New to using Backbone and have a very simple application. Basically there are Clients and ClientItems. I have a view to show all Clients and if you click on a Client you get taken to their ClientItems. Going to this ClientItems view should just hide the Clients view and going back to Clients should hide ClientItems. Now, in my render() function for each view, it is going through the collections and dynamically adding stuff to the page. When I go back and forth between the two (using the back button) I don't really need to fully render again as all the data is there in the page, just hidden. Where should this logic go? Right now I have it in the render() function but it feels sloppy, what is the preferred way of handling this?
We are using a global variable App with several common function used across application:
var App = {
initialize : function() {
App.views = {
clientView : new ClientsView(),
clientItemView : new ClientsItemsView()
}
},
showView: function(view){
if(App.views.current != undefined){
$(App.views.current.el).hide();
}
App.views.current = view;
$(App.views.current.el).show();
},
...
}
And then I use this App from other parts of application:
App.showView(App.views.clientView);
IntoTheVoid's solution is good – it's nice to have a single place to hide/show views. But how do you activate the logic?
In my experience, routers are the best place for this. When a route changes and the appropriate function is called, you should update the active, visible view(s).
What if you need multiple views to be visible at once? If you have a primary view that always changes when the route changes, and multiple subsidiary sticky views, you need not worry. But if it's more complex than that, think of creating a ComboView that neatly packages all the relevant views into one containing el node. That way the above logic still works, and your router functions are not littered with logic for managing what views are visible at the moment.
Related
Since I'm not totally sure on which level my issue actually is to be solved best, I'd like to summarise the path I went and the things I tried first:
It's more or less about $el (I think).
As most basic backbone examples state, I started with having the $el defined within its view, like
Invoice.InvoiceView = Backbone.View.extend({
el: $('#container'),
template: ..,
..
});
It didn't feel right, that the view is supposed to know about its parent (=container). The paragraph 'Decouple Views from other DOM elements' written on http://coenraets.org/blog/2012/01/backbone-js-lessons-learned-and-improved-sample-app/) perfectly puts it into words.
Following this article's advice, I switched to passing $el over to the view while calling the render()-method. Example:
$('#container').html( new WineListView({model: app.wineList}).render().el );
So far so good - but now render() gets called, while it maybe shouldn't (yet).
For example the View asynchronously fetches a model in its initialize()-routine. Adding a binding to reset or sync (e.g. like this.model.bind('sync', this.render, this)) makes sure, render() gets definitely called once the model is fetched, however above stated way, render() still might get called while the model isn't fetched yet.
Not nice, but working(TM), I solved that by checking for the model's existence of its primary key:
render: function() {
if(this.model.get('id')) {
...
}
However, what I didn't expect - and if it really isn't documented (at least I didn't find anything about it) I think it really should be - the fetch operation doesn't seem to be atomic. While the primary key ('id') might be already part of the model, the rest might not, yet. So there's no guarantee the model is fetched completely that way. But that whole checking seemed wrong anyway, so I did some research and got pointed to the deferred.done-callback which sounded exactly what I was looking for, so my code morphed into this:
render: render() {
var self = this;
this.model.deferred.done(function() {
self.model.get('..')
};
return this;
}
..
$('#container').html( new WineListView({model: app.wineList}).render().el);
It works! Nice, hu? Ehrm.. not really. It might be nice from the runtime-flow's point of view, but that code is quite cumbersome (to put it mildly..). But I'd even bite that bullet, if there wouldn't be that little, tiny detail, that this code sets (=replaces) the view instantly, but populates it later (due to the deferred).
Imagine you have two (full-page) views, a show and an edit one - and you'd like to instantly switch between the two (e.g. after hitting save in the edit-view it morphs into the show-view. But using above code it sets (=resets) the view immediately and then renders its content, once the deferred fires (as in, once fetching the model is completed).
This could be a short flickering or a long blank transition page. Either way, not cool.
So, I guess my question is: How to implement views, which don't know about their container, involve models which need to be fetched, views which should be rendered on demand (but only once the model is fetched completely), having no need to accept UI/UX trade-offs and - the cherry on the cake - having maintainable code in the end.
First of all, the first method you found is terrible (hard coding selector in view's constructor)
The second: new WineListView({model: app.wineList}).render().el is very common and ok. This requires you to return the reference to view from render method, and everyone seems to follow this, which is unnecessary.
The best method (imo) is to simply attach the views element to the container, like this
$('#container').html(new WineListView({model: app.wineList}).el);
The WineListView doesn't need to know about where it's going to be used, and whatever is initializing WineListView doesn't need to worry about when to render the WineListView view instance:
because the el is a live reference to an HTML Element, the view instance can modify it anytime it wants to, and the changes will reflect wherever it is attached in DOM/ when it gets attached in DOM.
For example,
WineListView = Backbone.View.extend({
initialize: function(){
this.render(); // maybe call it here
this.model.fetch({
success: _.bind(this,function(){
this.render(); // or maybe here
})
});
}
});
Regarding flickering: this hardly has to do anything with rendering or backbone, it's just that you're replacing one element with another and there will be an emptiness for a tiny bit of time even if your new view renders instantly. You should handle this using general techniques like transitions, loaders etc, or avoid having to switch elements (For example convert labels into inputs in the same view, without switching view)
First off, the linked example is outdated. It's using version 0.9.2,
whereas the current version (2016-04-19) is 1.3.3. I recommend
you have look at the change log and note the differences, there are many.
Using the el property is fine. Like everything though, there's a time and place.
It didn't feel right, that the view is supposed to know about its parent (=container). The paragraph 'Decouple Views from other DOM elements' written on http://coenraets.org/blog/2012/01/backbone-js-lessons-learned-and-improved-sample-app/) perfectly puts it into words.
I wouldn't define an el property on every view, but sometimes it makes sense, such as your example. Which is why, I'm assuming, Backbone allows the use of the el property. If you know container is already in the DOM, why not use it?
You have a few options:
The approach outlined in my original answer, a work-around.
fetch the model, and in the success callback, insert the view element into the DOM:
model.fetch({
success:function() {
$('#container').html(new View({model:model}).render().el);
}
});
Another work-around.
Define an el property on the view and fetch the model in the view initialize function. The new content will be rendered in the container element (also the view), when the content/model data is ready, by ready, I mean when the model has finished fetching from the server.
In short,
If you don't want to define an el property, go with number 1.
If you don't want to let the view fetch the model, go with number 2.
If you want to use the el property, go with number 3.
So, I guess my question is: How to implement views, which don't know about their container
In your example, I would use the el property, it's simple a solution with the least amount of code. Not using the el property here, turns into hacky work-arounds that involve more code (complexity) without adding any value (power).
Here's what the code looks like using el:
var Model = Backbone.Model.extend({url:'/model_url'});
var model = new Model();
// set-up a view
var View = Backbone.View.extend({
el:'#container',
template:'model_template',
initialize:function() {
this.model.fetch();
this.listenTo(this.model,'sync',this.render);
},
render:function() {
this.$el.html(this.template(this.model.toJSON()));
return this;
}
});
var view = new View({model:model});
Check out the documentation for el.
Here is an updated working example.
If there is an obvious flicker because, your model takes a noticeable amount of time
to be fetched from the server...maybe you should think about displaying a loading bar/variation thereof
while fetching the model. Otherwise instead of seeing the flicker, it will appear the
application is slow, delayed, or hanging..but in reality - it's waiting to render the next view,
waiting for the model to finish fetching from the server. Sitting on old content, just waiting for
the model to load new data to show new content.
Basically what I'm trying to do, is to find the best way to manage all my views.So all my views get closed and created when it's necessary.. And because of that, I have created a separate manager inside my Backbone.Routerinstance which takes care of all my views as follows.
router.js
AppRouter.prototype.initialize = function () {
.......
var eMgr = _.extend({}, Backbone.Events);
var vMgr = new ViewManager();
vMgr.add(new vTopMenu({eMgr: eMgr}));
vMgr.add(new vTooltip({eMgr: eMgr}));
app_router.on('route:MainMenu', function () {
vMgr.close_all_views(function(){
vMgr.add(new vmainMenu({eMgr: eMgr}));
vMgr.render_all_views();
});
});
app_router.on('route:showMap', function () {
vMgr.close_all_views(function(){
vMgr.add(new vMapMenu());
vMgr.render_all_views();
});
});
...
}
As you can see the TopMenu and Tooltip views are created only once as I don't expect there will be any need to changes their content. And I'd also like to avoid the blank spaces while the views are being loaded...
I'm not sure if this is a good idea though, as all the other views are being closed and re-initiated once I navigate from one route to another.
So the question is, is it a good practice to have these views set up like this? Or should I always re-create the views when any route is triggered?
Some views can be cached if needed. Caching benefits depend on which content are you showing in a view. You have to take into consideration several aspects when making a decision to put a view in the cache:
Large cache size can impact performance, so chose only ones that are used often for caching.
Caching is important for those views, which downloading extra resources.
Be aware, unused views can eat memory resources.
Also, for both cached and uncached cases, you have to remember:
It also can take significant time to re-render view. Those views which are difficult to render can be just hidden, not removed.
Zombie views. Old view should be safely closed, with events unbinding, etc.
I'm trying to figure out following scenario:
Lets say that I have two views: one for viewing items and one for buying them. The catch is that buying view is a sub view for viewing.
For routing I have:
var MyRouter = Backbone.Router.extend({
routes: {
'item/:id': 'viewRoute',
'item/:id/buy': 'buyRoute'
}
});
var router = new MyRouter;
router.on("route:viewRoute", function() {
// initialize main view
App.mainview = new ViewItemView();
});
router.on("route:buyRoute", function() {
// initialize sub view
App.subview = new BuyItemView();
});
Now if user refreshes the page and buyRoute gets triggered but now there is no main view. What would be best solution to handle this?
I am supposed that the problem you are having right now is that you don't want to show some of the stuff inside ViewItem inside BuyView? If so then you should modularized what BuyView and ViewItem have in common into another View then initialize it on both of those routes.
Here is a code example from one of my apps
https://github.com/QuynhNguyen/Team-Collaboration/blob/master/app/scripts/routes/app-router.coffee
As you can see, I modularized out the sidebar since it can be shared among many views. I did that so that it can be reused and won't cause any conflicts.
You could just check for the existence of the main view and create/open it if it doesn't already exist.
I usually create (but don't open) the major views of my app on booting up the app, and then some kind of view manager for opening/closing. For small projects, I just attach my views to a views property of my app object, so that they are all in one place, accessible as views.mainView, views.anotherView, etc.
I also extend Backbone.View with two methods: open and close that not only appends/removes a view to/from the DOM but also sets an isOpen flag on the view.
With this, you can check to see if a needed view is already open, then open it if not, like so:
if (!app.views.mainView.isOpen) {
//
}
An optional addition would be to create a method on your app called clearViews that clears any open views, perhaps with the exception of names of views passed in as a parameter to clearViews. So if you have a navbar view that you don't want to clear out on some routes, you can just call app.clearViews('topNav') and all views except views.topNav will get closed.
check out this gist for the code for all of this: https://gist.github.com/4597606
I have a single page web app with multiple backbone.js views. The views must sometimes communicate with each other. Two examples:
When there are two ways views presenting a collection in different ways simultaneously and a click on an item in one view must be relayed to the other view.
When a user transitions to the next stage of the process and the first view passes data to the second.
To decouple the views as much as possible I currently use custom events to pass the data ($(document).trigger('customEvent', data)). Is there a better way to do this?
One widely used technique is extending the Backbone.Events -object to create your personal global events aggregator.
var vent = {}; // or App.vent depending how you want to do this
_.extend(vent, Backbone.Events);
Depending if you're using requirejs or something else, you might want to separate this into its own module or make it an attribute of your Application object. Now you can trigger and listen to events anywhere in your app.
// View1
vent.trigger('some_event', data1, data2, data3, ...);
// View2
vent.on('some_event', this.reaction_to_some_event);
This also allows you to use the event aggregator to communicate between models, collections, the router etc. Here is Martin Fowler's concept for the event aggregator (not in javascript). And here is a more backboney implementation and reflection on the subject more in the vein of Backbone.Marionette, but most of it is applicable to vanilla Backbone.
Hope this helped!
I agree with #jakee at first part
var vent = {};
_.extend(vent, Backbone.Events);
however, listening a global event with "on" may cause a memory leak and zombie view problem and that also causes multiple action handler calls etc.
Instead of "on", you should use "listenTo" in your view
this.listenTo(vent, "someEvent", yourHandlerFunction);
thus, when you remove your view by view.remove(), this handler will be also removed, because handler is bound to your view.
When triggering your global event, just use
vent.trigger("someEvent",parameters);
jakee's answer suggests a fine approach that I myself have used, but there is another interesting way, and that is to inject a reference to an object into each view instance, with the injected object in turn containing references to as many views as you want to aggregate.
In essence the view-aggregator is a sort of "App" object, and things beside views could be attached, e.g. collections. It does involve extending the view(s) and so might not be to everybody's taste, but on the other hand the extending serves as a simple example for doing so.
I used the code at http://arturadib.com/hello-backbonejs/docs/1.html as the basis for my ListView and then I got the following to work:
define(
['./listView'],
function (ListView) {
var APP = {
VIEWS : {}
}
ListView.instantiator = ListView.extend({
initialize : function() {
this.app = APP;
ListView.prototype.initialize.apply(this, arguments);
}
});
APP.VIEWS.ListView = new ListView.instantiator();
console.log(APP.VIEWS.ListView.app);
}
);
I have an application that has a middle panel that always changes depending on what part of the application the user is looking at. These might be messages, transactions etc.
Then there are 4 'fixed' panels at the 4 corners of the application around the middle panel that are mostly fixed for the lifetime of the application, but contain dynamically updated data and therefore need to be implemented using backbone.js
How do I structure such an application in backbone.js. It seems to defeat the "Do not repeat" rule to implement the intial rendering for all the side panels within every route in the router as I would end up repeating the same rendering code in every route.
How do I structure my code in this instance so that I don't repeat code in multiple places.
JavaScript is like any other code: if you find yourself writing the same lines of code, extract them in to a function. If you find yourself needing to use the same function, extract it (and related functions and data) in to its own object.
So, your router shouldn't be calling your views and models directly. Instead, it should be delegating to other objects that can manipulate your views and objects.
Additionally, since your going to set up the same basic page layout every time the app starts up, you might not want that code in the router. The layout happens whether or not the router fires, and no matter which route is fired. Sometimes it's easier to put the layout code in another object, as well, and have the layout put in place before the router fires up.
MyApplication = {
layout: function(){
var v1 = new View1();
v1.render();
$("something").html(v1.el);
var v2 = new View2();
v2.render();
$("#another").html(v2.el);
},
doSomething: function(value){
// do someething with the value
// render another view, here
var v3 = new View3();
v3.render();
$("#whatever").html(v3.el);
}
}
MyRouter = Backbone.Router.extend({
routes: {
"some/route/:value": "someRoute"
},
someRoute: function(value){
MyApplication.doSomething(value);
}
});
// start it up
MyApplication.layout();
new MyRouter();
Backbone.history.start();
I've written a handful of articles relating to these things, which you might find useful:
http://lostechies.com/derickbailey/2012/02/06/3-stages-of-a-backbone-applications-startup/
http://lostechies.com/derickbailey/2011/08/30/dont-limit-your-backbone-apps-to-backbone-constructs/
http://lostechies.com/derickbailey/2011/12/27/the-responsibilities-of-the-various-pieces-of-backbone-js/
http://lostechies.com/derickbailey/2012/03/22/managing-layouts-and-nested-views-with-backbone-marionette/