Understanding the Differences Between Inheritance and Delegates: Avoiding Duplicate Code in Object-Oriented Programming

How do delegate objects lead to duplicate code, and how does this compare to inheritance?

class Shape {
    void draw() {
        // Drawing logic
    }
}

class Circle extends Shape {
    void draw() {
        // Circle drawing logic
        super.draw();
    }
}

class Drawer {
    private Shape shape;
    Drawer(Shape shape) {
        this.shape = shape;
    }
    void drawShape() {
        shape.draw();
    }
}

When designing object-oriented software, developers often choose between inheritance and delegation. This decision can significantly affect code maintainability and duplication. Inheritance allows derived classes to inherit characteristics from a base class, while delegation involves using another object's functionality. Understanding these patterns is crucial to avoiding duplicate code.

class Vehicle {
    void start() {
        // Start logic
    }
}

class Car extends Vehicle {
    void start() {
        // Car specific start logic
        super.start();
    }
}

class EngineRelayer {
    private Vehicle vehicle;
    EngineRelayer(Vehicle vehicle) {
        this.vehicle = vehicle;
    }
    void start() {
        vehicle.start();
    }
}

Causes

• Use of inheritance without proper class hierarchy.
• Overlooking the encapsulation benefits of delegation.
• Relying on multiple inheritance leading to the diamond problem.

Solutions

• Implement a clear and concise class hierarchy to minimize redundancy.
• Leverage composition through delegation as an alternative to inheritance.
• Ensure that common functionalities are abstracted in a base class where feasible.

Mistake: Using multiple inheritance in languages that support it leads to complex code structures.

Solution: Prefer interface-based design to achieve multiple behaviors without redundancy.

Mistake: Implementing similar methods in different classes instead of abstracting them into a base class.

Solution: Identify common behaviors and extract them into a base class or utility class.