How to Create a Proc in Ruby: Syntax and Examples

In Ruby, you create a Proc using Proc.new or the proc method followed by a block of code. This creates a reusable block of code that you can call later with call.

Syntax

A Proc is created by calling Proc.new or proc with a block. The block contains the code you want to reuse. You can then run the proc using call.

• Proc.new { |args| ... }: Creates a new Proc object.
• proc { |args| ... }: Another way to create a Proc.
• call(args): Runs the Proc with optional arguments.

ruby

my_proc = Proc.new { |name| puts "Hello, #{name}!" }
my_proc.call("Alice")

Output

Hello, Alice!

Example

This example shows how to create a Proc that takes a number, doubles it, and prints the result. Then it calls the Proc with different numbers.

ruby

doubler = proc { |x| puts x * 2 }
doubler.call(5)
doubler.call(10)

Output

10
20

Common Pitfalls

One common mistake is forgetting to use call to run the Proc. Another is confusing Procs with lambdas, which handle arguments and returns differently.

Also, using Proc.new without a block raises an error.

ruby

wrong_proc = Proc.new
# Raises error: no block given (LocalJumpError)

correct_proc = Proc.new { puts "This works!" }
correct_proc.call

Output

This works!

Quick Reference

Action	Syntax	Description
Create Proc	Proc.new { |args| ... }	Creates a new Proc object with a block
Create Proc	proc { |args| ... }	Alternative way to create a Proc
Call Proc	proc_object.call(args)	Runs the Proc with given arguments
Check Proc	proc_object.is_a?(Proc)	Returns true if object is a Proc

Key Takeaways

Create a Proc in Ruby using Proc.new or proc with a block.

Run a Proc by calling its call method with arguments.

Always provide a block when creating a Proc to avoid errors.

Procs are reusable blocks of code that can take parameters.

Remember Procs differ from lambdas in argument handling and return behavior.