I have a Backbone Collection class with the url property set to a method.
The url is comprised of 3 "elements" which I have called baseUrl, username and path - so it would look something like baseUrl/username/path
I use the same instance for several users in the spa I am working on. However the one element I want to be able to change (after instantiation) is the username. I need this for 2 reasons.
1st - I don't have the username property at instantiation time.
2nd - The username changes depending on the user and I don't want to create new instances of the collection for every new user.
So my issue is why does the url method not take parameters after instantiating the collection so that I could do something like myCollection.url({username: "Mac"})?
Also why does Backbone not allow for parameters to be passed into the url method?
Backbone calls the url method with the collection as the context, so you can access member variables of your collection instance with this.
var MyCollection = Backbone.Collection.extend({
url: function() {
return "base-url/" + this.username + "/path";
},
});
To use this after instanciation, you could set the username field of your collection manually or you could override the sync method of your collection.
var MyCollection = Backbone.Collection.extend({
url: function() {
return "base-url/" + this.username + "/path";
},
sync: function(method, model, options) {
options = options || {};
if (options.username) this.username = options.username;
// call the default sync
return Backbone.collection.prototype.sync.call(this, method, model, options);
}
});
And use it:
myCollection.fetch({ username: "Mac" });
Additional information on how to know how url is called
I'm an avid user of the annotated source of Backbone and it's really important as a lot of Backbone's features are undocumented and the sources are small and easy to go through.
If you check the sync method, you should see that line:
params.url = _.result(model, 'url') || urlError();
And if you check the underscore's result function, you can see that it calls the function (passed as a string) like this:
return _.isFunction(value) ? value.call(object) : value;
Related
I’m trying to understand how and where to use data after a fetch using Backbone.js but I’m a little confused.
I’ll explain the situation.
I have an app that, on the startup, get some data from a server. Three different kind of data.
Let’s suppose Airplanes, Bikes, Cars.
To do that, I’ve inserted inside the three collections (Airplanes, Cars, Bikes) the url where to get these data.
I’ve overwrited the parse method, so I can modify the string that I get, order it, and put it in an object and inside localstorage. I need it to be persistent because I need to use those 3 data structure.
So with a fetch i get all those data and put them inside localstorage. Is it correct doing it that way?
Now i need to make other calls to the server, like “get the nearest car”.
In the view i need to see the color, name and model of the car, all that informations are inside the object “Cars” in localstorage.
In my view “showcars.view” I just call a non-backbone js, (not a collection, model or view) where i get all the informations i need. In this js i do:
var carmodel = new Car(); //car is the backbone model of the cars
carmodel.url = '/get/nearest/car'; //that give id of the nearest car
carmodel.fetch ({
success: function () {}
//here i search the Cars object for a car with the same id
//and get name, color, model and put them in sessionstorage
})
So after that call, in the view I can get the data I need from the sessionstorage.
Is that a bad way of doing things? If so, how i should fetch and analyze those informations? I should do all the calls and operations inside the models?
Thanks
This would be the way that you might implement what you want.
var Car = Backbone.Model.extend();
var Cars = Backbone.Collection.extend({
model: Car,
url: '.../cars'
});
var NearestCar = Backbone.Model.extend({
url: '...nearest/car'
});
var cars = new Cars();
var nearestCar = new NeaerestCar();
cars.fetch({
success: function() {
nearestCar.fetch({
success: function(model) {
var oneYouWant = cars.get(model.get('id'));
// do something with your car
// e.g.:
// var carView = new CarView({model: oneYouWant});
// $('body').append(carView.render().el);
});
});
});
});
In general, Backbone keeps everything in memory (that is, the browser memory) so there is no need to save everything to local storage, as long as your Collection object is somehow reachable from the scope you are sitting in (to keep things simple let's say this is the global window scope).
So in your case I will have something like three collections:
window.Cars
window.Airplanes
window.Bikes
Now you want the nearest. Assuming you are in a Backbone View and are responding to an event, in your place I would do something like this (just shows the meaningful code):
var GeneralView = Backbone.View.extend({
events: { "click .getNearestCar": "_getNearestCar" },
_getNearestCar: function () {
$.getJson('/get/nearest/car', function (data) {
// suppose the data.id is the id of the nearest car
var nearestCar = window.Cars.get(data.id)
// do what you plase with nearestCar...
});
}
});
HI my basic model which fetches data from server is working perfect. I want to implement a search feature. When user enters any data the request goes to browser and desired model is returned.
var Book = Backbone.Model.extend({
urlRoot: '/books'
});
render: function(options) {
books = new Book({id:options.name});
books.fetch();
}
where
name = "search/"+dynamic_data;
Request URL that is being formed when i pass --> 'life' in variable dynamic_data
http://host/path/search%2Flife
Request URL that i want
http://host/path/search/life
How can I encode/escape my string to achieve the desired result. I have tried escape(), encodeURI(), encodeURIComponents
A workaround to solve this is create one more model with urlRoot as /books/search and pass just name . I don't think this is correct. Should I use this ?
According to your additionnal precisions stating that life is actually a book name...
It looks like Backbone is better integrated with RESTful API's. In REST, your urls should not contain verbs and to search books, you would do a GET /books/?name=life.
In that case, you would only have to define a Backbone.Collection like:
var BooksCollection = Backbone.Collection.extend({
model: Book,
url: '/books'
});
The to fetch books:
var books = new BooksCollection();
books.fetch({data : {name: 'life'}}); //GET /books/?name=life
If you really want your search operation to target /search/:name, you will have to check the Backbone.Collection api, but I think you will want to look at http://backbonejs.org/#Sync
You could override your collection's sync method to something like:
Backbone.Collection.extend({
...
sync: function (method, model, options) {
//for read operations, call the search url
if (method === 'read') {
options.url = '/search/' + options.data.name;
delete options.data.name;
}
//call the default sync implementation
return Backbone.Collection.prototype.sync.apply(this, arguments);
}
});
In this cased calling books.fetch({data : {name: 'life'}}); will result in GET /books/life.
Here's a fiddle that shows the example.
this would work:
books = new Book({id:options.name}, {url: options.name));
decodeURIComponent() will decode http://host/path/search%2Flife to http://host/path/search/life.
I have the following Model:
window.MyModel = Backbone.Model.extend({
initialize: function(props){
this.url = props.url;
}
parse: function(){
// #override- parsing data fetched from URL
}
});
// instantiate
var mod = new MyModel({url: 'some/url/here'});
I use this global variable 'mod' to fetch some data into this model from backend.
// fetch
mod.fetch({
success: function(){ ...},
error: ...
});
All above works well....
My Issue: I want to reuse this model by changing resetting the url and call fetch but it does not update the url somehow. I have tried the following:
mod.fetch({
data: {url:'/some/other/url'},
postData: true,
success: function(){ //process data},
error: ...
});
mod.set({url: '/some/other/url'});
// called fetch() without data: and postData: attributes as mentioned in previous
How do I set the url for my model so that I could call fetch() and it fetches data from updated url? Am I missing something. Thanks for any pointers..
UPDATE 1: Basically, I am unable to get updated values if I did
model.set({url: 'new value'});
followed by
model.fetch();
'model' is a global variable. Creating a fresh instance of 'model' works:
model = new Model({url:'/some/other/url'});
model.fetch();
however, works as required. Does this mean that a model instance is permanently attached to a url and it cannot be reset?
ANSWER TO MY QUESTION in UPDATE 1 Model instance is not permanently attached to a url. It can be reset dynamically. Please read through #tkone's thorough explanation and then #fguillens' solution for a better understanding.
After have understood the #tkone 's explanation...
If you still want to have a dynamic Model.url you always can delay its construction to run time, try this:
window.MyModel = Backbone.Model.extend({
url: function(){
return this.instanceUrl;
},
initialize: function(props){
this.instanceUrl = props.url;
}
}
Well the answer here is that you want to do:
mod.url = '/some/other/url'
The URL isn't part of the instance of the model itself, but rather an attribute of the MyModel object that you're creating your model instance from. Therefore, you'd just set it like it was an normal JavaScript object property. set is used only when the data you're setting (or conversely getting with get) is actually an attribute of the data you want to send/receive from the server.
But why you're changing the URL is the question we should be asking. The idea behind Backbone's model/collection system is that you speak to a REST endpoint and each model has a corresponding endpoint.
Like you've got a blog and that blog has an "entry" object which is available at:
/rest/entry/
And you've got a Backbone model for Entry:
Entry = Backbone.Model.extend({urlBase: '/rest/entry'});
Now when you save or fetch Backbone knows how this works.
So like you're making a new model:
e = new Entry();
e.set({title: "my blog rulez", body: "this is the best blog evar!!!!1!!"});
e.save();
This would then make Backbone do an HTTP POST request to /rest/entry with the body:
{
"title": "my blog rulez",
"body": "this is the best blog evar!!!!1!!"
}
(When you do your mod.set({url: '/some/other/url'}); you're actually adding a field called url to the dataset, so the server would send "url": "/some/other/url" as part of that JSON POST body above:
{
"title": "my blog rulez",
"body": "this is the best blog evar!!!!1!!",
"url": "/some/other/url"
}
The server would then respond with an HTTP 200 (or 201) response with the same model, only with, like, say, and ID attached:
{
"id": 1,
"title": "my blog rulez",
"body": "this is the best blog evar!!!!1!!"
}
And that's not what you're looking for, right?)
Now you've got this model and it's got an ID. This means if you change it:
e.set('title', 'my blog is actually just ok');
e.save()
Backbone now makes an HTTP PUT request on /rest/entry/1 to update the resource on the server.
The server sees that you're talking about ID 1 on the /rest/entry/ endpoint, so knows to update an existing record (and send back an HTTP 200).
TL;DR
Don't change the URL, Backbone will. Make a new model for a new piece of data.
model.urlRoot = "/your/url"
OR
model.urlRoot = function(){ return "/your/url"; }
OR
model.url = "/your/url"
OR
model.url = function(){ return "/your/url"; }
Default 'url' property of a Backbone.Model object is as below. Backbone.js doc says:
Default URL for the model's representation on the server -- if you're using Backbone's restful methods, override this to change the endpoint that will be called.
url: function() {
var base = getValue(this, 'urlRoot') || getValue(this.collection, 'url') || urlError();
if (this.isNew()) return base;
return base + (base.charAt(base.length - 1) == '/' ? '' : '/') + encodeURIComponent(this.id);
},
Clearly, It first gets the value of urlRoot, if not available, it will look at the url of the collection to which model belongs. By defining urlRoot instead of url has an advantage of falling back to collection url in case urlRoot is null.
You can set url as option in fetch function, like this:
var mod = new MyModel();
mod.fetch({
url: '/some/other/url',
data: {}
});
I have an API that filters a set of objects based on the ID present in the URL, like so:
http://localhost:8000/api/v1/goal_update/?goal__id=12&format=json
I have a collection that does a GET request on the above URL. Here is the code for the collection:
var GoalUpdateList = Backbone.Collection.extend({
// Reference the Goal Update model
model: GoalUpdate,
// Do HTTP requests on this endpoint
url: function() {
return "http://localhost:8000/api/v1/goal_update/?goal__id=" + this.goal_id + "&format=json";
},
// Set the goal ID that the goal update list corresponds to
initialize: function(goal_id) {
this.goal_id = goal_id;
},
});
I want to pass in the ID when I create a new instance of the collection, so I created a view that has this code:
this.collection = new GoalUpdateList(this.model.get("id"));
It thinks that I am passing in model parameters, though. I am trying to pass in information that tells the collection what URL to use. So it runs the ID through a validate function and messes up the rest of the backbone code.
Backbone's collections expect model data as the first parameter, as you've already noted. But you can specify a second parameter as an object literal, like other Backbone objects. Just pass null or undefined as the first parameter, and then in your collection initialize method, get the options as the second parameter.
GoalUpdateList = Backbone.Collection.extend({
initialize: function(data, options){
this.goal_id = options.goal_id;
}
});
new GoalUpdateList(null, model.get("goal_id"));
I have a collection which holds some of the users. Some information that is needed is how many total there are, how many pages, etc. How do I pass these back to the client? Or do they have to come from a separate view in which case I will need more than one ajax call? I'd like to have the collection fetch() and also receive some of this "meta data". What's a good way for handling this?
Generally, you need to handle this in the collection class' parse method. Its responsibility is to take the response and return back an array of model attributes. However, you could do more than that if you wished if you didn't mind the parse method having this additional responsibility.
UserList = Backbone.Collection.extend({
model: User,
url: '/users',
parse: function(data) {
if (!data) {
this.registered_users = 0;
return [];
}
this.registered_users = data.registered_users;
var users = _(data.users).map(
function(user_data) {
var user = {};
user['name'] = user_data.name;
return user;
}
);
return users;
}
});
So in the trivial example above, presume the server returns a response which contains a count of registered users and and an array of user attributes. You would both parse through and return the user attributes and you would pick off the registered user count and just set it as a variable on the model.
The parse method would get called as part of a fetch. So no need to modify the fetch, just use the built-in hook method that you have.
Purists would say that you are giving the parse method a secondary responsibility which might surprise some people (e.g. returning something and modifying model state). However, I think this is okay.
One way to do this is to override the Collection::fetch() method so that it parses this metadata out of the response. You could have your backend return a response like this:
{
"collection": [
{ ... model 1 ... },
{ ... model 2 ... },
...
],
"total_rows": 98765,
"pages": 43
}
In your fetch method which overrides the original Backbone.Collection::fetch() method, you can handle each property of the object separately. Here's you could do the override with a slightly modified fetch method:
_.extend(Backbone.Collection.prototype, {
fetch : function(options) {
options || (options = {});
var collection = this;
var success = options.success;
options.success = function(resp) {
// Capture metadata
if (resp.total_rows) collection.total_rows = resp.total_rows;
if (resp.pages) collection.pages = resp.pages;
// Capture actual model data
collection[options.add ? 'add' : 'refresh'](
collection.parse(resp.collection), options);
// Call success callback if necessary
if (success) success(collection, resp);
};
options.error = wrapError(options.error, collection, options);
(this.sync || Backbone.sync).call(this, 'read', this, options);
return this;
});
Note that this approach using _.extend will affect all your classes which extend Backbone.Collection.
This way, you don't have to make 2 separate calls to the backend.
I would bootstrap the information at pagecreation. Write the information into the html document when the server creates the site. Like that you don't have to have an ajax call at all. I do that with the whole collection in ordner not to first load the page and then wait for the ajax call to return the information needed.
Code example with Python:
Line 64: https://github.com/ichbinadrian/maps/blob/master/python/main.py <- from here
Line 43: https://github.com/ichbinadrian/maps/blob/master/templates/index.html <- into here