Block syntax (do..end and curly braces) in Ruby

Introduction

Blocks let you group code to run later or multiple times. They make your code cleaner and easier to reuse.

When you want to repeat actions for each item in a list.

When you want to run some code only inside a method call.

When you want to pass a small piece of code to another method.

When you want to organize your code clearly without making a new method.

Syntax

Ruby

method_name do
  # code here
end

# or

method_name { # code here }

Use do..end for multi-line blocks.

Use curly braces { } for single-line blocks.

Examples

This prints "Hello" three times using do..end block.

Ruby

3.times do
  puts "Hello"
end

This does the same as above but uses curly braces for a single-line block.

Ruby

3.times { puts "Hi" }

This goes through each number and prints double its value using do..end.

Ruby

numbers = [1, 2, 3]
numbers.each do |n|
  puts n * 2
end

Same as above but with curly braces for a short block.

Ruby

numbers.each { |n| puts n * 2 }

Sample Program

This program counts from 1 to 5 using a do..end block and then prints fruit names in uppercase using a curly braces block.

Ruby

5.times do |i|
  puts "Count: #{i + 1}"
end

["apple", "banana", "cherry"].each { |fruit| puts fruit.upcase }

Important Notes

Blocks are anonymous chunks of code you can pass to methods.

Curly braces have higher precedence than do..end, so use them carefully in complex expressions.

Blocks can take parameters inside pipes | | to use values from the method.

Summary

Blocks group code to run inside methods.

Use do..end for multi-line blocks and { } for single-line blocks.

Blocks can take parameters to work with data from the method.