What Is a Class Method in Ruby: Simple Explanation and Example

A class method in Ruby is a method that belongs to the class itself, not to instances of the class. You call it directly on the class, using self.method_name inside the class definition or by prefixing the method name with the class name.

How It Works

Think of a Ruby class like a blueprint for making objects. Normally, methods inside the class are like instructions for each object made from that blueprint. But a class method is different—it belongs to the blueprint itself, not the objects.

This means you can call a class method without creating an object first. Inside the class, you define a class method by putting self. before the method name. This tells Ruby, "This method is for the class, not for individual objects." It's like having a special tool that only the blueprint can use, not the things made from it.

Example

This example shows a class method that returns the name of the class. Notice how we use self.class_name to define it, and then call it directly on the class.

ruby

class Car
  def self.class_name
    "Car"
  end
end

puts Car.class_name

Output

Car

When to Use

Use class methods when you want to perform actions related to the class as a whole, not to any single object. For example, you might use a class method to create new objects in a special way, keep track of how many objects were made, or provide information about the class itself.

In real life, imagine a factory blueprint that can tell you how many products it has made so far. You don’t need to look at each product; you just ask the blueprint. That’s what class methods do in Ruby.

Key Points

• Class methods belong to the class, not instances.
• Defined with self.method_name inside the class.
• Called directly on the class, like ClassName.method_name.
• Useful for actions related to the class itself, like counting instances or factory methods.

Key Takeaways

Class methods are called on the class itself, not on objects.

Define class methods using self.method_name inside the class.

Use class methods for tasks related to the class as a whole.

Class methods help organize code that doesn’t belong to individual objects.