Inner Classes in TypesScript

Example of Inner Classes in Typescript

(available since 1.6)

The implementation method is actually "class expressions".

We use them to create a private "inner class" (e.g. myClassExpresion) which is instantiated with the parent class's this and assigned to a public property of the parent class (e.g. innerClassInstance).

Unfortunately, the "inner class" does not have access to private or protected members of the parent.

class Greeter {
    constructor(message: string) {
        this.greeting = message;
    }

    //inner class definition
    private myClassExpresion = class {
        constructor(private parent: Greeter){}
        public say(x: number) {
            return this.parent.greet() + " " + x;
        }
    }

    public greet() {
        return "Hello, " + this.greeting;
    }

    // inner class instance
    public innerClassInstance = new this.myClassExpresion(this);

    private greeting: string;
}

// USAGE
let greeter = new Greeter("I am number");
alert(greeter.innerClassInstance.say(9));

note: the inner class must be defined within the parent class before it is instantiated.