如何使用TypeScript构造函数声明变量

Question

I'm trying to use TypeScript constructor in an Angular2 project, and I got confused regarding how to use class constructor to initialize the variables:

function Auto () {
    this.move = function () {
        console.log('move');
    }
    this.stop = function () {
        console.log('stop');
    }
}

Now I will use it in the class:

class Car {
    constructor(private _auto: Auto) {
    }

    onMove() {
        this._auto.move();
    }
}

When I try to compile, I get this error Cannot find name Auto , so could anyone help me understanding what's going on?

And, why private _auto: Auto make _auto a new instance of Auto class?

Update: I know that I can use class to solve the problem, but I want to understand why javascript functions throw this error.

Answer 1

The problem is happening because creating a function does not create a type for the compiler to use, so Auto does not exist as a type. Right now it's only known as the name of a function.

The easiest way to solve this is to use a class for Auto instead:

class Auto {
    move() {
        console.log('move');
    }

    stop() {
        console.log('stop');
    }
}

Then you can do:

let auto = new Auto();
let car = new Car(auto);

---

Alternatively, you could manually describe the type of the function. Here's one example, but don't do this because you should just convert it to a class:

interface AutoConstructor {
    new(): Auto;
}

interface Auto {
    move(): void;
    stop(): void;
}

let Auto: AutoConstructor = function() {
    let self = this as Auto;
    self.move = function () {
        console.log('move');
    }
    self.stop = function () {
        console.log('stop');
    }
} as any;

let auto = new Auto();
let car = new Car(auto); // ok