detect when a backbone collection has been fetched (Backbone 1.0.0) - backbone.js

There's a new behaviour in the latest version of Backbone (1.0.0 in which the reset event is no longer triggered by default after fetching a Collection.
http://backbonejs.org/#changelog
Renamed Collection's "update" to set, for parallelism with the similar
model.set(), and contrast with reset. It's now the default updating
mechanism after a fetch. If you'd like to continue using "reset", pass
{reset: true}.
The problem is that I want to capture the event when the collection has been finally fetched (pretty common case, indeed!)
I could listen to add, remove and change event, but if the collection is empty I don't know how to catch the event.
So, what would be the new, recommended way to catch when the collection request has finalized, or is it passing a { reset = true } the only way to achieve it???
ps: here's the original question, BTW can't catch Backbone Collection reset event

From Backbone.sync doc,
Whenever a model or collection begins a sync with the server, a
"request" event is emitted. If the request completes successfully
you'll get a "sync" event, and an "error" event if not.
For example,
var C = Backbone.Collection.extend({
url: '/echo/json/'
});
var c = new C();
c.on('sync', function() {
console.log('sync');
});
c.fetch();
And a demo http://jsfiddle.net/nikoshr/GLATm/

We can pass a method as a success handler when we call fetch on collection and as you said you just want to do something when everything[add,remove,update or reset] has happened, you can do inside this success handler.
collection.fetch({
success: function() {
// Do Something
// This is called when all add, remove and update operations have been done
}
});
Note: success handler is always executed irrespective of you have passed reset:true or not. Irrespective of your collection gets empty or not and It will be called at the last step when all the add,remove and update events have occurred.
Let me know if it does not solve your problem.

My own solution is indeed pretty simple. I already have a BaseCollection with added features, so in there I just set as default { reset: true }. The code should be something like this (my own BaseCollection has a lot of stuff that is not pertinent here):
var BaseCollection = Backbone.Collection.extend({
fetch: function(options) {
options = options || {};
options.reset = (options.reset === undefined ? true : options.reset);
// just call super.fetch
return Backbone.Collection.fetch.call(this, options);
};
});

Using promises...
// you could use promises as well
// P.S.: pardon jquery promises :)
var C = Backbone.Collection.extend({
url: '/echo/json/'
});
var c = new C();
// c.fetch() returns jqXHR object that you can listen too
$.when( c.fetch() )
.done(successFn)
.fail(failFn)
.always(alwaysFn);

Related

How to get a Backbone Model attribute after fetch?

I know that a fetch is asynchronous and it needs to use "success" in fetch.
But what if I want to use the data out of the success?
I wanna to get the user ID and to use it in a model "Note".
authedUser.fetch({
success: function(){;
window.uid = authedUser.get("id");
}
But if I try to do this console.log(uid); not in success I get undefined.
You should be able to access updated model from success callback.
Like this:
authedUser.fetch({
success: function(model){;
window.uid = model.get("id");
}
When your new models/collections are registered the "change" event is triggered.
So you can use
MyModel.on("change", function() {
MyModel.get('wtv');
});

Detect when Backbone has finished a model fetch

I can't seem to figure out which event to listen to when fetching data for a model. Usually when I'm doing it for a collection, I listen to the sync event. However, it seems like that doesn't work for models.
So, how do I know when my model is done fetching? Which event does it trigger?
Edit: Here's the beginning part of my view that is using the model:
var HomeContent = BaseView.extend({
initialize: function(options) {
self = this;
this.academyID = this.options.parent.academyID;
this.model = new AcademyModel({academyID: this.academyID});
this.model.on('sync', function() {
console.log('sync');
});
this.model.fetch();
}
fetch returns a jQuery promise. Just use something like:
this.model.fetch().done(function() {
...
}
Another solution is in the docs:
Accepts success and error callbacks in the options hash, which are both passed (model,response, options) as arguments.

Render a view for a model on first load, not on every change

I would like to render a view for a model when the model is first fetched but not on every change.
My setup is as follows:
var m = new $.model.Customer({id: customer});
var v = new $.view.GeneralEditView({el: $("#general"), model: m});
m.fetch();
Then in the view initialize I bind the change event to the render method to render when the model is loaded:
this.model.bind('change', this.render);
The problem is that the view then renders on every change. I'd like to only render after the fetch. Unfortunately I'm not aware of any event that's fired after a fetch for a model other than change.
Is there something like 'reset' for collections that I can bind to?
EDIT:
Perhaps to put it more succinctly, for Backbone models is there a way to distinguish when a model is loaded from the server versus changed locally?
There are a bunch of different ways to approach this (these all assume var view = this; somewhere in your view code):
Call .fetch() with a one-time success callback:
m.fetch({
success: function() {
view.render();
}
});
Bind to change but unbind in the handler:
function handle() {
view.render();
view.model.off('change', handle);
}
this.model.bind('change', handle);
Use _.once to limit handler calls:
this.model.bind('change', _.once(function() {
view.render();
}));
Use a .ready() pattern for your models - example here. I like this option in cases where multiple views need to know when the model is loaded, and when you need to want to be able to write the same code without worrying about whether your model is loaded yet. The downside of this is that it requires you to add a model method like .isFullyLoaded() to test every time; the upside is that using a test function, rather than setting a flag, allows models to be loaded in bulk as part of a collection without having to change your code.
Models
You can make the change event specific to a certain key changing, such as the uniqueId (if you have one):
this.model.bind('change:id', this.render, this);
By default, fetch does not fire any event directly, but indirectly fires the change event once new data is loaded using set
If that is not an option, you can always trigger an event in your fetch function:
initialize: function () {
this.model.bind("fetch", this.update, this);
}
fetch: function () {
// do stuff
this.model.trigger("fetch", this);
}
update: function () {
// your refresh stuff here
}
I may have a general solution from https://github.com/documentcloud/backbone/pull/1468#issuecomment-6766096. I overwrote the sync method on Backbone as follows:
Backbone.Model.prototype.sync = function(method, model, options) {
var succ = options.success;
var customSuccess = function(resp, status, xhr) {
//call original
succ(resp, status, xhr);
model.trigger('synced', model, options);
}
options.success = customSuccess;
Backbone.sync(method, model, options);
}
To save the original success method as I don't want to mess that unless I need to, pass the custom success method. When the custom success method is invoked the custom event is triggered as suggested by #Austin and then the original success method in invoked.

Backbone JS - Model save method and error callback

I am attempting to override a models save method and set an error callback. I am using a mixture of localStorage and server side data so in the event that the app can't connect to the server, I want to save the model to local storage. Here is my model code:
var Project = Backbone.Model.extend({
urlRoot: Settings.urls.projects.project,
save: function(attributes, options){
options || (options = {});
this.set("last_updated", new Date().toISOString(), {silent: true});
options.error = function(){
console.log("Error callback");
}
return this.constructor.__super__.save.apply(this, arguments);
},
As you can see, I am attempting to set options.error within the save method and then call the super method to actually action the save. For some reason it is ignoring the function and the console log statement is not getting called. Anyone have any ideas?
Check this reference:
http://backbonejs.org/#Model-extend
You need to do something like this:
return Backbone.Model.prototype.save.call(this, attributes, options);

Backbone.Model.destroy not triggering success function on success

So, within one of my views, I've got this function:
delete_model: function() {
var answer = confirm("Are you sure you want to delete this element?");
if (answer) {
this.model.destroy({
success: function() {
console.log("delete was a success");
}
});
}
});
When I ping that, the Ajax call goes out, the backend properly deletes the model and returns a 200 header with "OK" as the body...but the success event never fires. Am I missing something? What should I have the backend serve to fire that event?
I just had the same problem. The solution that worked for me was to make sure I return a json model from the server that corresponds to the deleted one.
edit: returning an empty json response will suffice.
Did not work:
delete(model) {
// deleted model from db
return "Model was deleted";
}
This did work:
delete(model) {
// deleted model from db
return model;
}
or:
delete(id) {
// deleted model from db with this id
return new Model {id: id};
}
Had the same problem using Backbone 1.5.3 with Rails. I tried rudena's solution, and it works!
Here's what my controller's delete function looked like initially:
def destroy
#cell = current_user.cells.find(params[:id])
#cell.destroy
render :json => "success"
end
And here's what worked:
def destroy
#cell = current_user.cells.find(params[:id])
#cell.destroy
render :json => #cell
end
That looks good to me, exactly what I have everywhere (except I have function(model) but that shouldn't matter at all) I do know that older versions of backbone didn't use the destroy(options) but instead had destroy(success, failure). Can you make sure you have the latest version.
Had this problem come up with my UI as well. Upon DELETE, the API came back with an empty 200 response.
What's happening is, jQuery expects a json response body, but when the response comes back empty, json parsing fails and the error callback is triggered.
My solution was to override the Model's sync method:
var MyModel = Backbone.Model.extend({
// Fix for empty DELETE response
sync: function(method, model, options) {
if (method === 'delete') {
options.dataType = 'html';
}
Backbone.sync.call(this, method, model, options);
}
});
This works because options is passed to jQuery's ajax call and we're instructing jQuery not to expect json.

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