Interfaces in TypeScript provide a powerful way to define contracts for objects and classes. They allow developers to create consistent structures and enforce type-checking across their codebase.

What are Interfaces?

An interface in TypeScript is a blueprint that defines the structure of an object. It specifies the properties and methods that an object should have, without implementing the actual functionality.

Implementing Interfaces

To implement an interface, use the implements keyword followed by the interface name. This ensures that the class adheres to the structure defined by the interface.


interface Animal {
    name: string;
    makeSound(): void;
}

class Dog implements Animal {
    name: string;

    constructor(name: string) {
        this.name = name;
    }

    makeSound(): void {
        console.log("Woof!");
    }
}

Multiple Interface Implementation

TypeScript allows classes to implement multiple interfaces, providing flexibility in design.


interface Swimmer {
    swim(): void;
}

class Dolphin implements Animal, Swimmer {
    name: string;

    constructor(name: string) {
        this.name = name;
    }

    makeSound(): void {
        console.log("Click!");
    }

    swim(): void {
        console.log("Swimming gracefully");
    }
}

Best Practices

Use interfaces to define contracts for objects and classes
Keep interfaces focused and single-purpose
Prefer composition over inheritance when possible
Use Readonly Properties in interfaces for immutable data

Interface vs Abstract Class

While interfaces define a contract, Abstract Classes can provide both a contract and a partial implementation. Choose interfaces when you need pure abstraction without any implementation details.

Advanced Interface Features

TypeScript offers advanced features for interfaces, such as Optional Properties and Extending Interfaces. These features provide additional flexibility when defining complex structures.

Conclusion

Implementing interfaces in TypeScript is a fundamental concept for creating robust, type-safe code. By understanding and utilizing interfaces effectively, developers can build more maintainable and scalable applications.