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TypeScript - interface getter

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Created by:

Richard-Bevan

413

In this article, we would like to show how in TypeScript create getter in interface and later implement it.

W TypeScript nie jest możliwe dodawanie getterów bezpośrednio do interfejsu. W interfejsie można określić tylko właściwość tylko do odczytu.

Quick solution:

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interface Interface {
    readonly getter: string;
}
​
class Implementation implements Interface {
    get getter(): string {
        return 'Some value here ...';
    }
}

Practical example

Edit

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interface Square {
    readonly name: string;
​
    readonly x: number;
    readonly y: number;
}
​
class LocalSquare implements Square {
​
    public constructor(private _name: string, private _x: number = 0, private _y: number = 0) {
        // Nothing here ...
    }
​
    get name(): string {
        return this._name;
    }
​
    get x(): number {
        return this._x;
    }
​
    get y(): number {
        return this._y;
    }
}
​
let a = new LocalSquare('A', 1, 2);
​
console.log(`${a.name}(${a.x}, ${a.y})`);

Complilation and running:

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$ tsc --target ES5 Script.ts
$ node Script.js

Output:

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A(1, 2)

Run it online here.

Notes:

to enable getters support --targer ES5 parameter during complilation is necessary (check full list of targets here)
readonly keyword in interface is optional