Develop Reference

jQuery updating class variable values not working

I am writing a class in JavaScript for the first time and I am having some trouble writing new data to a class variable. I've been trying all sorts for hours but nothing seems to work!
function ClassName(productId) {
//create variables
this.productId = productId;
this.shop = [];
this.product = [];
//method that calls for response. On success will return {"status" : "success", "shop" : "someshop.com"}
this.auth = function() {
$.ajax({
url: "http://website.com/api/auth/",
dataType: "jsonp",
success: function(data) {
authCallback(data); //use callback to handle response
},
error: function() {
console.log("bad auth");
}
});
}
var authCallback = function(r) {
//using console.log(r) output the response OK
this.shop = r; //this runs with no errors
}
}
Now, as yo can see in the authCallback method I'm setting this.shop = r; but then if i refer back to this variable its still at its default value of [] .
var class = new ClassName(1);
class.auth();
console.log(class.shop); //this outputs []
I've also tried this in the Javascript console writing each line after each stage had been completed(waited for a response from class.auth() and output from authCallback() before then calling console.log(class.shop);
So, what am I doing wrong? Why isn't the variable updating to its new value?

When you just write:
authCallback(data);
then within authCallback you will have the wrong value of this, it'll either be null or the global object (depending on whether you're in strict mode or not).
Use:
success: authCallback.bind(this)
to ensure that this inside the callback actually represents your object.
You should also note that you cannot access this.shop until after the callback has completed. A more idiomatic implementation using modern jQuery techniques would be this:
this.auth = function() {
return $.ajax({
url: "http://website.com/api/auth/",
dataType: "jsonp"
}).done(this.authCallback.bind(this)).fail(function() {
console.log("bad auth");
});
};
this.authCallback = function(r) {
this.shop = r;
return this;
}
followed by:
var clazz = new ClassName(1);
clazz.auth().then(function(c) {
console.log(c.shop);
});

Class method in javascript is not a function

The answer must be obvious but I don't see it
here is my javascript class :
var Authentification = function() {
this.jeton = "",
this.componentAvailable = false,
Authentification.ACCESS_MASTER = "http://localhost:1923",
isComponentAvailable = function() {
var alea = 100000*(Math.random());
$.ajax({
url: Authentification.ACCESS_MASTER + "/testcomposant?" + alea,
type: "POST",
success: function(data) {
echo(data);
},
error: function(message, status, errorThrown) {
alert(status);
alert(errorThrown);
}
});
return true;
};
};
then I instanciate
var auth = new Authentification();
alert(Authentification.ACCESS_MASTER);
alert(auth.componentAvailable);
alert(auth.isComponentAvailable());
I can reach everything but the last method, it says in firebug :
auth.isComponentAvailable is not a function
.. but it is..

isComponentAvailable isn't attached to (ie is not a property of) your object, it is just enclosed by your function; which makes it private.
You could prefix it with this to make it pulbic
this.isComponentAvailable = function() {

isComponentAvailable is actually attached to the window object.

isComponentAvailable is a private function. You need to make it public by adding it to this like so:
var Authentification = function() {
this.jeton = "",
this.componentAvailable = false,
Authentification.ACCESS_MASTER = "http://localhost:1923";
this.isComponentAvailable = function() {
...
};
};

Another way to look at it is:
var Authentification = function() {
// class data
// ...
};
Authentification.prototype = { // json object containing methods
isComponentAvailable: function(){
// returns a value
}
};
var auth = new Authentification();
alert(auth.isComponentAvailable());

Issue with code inner variable

I have a code like the one stated below, please how do I get the value for (getData), using a code like:
var instanceArray = myGraph.getInstances(component)
I was thinking myGraph.getInstances(component).getData will do it, but it failed
this.getInstances = function(component) {
var getData = {};
$.ajax({
url: "/rpc/alerts2/commonObj_rpc.cfc?method=getInstances",
data: {"component":component},
type: "POST",
async: true,
success: function(data) {
getData = $.parseJSON(data);
console.log("hey");
var $render_component_instance = $("#instances").empty();
$("#instances").append($("<option />").val("all").text("All Instances (Summed)"));
$.each(getData, function (cIndex, cItem){
var $instance = $("<option />").val(cItem.si_instance).text(cItem.si_label.toUpperCase());
$render_component_instance.append($instance);
})
$("#instances").multiselect("refresh");
}
});
};`

You can't, the get is asynchronous. getInstances returns before the GET completes, so it's impossible for getInstances to return the data. (See further note below.)
You have (at least) three options:
Use a callback
Return a blank object that will get populated later, and have the code that needs it poll it periodically
Use a synchronous get (not a good idea)
1. Use a callback
What you can do instead is accept a callback, and then call it when the data arrives:
this.getInstances = function(component, callback) {
$.ajax({
url: "/rpc/alerts2/commonObj_rpc.cfc?method=getInstances",
data: {"component":component},
type: "POST",
async: true,
success: function(data) {
var getData = $.parseJSON(data);
console.log("hey");
var $render_component_instance = $("#instances").empty();
$("#instances").append($("<option />").val("all").text("All Instances (Summed)"));
$.each(getData, function (cIndex, cItem){
var $instance = $("<option />").val(cItem.si_instance).text(cItem.si_label.toUpperCase());
$render_component_instance.append($instance);
})
$("#instances").multiselect("refresh");
callback(getData);
}
});
};
And call it like this:
myGraph.getInstances(component, function(data) {
// Use the data here
});
2. Return a blank object that will get populated later
Alternately, you can return an object which will be blank to start with, but which you'll add the data to as a property later. This may be closest to what you were looking for, from your comments below. Basically, there's no way to access a function's local variables from outside the function, but you can return an object and then add a property to it later.
this.getInstances = function(component) {
var obj = {};
$.ajax({
url: "/rpc/alerts2/commonObj_rpc.cfc?method=getInstances",
data: {"component":component},
type: "POST",
async: false, // <==== Note the change
success: function(data) {
var getData = $.parseJSON(data);
console.log("hey");
var $render_component_instance = $("#instances").empty();
$("#instances").append($("<option />").val("all").text("All Instances (Summed)"));
$.each(getData, function (cIndex, cItem){
var $instance = $("<option />").val(cItem.si_instance).text(cItem.si_label.toUpperCase());
$render_component_instance.append($instance);
})
$("#instances").multiselect("refresh");
// Make the data available on the object
obj.getData = getData;
}
});
return obj; // Will be empty when we return it
};
And call it like this:
var obj = myGraph.getInstances(component);
// ...later...
if (obj.getData) {
// We have the data, use it
}
else {
// We still don't have the data
}
3. Use a synchronous get
I do not recommend this, but you could make the call synchronous. Note that synchronous ajax requests will go away in a future version of jQuery. But just for completeness:
this.getInstances = function(component) {
var getData;
$.ajax({
url: "/rpc/alerts2/commonObj_rpc.cfc?method=getInstances",
data: {"component":component},
type: "POST",
async: false, // <==== Note the change
success: function(data) {
var getData = $.parseJSON(data);
console.log("hey");
var $render_component_instance = $("#instances").empty();
$("#instances").append($("<option />").val("all").text("All Instances (Summed)"));
$.each(getData, function (cIndex, cItem){
var $instance = $("<option />").val(cItem.si_instance).text(cItem.si_label.toUpperCase());
$render_component_instance.append($instance);
})
$("#instances").multiselect("refresh");
}
});
return getData;
};
And call it like this:
var getData = myGraph.getInstances(component);
But again, I don't advocate that. Synchronous ajax calls lock up the UI of the browser, leading to a bad user experience.

Making functions wait until AJAX call is complete with jQuery

Im trying to develop a class in JavaScript I can use to access a load of data that is gathered by an AJAX request easily. The only problem is I need to make the members of the class accessible only once the AJAX call is complete. Ideally what I would like to end up is something where by I can call this in a script:
courses.getCourse('xyz').complete = function () {
// do something with the code
}
And this will only fire after the AJAX call has been complete and the data structures in the "class" are ready to be used. Ideally I dont want to have to create a .complete member for every function in the class
Here is the "class" I am trying to make so far:
var model_courses = (function() {
var cls = function () {
var _storage = {}; // Used for storing course related info
_storage.courses = {}; // Used for accessing courses directly
_storage.references = new Array(); // Stores all available course IDs
var _ready = 0;
$.ajax({
type: "GET",
url: "data/courses.xml",
dataType: "xml",
success: function(xml) {
$(xml).find("course").each(function() {
_storage.courses[$(this).attr('id')] = {
title : $(this).find('title').text(),
description : $(this).find('description').text(),
points : $(this).find('points').text()
}
_storage.references.push($(this).attr('id'))
})
}
})
console.log(_storage.courses)
}
cls.prototype = {
getCourse: function (courseID) {
console.log(cls._storage)
},
getCourses: function () {
return _storage.courses
},
getReferences: function (),
return _storage.references
}
}
return cls
})()
At the moment getCourse will be fired before the AJAX request is complete and obviously it will have no data to access.
Any ideas will be greatly appreciated, im stuck on this one!

jQuery already handles this for you using deferred objects, unless i'm misunderstanding what you are looking for.
var courses = {
getCourse: function (id) {
return $.ajax({url:"getCourse.php",data:{id:id});
}
};
courses.getCourse("history").done(function(data){
console.log(data);
});
I know this isn't exactly what you are looking for, I'm hoping it's enough to push you in the right direction. Deferred objects are awesome.

The following changes allow you to make the AJAX request just once and you can call your function like
courses.getCourse('xyz', function(course){
// Use course here
});
Here are the changes
var model_courses = (function() {
// This is what gets returned by the $.ajax call
var xhr;
var _storage = {}; // Used for storing course related info
_storage.courses = {}; // Used for accessing courses directly
_storage.references = []; // Stores all available course IDs
var cls = function () {
xhr = $.ajax({
type: "GET",
url: "data/courses.xml",
dataType: "xml",
success: function(xml) {
$(xml).find("course").each(function() {
_storage.courses[$(this).attr('id')] = {
title : $(this).find('title').text(),
description : $(this).find('description').text(),
points : $(this).find('points').text()
}
_storage.references.push($(this).attr('id'))
});
}
});
}
cls.prototype = {
// Made changes here, you'd have to make the same
// changes to getCourses and getReferences
getCourse: function (courseID, callback) {
if (xhr.readyState == 4) {
callback(_storage.courses[courseID]);
}
else {
xhr.done(function(){
callback(_storage.courses[courseID]);
})
}
},
getCourses: function () {
return _storage.courses
},
getReferences: function (),
return _storage.references
}
}
return cls
})()
As a side note, your module pattern will not work very well if you need to instantiate two of these model_courses objects, since the storage objects are all shared in your self calling function's closure. You usually don't mix the module pattern with prototypes (returning a constructor from a module), unless you really know what you are doing, that is, the shared closure variables work as static properties of your class.
This is what I would do if I were you (since you really want private variables)
function ModelCourses() {
var storage = {
courses: {},
references: []
};
var xhr = $.ajax({
type: "GET",
url: "data/courses.xml",
dataType: "xml",
success: function(xml) {
$(xml).find("course").each(function() {
storage.courses[$(this).attr('id')] = {
title : $(this).find('title').text(),
description : $(this).find('description').text(),
points : $(this).find('points').text()
}
storage.references.push($(this).attr('id'))
})
}
});
this.getCourse = function(courseId, callback) {
function getCourse() {
callback(storage.courses[courseID])
}
if (xhr.readyState == 4) {
getCourse();
}
else {
xhr.done(getCourse);
}
};
}

in getStorage either add a check to see if there is any data to pilfer (preferred), or make the "actual" method private than publicize it when it has items it can access. (I would recommend the first though otherwise you'll get exceptions about calling a method that doesn't exists on an object).

You can define a function getData that would perform the ajax request and that would take the getCourse as a callback.
The getData could possibly store locally the result of the Ajax call and test the local storage before performing the ajax call.
You could also specify a private member to allow the ajax call to be run only once.
You might want to check underscore.js for some handy tool
Here is a short example code :
cls.prototype.getData = function(callback) {
/*perform ajax call or retrieve data from cache*/
callback()
}
cls.prototype.getCourse = function(id) {
this.getData(function() {
/*do something with the data and the id you passed*/
}
}

Specifying a callback in jQuery.ajax to OpenCalais SemanticProxy service

I'm trying to query the OpenCalais service semanticproxy.com. Unfortunately, their url format is as follows:
http://service.semanticproxy.com/processurl/APIKEY/jsonp:handler_function/http://en.wikipedia.org/wiki/Germany
notice that the function callback, is not in a callback=? parameter, but rather follows the response format (jsonp:). This means that I can't use .getJSON, but rather need to use the .ajax method. So I have the following object definition:
function Subject() {
}
Subject.prototype.populate = function(page_title) {
var url = "http://service.semanticproxy.com/processurl/APIKEY/jsonp:handler/http://en.wikipedia.org/wiki/" + page_title;
$.ajax({url: url, dataType: "script", type: "GET", cache: false, callback: null, data: null});
};
var handler = function (data) {
// do stuff with the returned JSON
};
s = new Subject();
s.populate("Germany");
This works fine. But what I really want to do is set properties of my Subject object. But I don't know how to create a function in the context of the Subject that will be able to be used as the callback. i.e:
Subject.prototype.handler = function(data) { this.title = data.title }
Any ideas?

You'd have to set a function on the window object. This is essentially (I think) what jQuery does with its .getJSON method. The below is a bit hacky but hopefully it points you in the right direction:
function Subject() {
}
Subject.prototype.populate = function(page_title) {
// Save context object
var subject = this;
// Create function name like subjectHandler1281092055198
var functionName = "subjectHandler" + new Date().getTime();
window[functionName] = function(data) {
// Invoke function with saved context and parameter
subject.handler.call(subject, data);
}
var url = "http://service.semanticproxy.com/processurl/APIKEY/jsonp:" + functionName + "/http://en.wikipedia.org/wiki/" + page_title;
$.ajax({url: url, dataType: "script", type: "GET", cache: false, callback: null, data: null});
};
Subject.prototype.handler = function (data) {
// do stuff with the returned JSON
};
s = new Subject();
s.populate("Germany");

I don't think you're going to be able to do this, just because of how JSONP works, look at how it actually comes back to the browser, it pretty much does this:
<script type="text/javascript">
handler({ title: "Germany", ...other properties... });
</script>
There's no way to maintain a reference here, you could do one request at a time, or keep an object map for each subject, but there's no way to do it in the JSONP request.
An object map would look something like this:
//delcare this once for the page
var subjects = {};
//do this per subject
var s = new Subject();
s.populate("Germany");
subjects["Germany"] = s;
Then in your hanldler, if any of the data properties is "Germany", you could get it that way, for example:
var handler = function (data) {
var subject = subjects[data.title];
//subject is your Germany subject, use it, go nuts!
};