CODEWITHSUNDEEP
javascriptinheritanceprototypeobject-create
robinhowlett
robinhowlett

Reputation: 173

Prototypal inheritance: Can you chain Object.create?

I'm new to prototypal inheritance so I'm trying to understand the 'right' way. I thought I could do this:

if (typeof Object.create !== 'function') {
    Object.create = function (o) {
        function F() {}
        F.prototype = o;
        return new F();
    };
}

var tbase = {};

tbase.Tdata = function Tdata() {};

tbase.Tdata.prototype.say = function (data) {
    console.log(data);
};

var tData = new tbase.Tdata();

tbase.BicData = Object.create(tData);

tbase.BicData.prototype.say = function (data) {
    console.log("overridden: " + data)
};

tbase.BicData.prototype.shout = function (data, temp) {
    console.log("SHOUT: " + data + ", " + temp)
};

var test = new tbase.BicData();

tData.say("test1"); 
test.say("test2");
test.shout("test3", "hope");

if (typeof Object.create !== 'function') {
    Object.create = function (o) {
        function F() {}
        F.prototype = o;
        return new F();
    };
}

var tbase = {};

tbase.Tdata = function Tdata() {};

tbase.Tdata.prototype.say = function (data) {
    console.log(data);
};

var tData = new tbase.Tdata();

tbase.BicData = Object.create(tData);

tbase.BicData.prototype.say = function (data) {
    console.log("overridden: " + data)
};

tbase.BicData.prototype.shout = function (data, temp) {
    console.log("SHOUT: " + data + ", " + temp)
};

var test = new tbase.BicData();

tData.say("test1"); 
test.say("test2");
test.shout("test3", "hope");

But instead I get "tbase.BicData.prototype is undefined"

In Java speak, what I want is to have Tdata as a boilerplate 'interface', BicData to be an implementation of that that, and then to instantiate objects from it.

Where am I going wrong?

Upvotes: 6

Views: 1726

Answers (1)

Christian C. Salvadó
Christian C. Salvadó

Reputation: 827476

The problem is that tbase.BicData is an object (tbase.BicData = Object.create(tData);), and the prototype property should be used on constructor functions.

Taking advantage of the Object.create method, I would do something like this:

var tbase = {};

tbase.Tdata = {
  say : function (data) {
    console.log(data);
  }
};

tbase.BicData = Object.create(tbase.Tdata);

tbase.BicData.say = function (data) {
    console.log("overridden: " + data)
};

tbase.BicData.shout = function (data, temp) {
    console.log("SHOUT: " + data + ", " + temp)
};

var test = Object.create(tbase.BicData);
var tData = Object.create(tbase.Tdata);

tData.say("test1"); // test1
test.say("test2"); // overridden: test2
test.shout("test3", "hope"); // SHOUT: test3, hope

Upvotes: 8

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