How to Call Proc in Ruby: Syntax and Examples

In Ruby, you call a Proc object using the .call method or the shorthand .() syntax. For example, if you have my_proc = Proc.new { puts 'Hello' }, you can call it with my_proc.call or my_proc.().

Syntax

To call a Proc in Ruby, use either the .call method or the shorthand .() syntax.

• proc_object.call(arguments): Calls the proc with optional arguments.
• proc_object.(arguments): A shorter way to call the proc.

The proc executes the block of code it holds, optionally using any arguments passed.

ruby

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

Output

Hello, Alice!
Hello, Bob!

Example

This example shows how to create a proc that takes a name and prints a greeting. It demonstrates calling the proc using both .call and .() methods.

ruby

greet = Proc.new { |name| puts "Hi, #{name}!" }
greet.call("Emma")
greet.("Liam")

Output

Hi, Emma!
Hi, Liam!

Common Pitfalls

Common mistakes when calling procs include:

• Forgetting to use .call or .() to execute the proc, which means the proc won't run.
• Passing the wrong number of arguments, which can cause errors or unexpected behavior.
• Confusing Proc with lambda, which handle arguments differently.

ruby

wrong_proc = Proc.new { |x, y| puts x + y }

# Wrong: just referencing the proc, no call
wrong_proc

# Right: calling the proc with arguments
wrong_proc.call(2, 3)

Output

5

Quick Reference

Method	Description	Example
.call	Calls the proc with arguments	proc.call(1, 2)
.()	Shorthand to call the proc	proc.(1, 2)
Proc.new	Creates a new proc	Proc.new { |x| x * 2 }

Key Takeaways

Use .call or .() to execute a proc in Ruby.

Pass the correct number of arguments when calling a proc.

Proc.new creates a proc that can be called later.

Forgetting to call the proc means the code inside won't run.

Procs and lambdas differ in argument handling; know which you use.