Which Class Should Be Responsible for a Method in Object-Oriented Programming?

In object-oriented programming (OOP), how do I determine which class should own a specific method?

Determining which class should own a method in OOP involves understanding the responsibilities and relationships of the classes involved. Proper method ownership leads to better code organization, maintainability, and adherence to the principles of OOP such as encapsulation and single responsibility.

class Car {
    private int speed;

    public void accelerate(int increment) {
        speed += increment;
    }
}

class Driver {
    private String name;

    public void drive(Car car) {
        car.accelerate(10);
    }
}

Causes

• The method's functionality relates closely to the data or functionality of a particular class.
• Multiple classes share common functionality, necessitating a decision on where to encapsulate a method.
• Complex dependencies between classes may require breaking down responsibilities into smaller units.

Solutions

• Identify the primary responsibility of each class involved to determine method ownership.
• Use principles of OOP such as Encapsulation and the Single Responsibility Principle to decide on method placement.
• Consider code reuse and avoid duplication by placing shared methods in a common superclass or utility class.

Mistake: Assigning methods to classes that do not logically align with their responsibilities.

Solution: Always align methods with classes that naturally handle the data or behavior concerning those methods.

Mistake: Forgetting to consider the principle of code reuse, leading to method duplication in multiple classes.

Solution: Refactor common methods into a base class or a standalone utility class to promote reusability.