why is there a need to have class methods? in ruby

In Ruby, class methods are used to define behavior that is associated with the class itself, rather than an individual instance of the class (object). There are several reasons why class methods are useful:

1. Organization and encapsulation: Class methods allow you to group related functionality together in a logical and organized manner. By separating class-level behavior from instance-level behavior, you can make your code more modular and easier to manage.

2. Accessing class-level variables: Class methods have direct access to class-level variables, which can be useful when you need to store and retrieve data that is shared across all instances of the class.

3. Utility methods: Class methods are often used to define utility methods that perform common or generic tasks. These methods can be called on the class itself without the need to create an instance of the class.

4. Factories and constructors: Class methods can be used to create instances of the class, acting as factories or alternative constructors. This allows you to define different ways of creating objects without cluttering the instance methods with additional logic.

Here is an example that demonstrates the use of class methods in Ruby:

main.rb
class Car
  @@total_cars = 0

  def initialize
    @@total_cars += 1
  end

  def self.total_cars
    @@total_cars
  end
end

car1 = Car.new
car2 = Car.new

puts Car.total_cars  # Output: 2
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In the example above, the total_cars method is a class method that returns the total number of cars created. It is invoked on the class itself (Car.total_cars) rather than on an instance of the class. This functionality wouldn't be possible without class methods.

Using class methods provides flexibility and allows you to define behavior that is specific to the class as a whole, rather than individual instances.