class with an expanded base interface incorporated

Question

class with an expanded base interface incorporated

I am struggling with the implementation of an extended interface in a class.

Below is a simplified example (with playground link at the end of the post):

interface A {
    hello:string
}

interface Extension extends A {
    bye:string
}

class Greeting implements Extension {
    constructor(){
        this.hello="hi"
        this.bye= "bye"
    }
}

The error states:

Property 'hello' does not exist on type 'Greeting'.

along with other errors.

I recognize that this is due to the lack of type definition, but why is it necessary when I am already implementing the interface? Is there a more efficient way to achieve this without essentially duplicating the definition of the Extension interface?

The current approach seems logical to me, but I am struggling to grasp the correct procedure. Can you provide guidance?

TSPlayground

typescript

Answer 1

Answer №1

To address the problem at hand, use the code snippet provided below:

...
class Salutation implements Extension {
    // setting up the class variables
    public greeting;
    public farewell;
    
    constructor(){
        this.greeting = "hello";
        this.farewell = "goodbye";
    }
}

Answer 2

To address the problem at hand, use the code snippet provided below:

...
class Salutation implements Extension {
    // setting up the class variables
    public greeting;
    public farewell;
    
    constructor(){
        this.greeting = "hello";
        this.farewell = "goodbye";
    }
}

Answer 3

Answer №2

It is recommended to use classes instead of interfaces in TypeScript because interfaces are just types and do not have any runtime functionality:

class A {
    hello: string
}

class B extends A {
    bye: string
}

class Greeting extends B {
    constructor() {
        super()
        this.hello = "hi"
        this.bye = "bye"
    }
}

Check out the Playground Link for more insights!

Answer 4

It is recommended to use classes instead of interfaces in TypeScript because interfaces are just types and do not have any runtime functionality:

class A {
    hello: string
}

class B extends A {
    bye: string
}

class Greeting extends B {
    constructor() {
        super()
        this.hello = "hi"
        this.bye = "bye"
    }
}

Check out the Playground Link for more insights!

class with an expanded base interface incorporated

TSPlayground

Answer №1

Answer №2

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