[Backbone]2. More detail in Models

Our Appointment model doesn't seem too useful yet. Add two default attributes,

title

as the string

"Checkup"

, and

date

which should default to the current time

new Date()

.

var Appointment = Backbone.Model.extend({
defaults:{
"title": "Checkup",
"date": new Date()
}
});

While messing around in the console, you've discovered a strange bug. Every new

Appointment

you create has the same exact date, instead of the date and time of when the

Appointment

instance was created.

This is because

new Date()

is evaluated once, when the

Appointment

model is first created, and not re-evaluated every time a new instance is created.

To fix this you'll want to assign a function to defaults instead of just a plain object. Wrap the object below in a function which returns the object. This will cause the defaults to get evaluated every time a new instance is created.

var Appointment = Backbone.Model.extend({
defaults : function(){
return {
title: 'Checkup',
date: new Date
}
}
});

Dr. Goodparts finally ponied up for a server and has seeded it with his first few appointments. Luckily for us, he bought the REST package with the JSON add-on.

Point the root URL of your

Appointment

model to the

/appointments

endpoint.

Then, create a new

Appointment

with an

id

of 1, and fetch its data from the server.

var Appointment = Backbone.Model.extend({urlRoot: '/appointments'});
var appointment = new Appointment({id: 1});
appointment.fetch();

Setting the urlRoot of the Appointment model lets us do more than just fetch from the server, it also lets us sync changes made to model instances.

Dr. Goodparts isn't feeling good today so we're going to have to cancel his appointments. Set the appointment's

cancelled

attribute to true and save the appointment to the server.

var appointment = new Appointment({id: 1});
appointment.set("cancelled", true);
//save it to server.
appointment.save();

Dr. Goodparts is upset that he wasn't notified when we changed his last appointment to cancelled.

Add a listener to the

appointment

model instance to pop-up an alert box (using

alert

) whenever any of the model attributes change.

var appointment = new Appointment({id: 1});
appointment.on('change', function(){
alert("Appointment cancelled!");
});

Dr. Goodparts browser crashed because of too many alerts.

Instead of listening for all attribute changes, just listen and alert when changes are made to the

cancelled

attribute.

appointment.on('change:cancelled', function(){
alert("Hey Dr. Goodparts, your appointment has changed!");
});

We've already seen how we can use

get

to access attributes on a model instance, but what if we wanted them all at once?

Use the

console.log

function to log the JSON of the appointment instance using

toJSON

. If you don't remember how

toJSON

works, consult the Backbone Model docs.

var appointment = new Appointment({id: 1});
console.log(appointment.toJSON());

-----------Final Code--------------

//Create a model CLASS
var Appointment = Backbone.Model.extend({
defaults : function(){
return {
title: 'Checkup',
date: new Date()
}
}
});
//Define a object for model
var Appointment = Backbone.Model.extend({urlRoot: '/appointments'});
var appointment = new Appointment({id: 1});
appointment.fetch();
console.log(appointment.toJSON());
/*
appointment.on('change', function(){
alert("Hey Dr. Goodparts, your appointment has changed!");
});*/
appointment.on('change:cancelled', function(){
alert("Hey Dr. Goodparts, your appointment has changed!");
});
/*
If you want to set attribute
appointment.set("cancelled", true);
//save it to server.
appointment.save();
*/
//Create a View CLASS
var AppointmentView = Backbone.View.extend({
render: function(){
var html = '<li>'+this.model.get('title')+'</li>';
$(this.el).html(html);
}
});
//create a view object, include the model instance
var appointmentView = new AppointmentView({model: appointment });
//set title
appointment.set('title', "Nice to meet you!");
//Show the final view
appointmentView.render();
$('#app').html(appointmentView.el);