Proc vs Lambda
my_proc = Proc.new { |x, y| puts "Proc parameters: #{x}, #{y}" }
my_proc.call(10) # Ignores missing y parameter smoothly

my_lambda = ->(x, y) { puts "Lambda parameters: #{x}, #{y}" }
# my_lambda.call(10) # Throws ArgumentError! Requires exactly 2 parameters
my_lambda.call(10, 20)

3 Code Challenge

Challenge: Write a method called `perform_math` that yields two numbers to a block. Invoke the method with a block that multiplies the two numbers, and again with a block that adds them.