How to inject properties and methods of one class into another class?

Question

#javascript #nodejs

I have 3 classes (A, B, C) in my script. Class B extends class A and inside class B is a method which calls a new instance of class C.

Sample Code:

// First class
class A {
    constructor() {
        this.name = 'Eve';
    }

    getName() {
        return this.name;
    }
}

class B extends A {
    constructor(age) {
        this.age = age;
    }

    getAge() {
        return this.age;
    }

    getC() {
        // This is where I needed a solution
        return new C();
    }
}

class C {
    constructor() {
        this.address = 'Market Village';
    }

    getAllInfo() {
        return this;
    }
}

The expected output if run the code below is what it should be:

let b = new B(18);
let info = b.getC().getInfo();
console.log(info); // {address: 'Market Village'}

But what I wanted to happen is for class C to inherit all properties and methods of class A and B so that class C is able to use the properties and methods of both classes.

I've tried several approaches but none works.

Attempt #1:

This approach injects all the properties and methods of class A and B into class C but the problem is it throws an error saying cannot set ... of undefined, for some reason, the methods of class C are not read:

getC() {
    C.calls(this);
}

Attempt #2

This approach reads all the methods of class C and injects all the properties of both class A and B but not its methods. So again, when you call any of the methods of class A and B inside class C, it throws an error:

getC() {
    let _classC = new C();
    Object.assign( _classC, this );

    return _classC;
}

Is there a way to call a new instance of class C and inject all the properties and methods of class B and A?

Note that class C must be a standalone class and should not extend either classes.

Any help is greatly appreciated.

Sorry my bad, noted your comment about not extending the classes just after I commented. Nevermind! — Azer, Mar 13 '19 at 02:30
Yeah, it's complicated but I kind of need it to work that way -: — Irene Mitchell, Mar 13 '19 at 02:57

score 1 · Answer 1 · answered Mar 13 '19 at 02:45

1

Hope this helps:

class A {
    constructor() {
        this.name = 'Eve';
    }

    getName() {
        return this.name;
    }
}

class B extends A {
    constructor(age) {
        super();
        this.age = age;
    }

    getAge() {
        return this.age;
    }

    getC() {
        let _classC = new C();
        Object.assign( _classC, this );

        return _classC;
    }
}

class C {
    constructor() {
        this.address = 'Market Village';
    }

    getInfo() {
        return this;
    }
}
let b = new B(18);
let info = b.getC().getInfo();
console.log(info);

answered Mar 13 '19 at 02:45

Thuc Nguyen

235
2
8

Thanks, but I already tried that approach. It does inject the properties but you can't call any of the methods from class A and B in class C. – Irene Mitchell Mar 13 '19 at 02:58
`let b = new B(18); let c = b.getC(); console.log(c,c.getInfo());` – Thuc Nguyen Mar 13 '19 at 03:42
Yes, that code works. But the other problem is that when calling `this.getAge()` method inside class C, it throws an error. – Irene Mitchell Mar 13 '19 at 04:07
Oh so you want to inheriting "methods"? Hope this helps: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain – Thuc Nguyen Mar 13 '19 at 04:41
And this: https://stackoverflow.com/questions/4777522/javascript-inheritance-and-method-overriding – Thuc Nguyen Mar 13 '19 at 04:43

How to inject properties and methods of one class into another class?

1 Answers1