CODEWITHSUNDEEP
javascriptinheritancebackbone.js
o01
o01

Reputation: 5440

Default attributes not being set on inherited model in Backbone

I'm trying to build a simple 2D game while learning Backbone, and I'm having difficulties with how inheritance works. Why isn't the default values in EntityModel set? The output from tick() is always:

x: undefined
y: undefined

Simplified code:

$(function(){

EntityModel = Backbone.Model.extend({

    defaults: function(){
        return {
            x : 0,
            y : 0
        };
    },

    tick: function(){
        console.log('x: ' + this.get('x'));
        console.log('y: ' + this.get('y'));
    }

});

PlayerModel = EntityModel.extend({

    defaults: function() {
        return {
            name : 'John Doe',
            health : 10
        };
    },

    initialize: function(options){
        console.log('New player ('+this.get('name')+') entered the game');
    }

});

var player1 = new PlayerModel();

var gameloop = window.setInterval(function(){
    player1.tick();
}, 40);

});

Upvotes: 1

Views: 87

Answers (1)

nikoshr
nikoshr

Reputation: 33344

The defaults declaration in PlayerModel masks the declaration done in its parent class. You have to explicitly incorporate the defaults from EntityModel. For example :

var PlayerModel = EntityModel.extend({
    defaults: function() {
        var defaults_parent = _.result(EntityModel.prototype, 'defaults'),
            defaults_self = {
                name : 'John Doe',
                health : 10
            };

        return _.defaults(defaults_self, defaults_parent);
    }
});

And a demo http://jsfiddle.net/nikoshr/epCsy/

Upvotes: 2

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