继承父构造函数参数

Question

I'm browsing the discussion for a similar topic, but can't find my situation...

Am trying call parent constructors with parameters... can't seem to get it right.

I have a PhysicsBody superclass that takes aNode as its only constructor argument:

function PhysicsBody(aNode) {
    this.userData = aNode;
    // ...
}

Of this PhysicsBody inherits a DynamicBody class. Is constructor also takes aNode as only argument... Like I would do it in Java, I'd love to call something equivalent to "super(aNode"); Can't seem to find out how.

Here's the DynamicBody class:

// Wanted to give "new PhysicsBody(this, aNode)", but that fails!
DynamicBody.prototype = new PhysicsBody();
DynamicBody.prototype.constructor=DynamicBody;

function DynamicBody(aNode) {

    // calling the parent constructor fails too:
    // PhysicsBody.prototype.constructor.call(this, aNode);
    //...
}

Answer 1

One way to do it:

function PhysicsBody( aNode ) {
    this.userData = aNode;
}

PhysicsBody.prototype.pbMethod = function () {};

function DynamicBody( aNode ) {
    PhysicsBody.call( this, aNode );
}

// setting up the inheritance
DynamicBody.prototype = Object.create( PhysicsBody.prototype );

DynamicBody.prototype.dbMethod = function () {};

---

Now, when you do

var pb = new PhysicsBody( '...' );

the instance pb gets a userData property and also inherits the methods from PhysicsBody.prototype ( pbMethod in this case).

---

When you do

var db = new DynamicBody( '...' );

the instance db gets a userData property and also inherits the methods from DynamicBody.prototype ( dbMethod in this case), which in turn inherits from PhysicsBody.prototype .

Answer 2

If I understand you correctly, by saying you want to inherit the parent constructor arguments, you mean that new DynamicBody(1, 2, 3) will internally call PhysicsBody(1, 2, 3) for the DynamicBody instance.

This can be accomplished by using .apply and passing arguments along: http://jsfiddle.net/pmkrQ/ .

function DynamicBody() {
    PhysicsBody.apply(this, arguments);
}