What is a block in Ruby?

A block looks similar to a method in Ruby. Methods consist of a name, but with blocks we don’t need to write a name, and always pass to a method call.

Blocks are a handy and powerful feature in Ruby, and we can use them anywhere.

Blocks are anonymous pieces of code that accept input from arguments and return a value.

Syntax

We can implement Ruby blocks in two ways:

1. Enclosed within do-end statement

Usually, Ruby blocks are implemented within the do-end statement, as they span through multiple lines of code in the program.

block do 
   #statement-1  
   #statement-2  
   #statement-3
   .
   .
end 

2. Enclosed within {} curly braces

We use curly braces to span through a single line of code.

[0, 2, 4].each { |n| puts n }

We can use pipe |: (vertical bars) between two characters to define an argument in a block.

The ‘yield’ statement

We can implement blocks by using the yield statement. We can invoke a yield by passing arguments into the block, too. It calls a block within a method using the yield keyword.

Code

Example 01

Code using do-end statement

Let’s first look at an example of Ruby blocks enclosed within a do-end statement.

Explanation 01

In the above example, the block has an argument n and puts n can be described as the body of our block.

The array is iterated one time because of the each loop and displays the given input.

Example 02

Code using {} braces

Here’s an example code for a Ruby block enclosed within {} curly braces.

Explanation 02

We have used the same array list for this example, but the result generated would be different, as the argument of block asks to display the n + 2th result of each array element.

Example 03

Block using the yield statement

Let’s look at the following code program that uses the yield keyword to display blocks.

Explanation 03

The above program includes a block named yield_block that displays two methods and calls the block outside the loop.