Take advantage of the Deferred objects returned by jQuery’s
$.ajax methods. In remotedatastore.js, update the prototype methods so that they return the result of
calling $.get, $.post, and $.ajax.
...
RemoteDataStore.prototype.add = function (key, val) {
return $.post(this.serverUrl, val, function (serverResponse) {
console.log(serverResponse);
});
};
RemoteDataStore.prototype.getAll = function (cb) {
return $.get(this.serverUrl, function (serverResponse) {
console.log(serverResponse);
cb(serverResponse);
});
};
RemoteDataStore.prototype.get = function (key, cb) {
return $.get(this.serverUrl + '/' + key, function (serverResponse) {
console.log(serverResponse);
cb(serverResponse);
});
};
RemoteDataStore.prototype.remove = function (key) {
return $.ajax(this.serverUrl + '/' + key, {
type: 'DELETE'
});
};
...
Because they now return the Deferred produced
by jQuery’s Ajax methods, it is not absolutely necessary
for get and getAll
to accept callbacks. To account for the possibility of no callback, add an if statement to check that cb
was passed in before invoking it.
...
RemoteDataStore.prototype.getAll = function (cb) {
return $.get(this.serverUrl, function (serverResponse) {
if (cb) {
console.log(serverResponse);
cb(serverResponse);
}
});
};
RemoteDataStore.prototype.get = function (key, cb) {
return $.get(this.serverUrl + '/' + key, function (serverResponse) {
if (cb) {
console.log(serverResponse);
cb(serverResponse);
}
});
};
...
Save remotedatastore.js.
Since the RemoteDataStore methods return
Deferreds, you will need to update the Truck
methods to do the same. For now, you will focus on
createOrder and
deliverOrder.
Open truck.js and add a return
to these two methods where you call them on
this.db.
...
Truck.prototype.createOrder = function (order) {
console.log('Adding order for ' + order.emailAddress);
return this.db.add(order.emailAddress, order);
};
Truck.prototype.deliverOrder = function (customerId) {
console.log('Delivering order for ' + customerId);
return this.db.remove(customerId);
};
...
Save truck.js.
Truck now returns the Deferreds that
RemoteDataStore produces.
When using Promises and Deferreds,
it is a best practice to return them from your functions.
Returning them lets any object that
calls createOrder or deliverOrder
register callbacks that are triggered
when the asynchronous work is finished.
In the next section, you will do just that.