I'm wondering how people handle the following case in Backbone: usually when a user navigates to the root of your app, a certain set of data is loaded from the backend, processed right away and then displayed in the DOM.
There are links in the app that will navigate you to different sub-sections of it. The router catches the navigation and replaces the current page with whatever page you navigated to, all based on the same data that's already been fetched.
The problem is that the user could bookmark that internal/secondary URL and navigate to it "cold", as in before the data has had a chance to be fetched, without going through the root URL. Is there an idiomatic/conventional way of handling that situation (in the router, I'm assuming)?
One way is, in the various router path-handling functions, to always call a method that will check if there's sufficient data to complete the operation, and if not, fetch it and then proceed?
Backbone won't hit the initial route in your router before you call Backbone.history.start, so you can delay it until you've done the necessary setup. I typically define a start method on my application's main router. Looks something like:
var AppRouter = Backbone.Router.extend({
start: function() {
//init code here
something.fetch({success: function() {
//only call history start after the necessary initial setup is done
Backbone.history.start();
}});
}
});
And then start the application using that method:
window.app = new AppRouter();
window.app.start();
It's good to remember that there is nothing confining you to build your application using only the predefined pieces provided by Backbone. If your startup code is heavy, it may not belong to the router. In such case you should define a helper function to encapsulate the startup logic, and leave the router out of it altogether:
//startup.js
function startup(onComplete) {
//do initialization stuff...
onComplete();
});
//main.js
startup(function() {
Backbone.history.start();
});
Related
Is it possible to close or stop a Backbone Router from listening to its defined routes?
I ask because I have been testing Backbone SubRoute (https://github.com/ModelN/backbone.subroute), setting up an application that has many spaces in which a user could have many subapplications running.
As such, I have defined a a main router, subrouter structure that follows roughy:
MainRouter = Backbone.Router.extend
routes:
"":"root"
"spaces/:id/:module(/*subroute)":"invokeModule"
root: () ->
console.log "root trigger"
invokeModule: (id, module, subroute) ->
that = this
GigaApp.module(module).start({nested_root: "spaces/#{id}/#{module}"})
SubAppRouter = Backbone.SubRoute.extend
routes:
"":"app_home"
app_home: () ->
console.log 'at sub app home'
SubApp.on "start", (options) ->
SubApp.router = new SubAppRouter(options.nested_root)
This general structure works from the first time a sub application is initialized for a space, as the MainRouter starts the SubApp, which initializes its router with the correct nested route. Subsequently, other routes defined in the SubAppRouter also trigger fine.
However, if you navigate to a different space (of different id), and navigate back to the first space, this structure breaks because the SubAppRouter already initialized for that space overrides the MainRouter, and no call the start the SubApp is made from the MainRouter.
So, I'm wondering if there is a way to stop or disable unbind the route triggering of a Backbone router.
As of this moment, the answer is NO
Derick Bailey opened this issue on Backbone's repo suggesting some changes to backbone's structure to support such a change: https://github.com/jashkenas/backbone/pull/1630
There followed a discussion of the merits of such a change, where the following point was made:
To get started -- I'm afraid that I don't understand the premise here. There are a couple axioms of routing that contradict this patch:
Routers exist to match URLs to locations in your application.
The whole point of URLs is that they're always reachable -- once you have a URL, you can go back to it (bookmark it, paste it into a browser) at any point.
I also went over the Backbone source code, and there is no indication that the functionality I am thinking about is possible.
I'm curious why you're not using the AppRouter in Marionette? It should solve your problems regarding dividing routes into smaller AppRoute objects...
Have a look at BackboneRails for some screencasts on building large scale apps. It's not only relevant for devs using rails as backend. It gives a great way to layout your app structure in modules (each with their own App Routes). Highly recommendable.
I have read in several places that calling the Backbone.history.navigate function is considered bad practice.
For example Addy Osmani sais in his book "Developing Backbone.js Applications"
It is also possible for Router.navigate() to trigger the route along
with updating the URL fragment by passing the trigger:true option.
Note: This usage is discouraged...
http://addyosmani.github.io/backbone-fundamentals/#backbone.history
Or Derick Bailey in his blog post even sais:
You shouldn’t be executing the route’s handler from within your application, most of the time.
But I don't really understand the reasoning behind it and what would be a better solution.
In my opinion it is not really bad to call the navigate function with the trigger:true option. The route function could upon calling always check if the considered data is already loaded and show this loaded data instead of doing the whole work all over again...
There seems to be some confusion about what Router#navigate does exactly, I think.
Without any options set it will update the URL to the fragment provided.
E.g. router.navigate('todo/4/edit') will update the URL to #todo/4 AND will create a browser history entry for that URL. No route handlers are run.
However, setting trigger:true will update the URL, but it will also run the handler that was specified for that route (In Addy's example it will call the routers editTodo function) and create a browser history entry.
When passing replace:true the url will be updated, no handler will be called, but it will NOT create a browser history entry.
Then, what I think the answer is:
the reason why the usage of trigger:true is discouraged is simple, navigating from application state to application state to application state requires most of the time different code to be run than when navigating to a specific application state directly.
Let's say you have states A, B and C in your application. But state B builds upon state A and state C builds upon B.
In that case when you navigate from B to C only a specific part of code will need to be executed, while when hitting state C directly will probably execute some state checking and preparation:
has that data been loaded? If not, load it.
is the user logged in? If not redirect.
etc.
Let's take an example: State A (#list) shows a list of songs. State B (#login) is about user authentication and state C (#list/edit) allows for editing of the list of songs.
So, when the user lands on state A the list of songs is loaded and stored in a collection. He clicks on a login-button and is redirected to a login form. He successfully authenticates and is redirected back to the song list, but this time with delete-buttons next to the songs.
He bookmarks the last state (#list/edit).
Now, what needs to happen when the user clicks on the bookmark a few days later?
The application needs to load the songs, needs to verify the user is (still) logged in and react accordingly, stuff that in the state transition flow had already been done in the other states.
Now for a note of my own:
I'd never recommend the above approach in a real application as in the example. You should check whether the collection is loaded when going from B to C and not just assume it already is. Likewise you should check whether the user really is logged in. It's just an example.
IMO the router really is a special kind of view (think about it, it displays application state and translates user input into application state/events) and should always be treated as such. You should never ever rely on the router to transition between states, but rather let the router reflect the state transitions.
I have to disagree with #Stephen's answer here. And the main reason why is because the use of router.navigate({trigger : true}) gives the router responsibility to handle the application's state. It should only reflect application state, not control it.
Also, it is not a View's responsibility to change the hash of the window, this is the router's only job! Don't take it away from it! Good modularity and separation of concerns makes for a scalable and maintainable application.
Forwarding a person to a new section within your application
Backbone is an event driven framework, use events to communicate. There is absolutely no need to call router.navigate({ trigger : true }) since functionality should not be in the router. Here is an example of how I use the router and I think promotes good modularity and separation of concerns.
var Router = Backbone.Router.extend({
initialize: function(app) {
this.app = app;
},
routes: {
'videoLibrary' : function() { this.app.videoLibrary(); }
}
});
var Application = _.extend({}, Backbone.Events, {
initialize: function() {
this.router = new Router( this );
this.listenTo( Backbone, 'video:uploaded', function() {
this.router.navigate('/videoLibrary');
this.videoLibrary();
});
},
videoLibrary: function() {
//do useful stuff
}
});
var uploadView = Backbone.View.extend({
//...
uploadVideo: function() {
$.ajax({
//...
success: function() { Backbone.trigger('video:uploaded'); }
});
}
});
Your view does not need or want to know what to do when the user is done uploading, this is somebody else's responsibility. In this example, the router is just an entry point for the application's functionality, an event generated by the uploadView is another. The router always reflects the application state through hash changes and history but does not implement any functionality.
Testability
By separating concerns, you are enhancing the testability of your application. It's easy to have a spy on Backbone.trigger and make sure the view is working properly. It's less easy to mock a router.
Modules management
Also, if you use some module management like AMD or CommonJS, you will have to pass around the router's instance everywhere in the application in order to call it. Thus having close coupling in your application an this is not something you want.
In my opinion it's considered bad practice because you should imagine a Backbone application not like a Ruby On Rails application but rather like a Desktop application.
When I say RoR, I'm just saying a framework supporting routing in sense that a route brings you to a specific call to the controller to run a specific action (imagine a CRUD operation).
Backbone.history is intended just as a bookmark for the user so he can, for example, save a specific url, and run it again later. In this case he will find the same situation he left before.
When you say:
In my opinion it is not really bad to call the navigate function with
the trigger:true option. The route function could upon calling always
check if the considered data is already loaded and show this loaded
data instead of doing the whole work all over again...
That to me sounds smelly. If you are triggering a route and you are checking for the data to see if you have it, it means that you actually already had them so you should change your view accordingly without loading again the entire DOM with the same data.
That said trigger:true is there so do we have reason use it? In my opinion it is possible to use it if you are completely swapping a view.
Let's say I have an application with two tabs, one allows me to create a single resource, the other one let me see the list of the created resources. In the second tabs you are actually loading a Collection so data is different between the two. In this case I would use trigger:true.
That said I've been using Backbone for 2 weeks so I'm pretty new to this world but to me it sounds reasonable to discourage the use of this option.
It depends on your context.
If you have done something in your current view that might affect the view you are about to navigate to, for example creating for deleting a customer record, then setting trigger to true is the right thing to do.
Think about it. If you delete a customer record don't to want to refresh the list of customers to reflect that deletion?
Since backbone provides two ways of responding to certain events, I was wondering what the general consensus. This is a very common situation - I have a link on a page, i can set up the href on the page to route it so the router can call a function to handle it, like so:
HTML
<a href='#posts/2' class='handleInView'>Item 2</a>
JS
var AppRouter = Backbone.Router.extend({
routes: {
"posts/:id": "getPost"
}
});
or I can respond to the event in the View like so:
var MyView = Backbone.View.extend({
...
events: {
"click .handleInView": "open",
},
...
open: function() {
...
}
});
I know routes provide you with the added benefit of history and direct links, but from a performance standpoint and code layout perspective what is a better approach if I dont care about history.
My routes could be a single place where i can see all of the interactions but it also could get cluttered very quickly.
If you don't care about history or bookmarks, events have fewer side effects (people won't try to bookmark them and they won't interfere with your history) and they're simpler / faster to implement and handle.
Performance-wise, they're slightly faster as well (but really neither method is slow enough to matter at all).
I agree with the comments. Anything that requires deeplinking, bookmarks etc should be handled by using routes. However if you have something like a TabView, or another view that should be inaccessible from a URL, and is nested in another view, then it might make more sense in dealing with that inside of your view code. As for the clutter, you might want to think about reorganizing your routes into separate files. Here are some examples
Backbone general router vs. separate routing files?
Multiple routers vs single router in BackboneJs
In general, routes are used when you are calling a drastic change in the state of your application, or you would like to maintain a browsing history (via backbone.history) so the user can navigate back & forth between states via the browser buttons.
Ideally, you would use both in different circumstances.
I like to think of it in terms of what is changing on my page. If the general page state is the same, but certain elements are changing or updating, I will use events. If the general page state is changing or if I'm loading a different UI Screen, I will use routes.
In many places in my app the following pattern happens:
User clicks some link triggering navigation
Data needs to be fetched to render the view
UI design requires a "loading" spinner to be shown while data is fetched
Once the data is fetched we show the rendered view
I have tried both of the following implementation patterns:
Router handles fetching
Router tells the container view to show the loading spinner
Router loads any collections/models
Router tells the container view to hide the loading spinner
Router passes the collections/models to the view and renders it
View handles fetching
Router just creates and renders the view
The view fetches the collections and models it needs
When the view is first rendered, it just shows the loading spinner since the data is still loading
When the data arrives, the models/collections fire events and the view is bound to those so it re-renders itself, thus hiding the loading spinner and showing the full view
I dislike #1 since the router becomes a gigantic ball of Model/Collection fetching logic and seems to have too much responsibility. #2 seems like a better allocation of responsibilities (router just decides which view to show, view figures out what data it needs to fetch), but it does make the view rendering a little trickier since it's stateful now.
What does the StackOverflow community think? 1, 2, or something else?
This post is pretty old, but we were reviewing it earlier today, so in case anyone else comes across it:
To me, I really see 2 separate questions:
Where should the mechanics of data fetching and the resulting view rendering happen, in the router or a view?
Should views expect already resolved models, or should they respond to models that may still be loading?
A bit of how we handle it mixed with some personal preferences:
Neither, although I'd lean closer to the router. Routers should handle routing, views should handle viewing, and something else should handle the mechanics and workflow of Model/Collection fetching logic. We call that something else a Controller, which the Router basically delegates to.
As Yuri alludes to, 'sometimes' is a reality. I think this is probably a case by case decision, but should ultimately be a contract between a Controller and View, rather than between the Router/View.
I like Yuri's bullet points, with a couple caveats (indented bullets):
The router only knows where to send the user
The outer view only knows what the user should be viewing (given its data)
Assuming the outer view is specific to the inner view's use case and is 'owned' by another view (for clean up)
Otherwise for generic containers(like rendering into a 'main' location), we've found it useful to have a component that manages the views for a certain 'section' on the page - we call it a Renderer
The inner views only know how to show only their little piece of it all (and
can be used elsewhere)
and The render function always shows the right thing as of right now.
In the case of a generic container, it'd ultimately be the responsibility of the Renderer
The main reason for the Renderer is to handle things related to that section, like cleaning up existing views to avoid ghost views, scrolling to the top on render (our MainContentRenderer does that), or showing a spinner in this case.
A psuedo-code-ish example of what that might look like, for:
a generic content target 'main' (if it's use case specific, may be better off with a ComponentView as per Yuri's example, depending on your view lifecycle management strategy)
a model we have to fetch and wait on
a view that accepts an already loaded model
Router:
routes: {
"profile": "showProfile"
},
showProfile: function() {
return new ProfileController().showProfile();
}
ProfileController:
showProfile: function() {
//simple case
var model = new Model();
var deferredView = model.fetch.then(function() {
return new View(model);
};
MainContentRenderer.renderDeferred(deferredView);
}
MainContentRenderer:
var currentView;
renderDeferred: function(deferredView) {
showSpinner();
deferredView.then(function(view) {
this.closeSpinner();
this.closeCurrentView();
this.render(view);
}
},
render: function(view) {
currentView = view;
$('#main-content').html(view.render().el);
}
closeCurrentView: function() {
if (currentView and currentView.close()) {
currentView.close();
}
}
Introducing a Controller also has the added benefit of testability. For example, we have complex rules for performing searches around URL management, picking between a results view and a new search view, and picking between a cached 'last' search result and executing a new search. We have Jasmine tests for the controllers to verify that all that flow logic is correct. It also provides an isolated place to manage these rules.
I tend to use the second option with three views, the container, a loading view, and a content view. That is, the container is instantiated by the router and during each render it looks at what it has on hand to display—sometimes provided by the router, sometimes by itself—and decides what view(s) to instantiate. A simplistic, contrived example:
ContainerView = Backbone.View.extend({
initialize: function (options) {
options.data.bind("reset", this.render, this);
},
render: function () {
var view;
// If the loading view is only shown once, e.g., splashing, then isReady()
// may be better here.
if (this.options.data.isLoading()) {
view = LoadingView;
} else {
view = DataView;
}
this.$("div.content").html(new view().render().el);
}
});
I like this approach because:
The router only knows where to send the user;
The outer view only knows what the user should be viewing (given its data);
The inner views only know how to show only their little piece of it all (and can be used elsewhere); and
The render function always shows the right thing as of right now.
Clarification:
The purpose of the view, in this case, is to understand how what is has to show should best be shown to the user. In this case, a bit of data still loading is best shown with a loading view, while ready data is best shown with a data view. Most real views are actually composing their display with many more views, e.g., depending on the user authorization different action containers.
I'm attempting to use Backbone and it's Router to turn an app into an ajax app, however it currently uses several different methods (helpers) of generating links. Unfortunately, this means manually changing each and every link to use a hashtag is out of the question.
What would be the best method of ensuring every link, form post, redirect, etc. gets parsed as a hashtag URL that can be caught by Backbone's Router? Or, even better, is it possible for the Router to accept "true URL's" from a request? Example: a request to /app/mail/inbox.php is caught by a rule in the Router, and is turned into #/mail/inbox after firing the appropriate method to handle the request.
What would be the best method of ensuring every link, form post, redirect, etc. gets parsed as a hashtag URL that can be caught by Backbone's Router?
I don't think that Backbone.Router is supposed to handle, say, form posts. It's supposed to give your application view state—bookmark-friendly and refreshable URLs [1].
If you want to ‘ajaxify’ forms, then you probably should add a handler for form's submit event and do something like $.ajax() there, preventing the default action.
Regarding plain old links, History.pushState() support has been added to Backbone recently. It means that you can define your routes as /app/*, and don't need to replace old href attributes. However, you'll still need to catch link click events to prevent default action.
For example:
var handle_link_click = function(e) {
path = $(e.target).attr('href');
app.main_router.navigate(path, true); // This.
e.preventDefault();
};
$('a:internal').click(handle_link_click);
Router's navigate() method will do history.pushState() if it's available, falling back to old hashchange. And true as a second argument means that it will fire corresponding handler action.
[1] See also this presentation about Backbone