DEV Community: Palanivel SundaraRajan GugaGuruNathan

Interface Segregation Principle

Palanivel SundaraRajan GugaGuruNathan — Mon, 10 Jun 2024 02:50:07 +0000

The Interface Segregation Principle (ISP) suggests that a class should not be forced to implement methods it doesn’t need.

Bad Practice - Principle not followed


            +------------------+
            |   <<interface>>  |
            |     IVehicle     |
            +------------------+
            | + drive()        |
            | + fly()          |
            +------------------+    
                ^         ^
                |         |               
+------------------+    +------------------+
|      Car         |    |    Airplane      |
+------------------+    +------------------+
| + drive()        |    | + drive()        |
| + fly()          |    | + fly()          |
+------------------+    +------------------+

Good Practice - Principle followed



+------------------+              +------------------+
|   <<interface>>  |              | <<interface>>    |
|      ICar        |              |    IAirplane     |
+------------------+              +------------------+
| + drive()        |              | + fly()          |
+------------------+              +------------------+
        ^                                ^
        |                                |
+------------------+              +------------------+
|      Car         |              |    Airplane      |
+------------------+              +------------------+
| + drive()        |              | + fly()          |
+------------------+              +------------------+
| <<implements>>   |              | <<implements>>   |
|      ICar        |              |    IAirplane     |
+------------------+              +------------------+

Dependency Inversion Principle

Palanivel SundaraRajan GugaGuruNathan — Fri, 07 Jun 2024 16:59:29 +0000

The Dependency Inversion Principle (DIP) states that high level modules(Payment ) should not depend on low level modules(UpiPayment ,CryptoPayment); both should depend on abstractions(PaymentGateway). Abstractions should not depend on details.

public class Payment {
    public void processPayment(UpiPayment upiPayment) {
        // Implementation for processing UPI payment
    }
}

class UpiPayment {
    // UPI payment related properties and methods
}

Tomm you want to add CryptoPayment you need to modify the Payment class this bad .

Good Practice Principle not followed


public class Payment {
    public void processPayment(PaymentGateway paymentGateway) {
        // Implementation for processing payment via PaymentGateway
    }
}

interface PaymentGateway {
    // Payment gateway related methods
}

class UpiPayment implements PaymentGateway {
    // UPI payment related properties and methods
}

class CryptoPayment implements PaymentGateway {
    // Cryptocurrency payment related properties and methods
}