I'm using Backbone and I have the following model and collection
App.Models.Person = Backbone.Model.extend({
});
App.Collections.People = Backbone.Collection.extend({
model: App.Models.Person,
url: 'api/people',
});
However what I'm struggling on is the best way to render this collection. Here's how I've done it so far which works but doesn't seem to be the most elegant solution
App.Views.PeopleView = Backbone.View.extend({
el: $(".people"),
initialize: function () {
this.collection = new App.Collections.People();
//This seems like a bad way to do it?
var that = this;
this.collection.fetch({success: function(){
that.render();
}});
},
render: function () {
var that = this;
_.each(this.collection.models, function (item) {
that.renderPerson(item);
}, this);
},
I'm fairly new to Backbone but have to assign this to a different variable to I use it inside of the success function just seems like a bad way of doing things? Any help on best practices would be appreciated.
Backbone allows you to register for events that you can react to. When the collection is synchronized with the server, it will always fire the sync event. You can choose to listen for that event and call any given method. For instance ...
initialize: function () {
this.collection = new App.Collections.People();
this.listenTo(this.collection, "sync", this.render);
// Fetch the initial state of the collection
this.collection.fetch();
}
... will set up your collection so that it would always call this.render() whenever sync occurs.
The docs on Backbone Events are succinct but pretty good. Keep in mind a few things:
The method you use to register event listeners (i.e. listenTo or on) changes how you provide the context of the called function. listenTo, for instance, will use the current context automatically; on will not. This piece of the docs explains it pretty well.
If you need to remove a view, you will need to disconnect event listeners. The easiest way to do that is to use listenTo to connect them in the first place; then when destroying the view you can just call view.stopListening().
For rendering, there are a lots of suggestions for how to do it. Generally having a view to render each individual model is one way. You can also use Backbone.Collection#each to iterate over the models and control the scope of the iterating function. For instance:
render: function() {
this.collection.each(function(model) {
var view = new App.Collections.PersonView({ model: model });
view.render();
this.$el.append(view.$el);
}, this);
}
Note the second argument to .each specifies the scope of the iterator. (Again, have a look at the docs on controlling scope. If you'd rather have a framework help out with the rendering, check out Marionette's CollectionView and ItemView.
If your view is supposed to just render the collection you can send the collection to temnplate and iterate through in template, otherwise you can create another subView for that purpose or send the individual models of the collection to another subview and append to the container, hope it was helpful.
Related
I'm developing a webapplication with Resthub, so there is a backbone.js stack at the front-side. I need to call a method, everytime a new view (also all sorts of subviews) is rendered, to add some Twitter-Bootstrap specific stuff (help-popovers, kind of quick help, which get their options from a global json file, so the help-texts are easier to maintain).
As far as I know there isn't a backbone-built-in event which is fired every time a view is rendered.
So my question is: What is the easiest way to extend all views, so that they fire an event when the render method is (implicitly or explicitly) called. I want to extend all my views cause I don't want to trigger this event manually in all views I have, because it's error-prone and all developers has to remember that they've to trigger that event.
If you want to do something(fire an event or anything else) for all cases when the render method is called, the most straight forward way might be to update the render method in your copy of Backbone's source code (assuming you want the behavior across the project).
By default the render method just returns 'this'
render: function() {
return this;
},
If there is something you always want to do before render, you can add it within the render method
render: function() {
//add your extra code/call
return this;
},
Alternatively you can also override the prototype of Backbone.View function and update/create your own version(s) something like
_.extend(Backbone.View.prototype, Backbone.Events, {
render: function() {
console.log('This is a test');
return this;
}
});
var testView = Backbone.View.extend({
});
var testview = new testView();
testview.render(); //displays This is a test
//any view rendered will now have the console log
Taking this a step further, you can add your own version of render, calling it say 'myrender' and/or add your own event(s) say 'myevent' which can then be called before/after you call render/myrender
_.extend(Backbone.View.prototype, Backbone.Events, {
render: function() {
//console.log('This is a test');
this.mynewevent();
return this;
},
myrender: function() {
console.log('Pre-render work');
this.render();
},
mynewevent: function() {
console.log('New Event work');
}
});
var testView = Backbone.View.extend({
});
var testview = new testView();
//testview.render();
testview.myrender();
Underscore's extend is being used here and since Backbone has a dependency on Underscore, if you are using Backbone, Underscore should be available for you as well.
How do you call multiple models in a single view
Usual case is that you create a backbone model
var myModel = Backbone.Model.extend({ url:"api/authentication"});
and then assign it to a view, making it the default model of a certain view
var LoginView = Backbone.View.extend({
model: new myModel(),
initialize: function(){
_.bindAll(this, 'render', 'render_thread_summary', 'on_submit', 'on_thread_created', 'on_error');
this.model.bind('reset', this.render);
this.model.bind('change', this.render);
this.model.bind('add', this.render_thread_summary);
},
...
});
But I have many methods in a single view that calls different models. Currently I just create an instance of a model inside an event method.
The other solution that I'm thinking would be like this
initialize: function(){
_.bindAll(this, 'render', 'render_thread_summary', 'on_submit', 'on_thread_created', 'on_error');
new.model1().bind('reset', this.render);
new.model2().bind('change', this.render);
new.model3().bind('add', this.render_thread_summary);
},
But are these good practices? What else are the other way to do this. Thanks.
UPDATE
In response to Peter, here's my actual code
var userRegModel = Backbone.Model.extend({url: fn_helper.restDomain()+'user/reg'});
var userResendActivationModel = Backbone.Model.extend({url: fn_helper.restDomain()+'user/token/activation/new'});
var userResetPassModel1 = Backbone.Model.extend({url: fn_helper.restDomain()+'user/pwdreset/token/new'});
var userResetPassModel2 = Backbone.Model.extend({url: fn_helper.restDomain()+'user/pwdreset/change'});
var userLoginModel = Backbone.Model.extend({url: fn_helper.restDomain()+'user/login'});
_view: Backbone.View.extend({
el: 'div#main-container',
initialize: function(){},
events: {
'click #user-signup': 'signupUserFn', //userRegModel
'click a#activation-resend': 'resendActivationFn',//userResendActivationModel
'click #reset-password-submit1': 'execResetPasswordFn', //userResetPassModel1
'click #reset-password-submit2': 'execResetPasswordFn', //userResetPassModel2
Each models declared above corresponds to different methods declared in events
Normally model instances should be passed to views in the options argument to the initialize method.
Generally models represent data that either is currently or will eventually be stored in database somewhere. Now, sometimes you want to create a model just for managing ephemeral browser state, which is fine, but the common case is that most read/edit/delete views don't create models unless that's their primary purpose like a "Post New Comment" form. So normally if your view has to show some models, allow them maybe to be updated and saved, they should come into the view in the options argument to the initialize function.
However, if your view really needs so many models and nothing else in your system cares about them, just create them during initialize and store them directly as properties on this (your view instance) and off you go.
If you post a more complete code sample, we can give specific recommendations, but as it is it looks like if you have a LoginView and you need more than 1 model for it, you might be off in the weeds design-wise.
Part Deux
OK, so it looks like you think every API endpoint needs a model. Just implement those as methods on a single model class that use Backbone.sync with the appropriate url option.
var Model = Backbone.Model.extend({
resendActivation: function () {
return Backbone.sync.call('update', this, {url: fn_helper.restDomain()+ 'user/token/activation/new'});
}
});
You may have to do some manual triggering of events and I'm not sure what your API returns, but fundamentally these are all dealing with a single user record and can be handled by a single model.
Misc unrelated tips:
_.bindAll(this); //don't bother listing methods out
this.model.on('reset change', this.render); //bind multiple events at once
JavaScript by vast majority convention use camelCase not lower_with_underscores
In my simple project I have 2 views - a line item view (Brand) and App. I have attached function that allows selecting multiple items:
var BrandView = Backbone.View.extend({
...some code...
toggle_select: function() {
this.model.selected = !this.model.selected;
if(this.model.selected) $(this.el).addClass('selected');
else $(this.el).removeClass('selected');
return this;
}
});
var AppView = Backbone.View.extend({
...some code...
delete_selected: function() {
_.each(Brands.selected(), function(model){
model.delete_selected();
});
return false;
},
});
Thing is, I want to know how many items are selected. In this setup selecting is NOT affecting the model and thus not firing any events. And from MVC concept I understand that views should not be directly talking to other views. So how can AppView know that something is being selected in BrandViews?
And more specifically, I AppView to know how many items were selected, so if more than 1 is selected, I show a menu for multiple selection.
You might want to have a read of this discussion of Backbone pub/sub events:
http://lostechies.com/derickbailey/2011/07/19/references-routing-and-the-event-aggregator-coordinating-views-in-backbone-js/
I like to add it in as a global event mechanism:
Backbone.pubSub = _.extend({}, Backbone.Events);
Then in one view you can trigger an event:
Backbone.pubSub.trigger('my-event', payload);
And in another you can listen:
Backbone.pubSub.on('my-event', this.onMyEvent, this);
I use what Addy Osmani calls the mediator pattern http://addyosmani.com/largescalejavascript/#mediatorpattern. The whole article is well worth a read.
Basically it is an event manager that allows you to subscribe to and publish events. So your AppView would subscript to an event, i.e. 'selected'. Then the BrandView would publish the 'selected' event.
The reason I like this is it allows you to send events between views, without the views being directly bound together.
For Example
var mediator = new Mediator(); //LOOK AT THE LINK FOR IMPLEMENTATION
var BrandView = Backbone.View.extend({
toggle_select: function() {
...
mediator.publish('selected', any, data, you, want);
return this;
}
});
var AppView = Backbone.View.extend({
initialize: function() {
mediator.subscribe('selected', this.delete_selected)
},
delete_selected: function(any, data, you, want) {
... do something ...
},
});
This way your app view doesn't care if it is a BrandView or FooView that publishes the 'selected' event, only that the event occured. As a result, I find it a maintainable way to manage events between parts of you application, not just views.
If you read further about the 'Facade', you can create a nice permissions structure. This would allow you to say only an 'AppView' can subscribe to my 'selected' event. I find this helpful as it makes it very clear where the events are being used.
Ignoring the problems with this that you already mention in your post, you can bind and trigger events to/from the global Backbone.Event object, which will allow anything to talk to anything else. Definitely not the best solution, and if you have views chatting with one another then you should consider refactoring that. But there ya go! Hope this helps.
Here is my case with a similar need: Backbone listenTo seemed like a solution to redirect to login page for timed out or not authenticated requests.
I added event handler to my router and made it listen to the global event such as:
Backbone.Router.extend({
onNotAuthenticated:function(errMsg){
var redirectView = new LoginView();
redirectView.displayMessage(errMsg);
this.loadView(redirectView);
},
initialize:function(){
this.listenTo(Backbone,'auth:not-authenticated',this.onNotAuthenticated);
},
.....
});
and in my jquery ajax error handler:
$(document).ajaxError(
function(event, jqxhr, settings, thrownError){
.......
if(httpErrorHeaderValue==="some-value"){
Backbone.trigger("auth:not-authenticated",errMsg);
}
});
You can use Backbone object as the event bus.
This approach is somewhat cleaner but still relies on Global Backbone object though
var view1 = Backbone.View.extend({
_onEvent : function(){
Backbone.trigger('customEvent');
}
});
var view2 = Backbone.View.extend({
initialize : function(){
Backbone.on('customEvent', this._onCustomEvent, this);
},
_onCustomEvent : function(){
// react to document edit.
}
});
Use the same model objects. AppView could be initialized with a collection, and BrandView initialized with one model from that collection. When attributes of a branch object change, any other code that has a reference to that model can read it.
So lets so you have some brands that you fetch via a collection:
var brands = new Brands([]);
brands.fetch();
Now you make an AppView, and an array of BrandView's for each model.
var appView = new AppView({brands: brands});
var brandViews = brands.map(function(brand) {
return new BrandView({brand: brand});
});
The appView and the brandViews now both have access to the same model objects, so when you change one:
brands.get(0).selected = true;
Then it changes when accessed by the views that reference it as well.
console.log(appView.brands.get(0).selected); // true
console.log(brandViews[0].brand.selected) // true
Same as John has suggested above, the Mediator Pattern works really good in this scenario, as Addy Osmani summing this issue up again in Backbone fundamentals.
Wound up using the Backbone.Mediator plugin which is simple and great, and makes my AMD View modules working together seamlessly =)
I have a backbone app with a view structure that looks like the following - note that I've removed implementations, models, collections, etc. for brevity:
NewsListView = Backbone.View.extend({
el: $('li#newspane'),
// This is what I would like to be able to do
// events: { 'filtered': 'reset' }
initialize: function() {
_.bindAll(this);
},
render: function() {
},
reset: function(){
}
});
FilterView = Backbone.View.extend({
el: $('li.filter'),
initialize: function() {
},
render: function() {
},
toggleFilter: function() {
}
});
AllView = Backbone.View.extend({
initialize: function() {
this.newsListView = new NewsListView();
this.filterView = new FilterView();
}
});
Essentially, whenever the FilterView's toggleFilter() function is called, I would like to fire off an event called filtered or something like that that is then caught by the NewsListView, which then calls its reset() function. Without passing a reference of a NewsListView object to my FilterView, I'm not sure how to send it an event. Any ideas?
You're on the right track. It sounds like what you need is a global event dispatcher. There a decent article and example here: http://www.michikono.com/2012/01/11/adding-a-centralized-event-dispatcher-on-backbone-js/
You might be able to do this using the already available functionality of jquery events and the backbone events property.
For example, instead of doing this from inside your subview:
this.trigger("yourevent", this);
do this instead:
this.$el.trigger("yourevent", this);
Then in any view that is a parent, grandparent, etc of your child view, listen for the event on that view's $el by defining a property on that view's events object:
events:{
"yourevent":"yourhandler"
}
and define the handler on that view as well:
yourhandler:function(subview) {
}
So this way, a view doesn't need to know about what descendant views exist, only the type of event it is interested in. If the view originating the event is destroyed, nothing needs to change on the ancestor view. If the ancestor view is destroyed, Backbone will detach the handlers automatically.
Caveat: I haven't actually tried this out yet, so there may be a gotcha in there somewhere.
You should check out the Backbone.Courier plugin as bubbling events is a perfect use case:
https://github.com/dgbeck/backbone.courier
The easiest way I've found to trigger and listen to events is to just use the Backbone object itself. It already has the events functions mixed in to it, so you can just trigger eg:
Backbone.trigger('view:eventname',{extra_thing:whatever, thing2:whatever2});
then, in any other backbone view in your app, you can listen for this event eg:
Backbone.on('view:eventname', function(passed_obj) {
console.log(passed_obj.extra_thing);
});
I'm not exactly sure what the advantage is in not using the Backbone object as your event handler, and instead creating a separate object to do it, but for quick-and-dirty work, the above works fine. HTH!
NOTE: one disadvantage to this is that every listener will "hear" every single event triggered in this way. Not sure what the big O is on that, but work being careful to not overload your views with lots of this stuff. Again: this is quick and dirty! :)
This problem can be solved using small backbone.js hack. Simply modify Backbone.Events.trigger for passing events to the this.parent
if this.parent != null
So, I came up a with a solution - create an object that extends Backbone.Events, and pass it as a parameter to multiple views. This almost feels like message passing between actors, or something. Anyway - I'm posting this as an answer in case anybody else needs a quick solution, but I'm not going to accept the answer. This feels hacky. I'd still like to see a better solution.
NewsListView = Backbone.View.extend({
el: $('li#newspane'),
// Too bad this doesn't work, it'd be really convenient
// events: { 'filtered': 'reset' }
initialize: function() {
_.bindAll(this);
// but at least this does
this.options.eventProxy.bind('filtered', this.reset);
},
render: function() {},
reset: function() {}
});
FilterView = Backbone.View.extend({
el: $('li.filter'),
initialize: function() {},
render: function() {},
toggleFilter: function() {
this.options.eventProxy.trigger('filtered');
}
});
AllView = Backbone.View.extend({
initialize: function() {
var eventProxy = {};
_.extend(eventProxy, Backbone.Events);
this.newsListView = new NewsListView({eventProxy: eventProxy});
this.filterView = new FilterView({eventProxy: eventProxy});
}
});
In one of the example i picked from SO answers here and many BackBoneJs examples i see that the initialize function knows which view the model is going to be rendered with. I don't know i am kind of biased now, is this a good practice or it depends on type of application being developed.
Example
http://jsfiddle.net/thomas/Yqk5A/
Edited Fiddle
http://jsfiddle.net/Yqk5A/187/
Code Reference
FriendList = Backbone.Collection.extend({
initialize: function(){
this.bind("add", function( model ){
alert("hey");
view.render( model );
})
}
});
Is the above a good practice or below
var friendslist = new FriendList;
var view = new FriendView({el: 'body'});
friendslist.bind("add", function( model ){
alert("hey" + model.get("name"));
view.render( model );
})
in the edited fiddle collection is rendered by a view, and we also can use many more views to render the collection.
I am all for using events,
I myself don't want to move the bind's outside the model, I'd keep them there like the original example
var app = {};
app.evt = _.extend({}, Backbone.Events); // adding a global event aggregator
FriendList = Backbone.Collection.extend({
initialize: function(){
this.bind("add", function( model ){
alert("hey");
app.evt.trigger('addfriend', model);
})
}
});
//further in your code you can bind to that event
app.evt.bind("addfriend", function(model){
var view = new FriendView({el: 'body'});
view.render(model);
});
however, i find the example a bit weird, creating a new view, with body as element, and rendering it with giving a model to the render function. i'd find it more logic if the view is created with a model as attribute, and then rendering the content into the body. but thats another subject all together.
in short, i move creating the view outside, listening to an event being triggered, but the bind on the collection stays in the collection code. i find it more managable to keep all the collection code at the same place.
I don't think the collection should know about the view that is used to render it. I know in my projects, the same collection is render in multiple ways so that approach would deteriorate rapidly.
In general I pass the collection to the view that renders the collection and the view will listen to add/remove/update events of the collection to render the elements. The collection view will have knowledge of the child view.
Check out the following link (3rd blog in a series) and in particular the UpdatingCollectionView. This is the approach that I've found useful.
http://liquidmedia.ca/blog/2011/02/backbone-js-part-3/