Backbone.js model inheritance
I have a basic model
var app = app || {};
app.Era = Backbone.Model.extend({
defaults: {
from: Number.NEGATIVE_INFINITY,
until: Number.POSITIVE_INFINITY,
stash: {
from: null,
until: null
},
_enabled: true
},
toggle: function(){
if(this.get('_enabled')){
this.disable();
}else{
this.enable();
}
this.save();
},
enable: function(){
this.from = this.stash.from;
this.until = this.stash.until;
this.stash.from = null; // strictly speaking unnecssary
this.stash.until = null;
this._enabled = true;
},
disable: function(){
this.stash.from = this.from;
this.stash.until = this.until;
this.from = null;
this.until = null;
this._enabled = false;
},
enabled: function(){
return this._enabled;
},
});
which i am trying to do like this
Name = app.Era.extend({ defaults: { value: '' } });
It seems to work, I don't see any errors in the console. I can even create a new name, but when I try to create a new name, I get an error:
> era = new app.Era()
child
> era.get('from')
-Infinity
> Name = app.Era.extend({ defaults: { value: '' } })
function (){ return parent.apply(this, arguments); }
> name = new Name()
child
> name.get('value')
TypeError: Object [object Object] has no method 'get'
I would appreciate your feedback!
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Edit: This might be a very good answer, but not for this specific question ... The correct answer was provided by Brian Clark. I'll leave this here, even though while I misunderstood your question, it describes a solution to a common problem and might help you anyway.
Base inheritance works by modifying the prototype of the constructor function. When you expand the model and override a property defaults
, it does not merge the property Name.defaults
into Era.defaults
, it just hides it.
Let's consider a simplified example:
var Era = Backbone.Model.extend({ name: "Era" });
var Name = Era.extend({ name: "Name" });
console.log(new Name().name); //-> "name", makes sense, right?
To combine a derived class defaults
with a superclass, you can use what Model.defaults
can be defined as a function as well as an object literal.
var Era = Backbone.Model.extend({
defaults: {
//..
}
});
var Name = Era.extend({
//define defaults as a function
defaults: function() {
//copy the superclass defaults into a new object, and
//then extend that with the new defaults
return _.extend({}, Era.prototype.defaults, {
value:''
});
}
});
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