Is it possible to use getters/setters in interface definition?

Question

At the moment, TypeScript does not allow use get/set methods(accessors) in interfaces. For example:

interface I {
      get name(): string;
}

class C implements I {
      get name(): string {
          return null;
      } 
}

furthermore, TypeScript does not allow using arrow function expressions in class methods, for example:

class C {
    private _name: string;

    get name(): string => this._name;
}

Is there any other way I can use a getter and setter on an interface definition?

Answer 1

You can specify the property on the interface, but you can't enforce whether getters and setters are used, like this:

interface IExample {
    Name: string;
}

class Example implements IExample {
    private _name: string = "Bob";

    public get Name() {
        return this._name;
    }

    public set Name(value) {
        this._name = value;
    }
}

var example = new Example();
alert(example.Name);

In this example, the interface doesn't force the class to use getters and setters, I could have used a property instead (example below) - but the interface is supposed to hide these implementation details anyway as it is a promise to the calling code about what it can call.

interface IExample {
    Name: string;
}

class Example implements IExample {
    // this satisfies the interface just the same
    public Name: string = "Bob";
}

var example = new Example();
alert(example.Name);

And lastly, => is not allowed for class methods - you could start a discussion on Codeplex if you think there is a burning use case for it. Here is an example:

class Test {
    // Yes
    getName = () => 'Steve';

    // No
    getName() => 'Steve';

    // No
    get name() => 'Steve';
}