i'm very confuse about how ember controller works.
I'm starting with ember and ember-cli now, and i would like to understand more about how controller works.
If i have an nested route called new, inside a events resource, i should i have:
models/event
routes/events/new
templates/events/new
What about controllers?? I just work one simple controller, or should i use controllers/events/new too?
There isn't any generator command that will create every resource for me? I need call one by one?
Thanks.
What about controllers?? I just work one simple controller, or should i use controllers/events/new too?
This mainly depends on what is your controller needs to do. If it's only the essential stuff the controller does anyways, Ember will create that controller under the hood for you and automatically bubble actions up to its parent controller.
No better place than Ember guides to read what a controller is used for:
The simplest definition is:
Controllers allow you to decorate your models with display logic.
This means that you basically use them as the main communication layer between your route and your template. Essentially, you model comes from your route, through your controller and into your template. Actions happening in the template go up to the controller and then to the route. Therefore, controller is essentially the middle layer where you user your model (and other data) to control what is shown to the user, control what a user can do, control where can they navigate etc.
However, be aware of the plan for the future:
Controllers are very much like components, so much so that in future versions of Ember, controllers will be replaced entirely with components. At the moment, components cannot be routed to, but when this changes, it will be recommended to replace all controllers with components.
This means, that right now, controller responsibility is limited to two things:
Maintaining application state based on the current route
Handling or bubbling user actions that pass through the controller layer when moving from a component to a route.
All actions triggered on a template are first looked up on the controller, if it is not handled or bubbled (by return true) in the controller, they are looked up on the route.
Therefore, controllers for your /events or events/new routes aren't necessary at all, only if you want to handle things happening on those routes right away (in a smaller scope) instead of allowing everything to bubble up to the ApplicationController.
There isn't any generator command that will create every resource for me? I need call one by one?
Yes. Since, if you don't specifically create a controller, Ember just generates one for you behind the scenes. You need to specify where you want to handle things yourself.
You should visit the link I gave above (or here it is again) to the Ember guides that have many more examples in much more detail.
I've got a big complicated SPA that I'm coding in angular. In it, I need to keep track of actual Model data - operationalized as "stuff that I get from and send to the backend API server". I also have viewstate data - "stuff I keep track of, but don't send to the API server". Model data is stuff like user nicknames or forum post bodies, whereas viewstate data is "this particular UI element is expanded" - it's application state basically.
What I'm wondering is: is there a best-practices approach to this? In my more complicated controllers, I've got an ng-repeat of elements, each element has expando-UI elements. The temptation is to put those expandos inside an ng-if and attach a .showing variable to the object. For example one could imagine this kind of text: ng-repeat="user in users", ng-click="user.showing = !user.showing", ng-if="user.showing" in a few divs. This is really handy because all the information we need about the view state of a repeated item is right there on the repeat.
This also smells terrible - it potentially overwrites fields that were fetched from the API server, and since I cache data models to save on API roundtrips (and handle realtime updates), it also means that view state gets preserved when the user navigates away and then back to the same place in the SPA, or that the view state would be linked in the event the same data is displayed twice on the screen (say, the same profile is showing in three places on the screen as three replies to a post).
I've got some ideas about what to do here. I could encapsulate all the view state variables in their own place in the controller, which has the side-effect of making ng-repeats a lot harder to pull off (you have to look up the view state variable using the $index property probably).
I could encapsulate this one problem in a directive, calling ng-repeat on the directive, which would itself have isolate scope and only has one set of state variables to track (so it therefore doesn't need to worry about tracking complex view state).
I could do something else entirely that the SO community suggests.
I'm leaning toward the directive route. This seems like the Angular Way of doing things. Each UI element doesn't really need to share its state outside of itself, I am currently only really doing this because my initial web mockups were big HTML templates that I got and then attached ng-repeat directives to. I can break the Post, Comment, Author, and so on elements into directives, then they just keep their state on their own.
Yeah, for what it's worth, I ended up breaking everything into directives. Basically, any item inside an ng-repeat that needs to track view state gets its own directive (and therefore its own isolate scope). I also got into the habit of stashing view-related variables on scope.view, so scope.view.showingExpandedReply = true, or whatever. That way I didn't have to pollute the data model with view state information.
when i tell my angularjs app to navigate backwards
$window.history.back();
i see that the previous view's controller is being reused. is there a way to force angularjs to instantiate a new controller?
i am using a ngView element on the page and populating it with templates. perhaps there is a way to dictate to the router that a new controller should be instantiated each time.
(why is stackoverflow insisting on more words before i can submit my questions?....)
I think you should be investigating the $templateCache. I believe in many cases, Angular does instantiate a "new" controller on this event, but your template cache injects the data/state of the view when you use the history service.
Really, it all depends on scope... if your forward progress (app interaction) keeps your state and view within or underneath (as a child of) the same scope, the controller will never be destroyed, however if you leave the scope, it should clean up. (this is actually javascript, and Angular wraps that behavior with $scope). The $templateCache either way will rebuild the state, including data models within your view's assigned controller.
You would have to go about this by intercepting the history event taken, search the $cacheFactory or $templateCache for the key/value pair matching the view in question, then run:
$templateCache.remove('keystring');
prior to allowing the history event to execute. via the $cacheFactory, you can use $templateCache.get() to return information about the views you have cached.
Check out:
- http://docs.angularjs.org/api/ng/service/$cacheFactory
When should I be using router actions as opposed to using controller actions? I know they both serve different purposes but not sure why.
Thanks.
No, technically they serve the same purpose, it's more a matter of where you want actions to be handled/scoped.
Actions are bubbled in a very specific fashion. From the dom they hit the associated controller, then that controller's associated route, then up the route tree (defined by the router mapping). http://emberjs.com/guides/templates/actions/#toc_action-bubbling
So if you think the action will never need to be used past the controller (aka you won't ever want to use it from some child route) then the controller is appropriate, if you think maybe a child route will want to trigger the parent's action then inside the route it goes.
I'm building my first Backbone.js app and I'm confused about how much responsibility I'm supposed to give to or hide from my Views.
In my example, I'm building a Rich UI Table (similar to YUI's datagrid) that's dynamically generated from a Collection. In my app I call this an "AppTable". In my understanding of MVC, I would imagine that there'd be some kind of AppTable controller which finds the correct Collection, grabs a "dumb" View and passes to the View whatever information from the Collection it needs to render. In this senario, the View would do little more than take the data provided to it and modify the DOM accordingly, maybe even populating a template or attaching event listeners.
Backbone seems to do away with the idea of having a controller mediate between the View and Collection. Instead a View gets initialized with a reference to a Collection and it is View's responsibility to update itself.
Am I understanding this architecture correctly?
Assuming I do, my question then becomes, what happens when my View needs to do more and more? For example, I want column sorting, drag-and-drop for rows, pagination, searching, table control links (like new, copy, delete row... etc), and more. If we stick with a "smart" View paradigm where the View is connected directly to a Collection, do the above functions become attached to View object?
Thinking through this, I could see the View growing from a simple table wrapper to pretty messy beast with lot of functionality attached to it. So, is the View really a controller in this case?
Your understanding of the architecture is correct. Backbone does not recognize the concept of a "controller" in the traditional MVC sense. (In fact, Backbone used to actually have an object called a Controller, but it has been renamed Router to more accurately describe what it does.)
The functions you list (drag-drop, delete rows, sorting, etc.) would all belong in a View. A view describes what you see and responds to user input. Anything involving an event (a click, a keypress, a submit, etc.) all go inside of a view. But your view should never actually manipulate the data; that should be done by its model. You are correct in thinking that a view acts like a controller, because it packages data and sends it to the model, which will then validate/set/save appropriately. Once those actions have occurred, the view re-renders itself to represent the new version of the data inside the model.
One note of caution: your view should not be too strenuously tied to the DOM. It is Backbone convention to have a top-level DOM element that your view is tied to (e.g., a form or a div) and then deal only with its sub-elements. That is appropriate; in general, things like "remove this link from this div" inside your view are not. If you find your view growing unwieldy, you most likely need to break it into subviews, each with their respective behaviors as components of their whole.
My thoughts on this updated below:
I think Josh gave a good answer, however, in my experience, building a few Backbone apps, even medium-complexity apps do need a separate controller class.
To clarify what I mean about a controller: The functionality between the model (or router) and the view that creates and instantiates the new view class and kills (and unregisters events) on the old one. This functionality might be the same for many views (so a direct one-to-one relationship between views and controllers probably isn't needed) but sometimes one needs to pass in a model or other additional extra values.
Right now, I just have one controller with a few if statements for adding some unique data to certain views for most apps I've built but I'm looking at setting up an architecture where it will check to see if a unique controller exists for that view else it falls back to the standard controller. Nothing special, but should do the job.
Update: After six months of building Backbone apps I realized that routers can be split up and extended just like views. (duh?)
Right off the bat, I knew to make a base view of functionality I know that all my views would need. Similarly, I would make base views for each section, like "profile" pages or "inbox" pages that I know would all use the same functionality. This wasn't so clear to me in the beginning with routers, but the previous name of "Controller" hinted at this.
Most people (as in every example of Backbone I've ever seen on the web) just use one monolithic router instantiation to handle all routes but you can actually have 1-to-1 parity of routers to views, or in my case, a base router for checking user auth and such and then one for each major section. That way if you need to pass in certain models or collections to a router on page load, you don't need to add code to one monolithic router, but instead pull up the unique router for that view. I find this is currently better than creating a separate controller class. The base router can be in charge of last instantiated view, etc, so you can kill the last view before instantiating the new one.
TLDR: Use multiple Routers as controllers. I believe that's what they were meant for and it works well.
I've struggled with the same semantic issues when trying to map out a single-page app. In the end I decided that Backbone is using the wrong name.
When you look at a Backbone app in the browser, the View is not actually a view at all, its el member is the view. Backbone.View is either a view controller or, probably more correctly, a presenter.
Some supporting evidence:
you never see a Backbone.View on the screen, its always the el or $el that is applied to the DOM
a Backbone.View does not receive user input, the DOM element receives input and the events are delegated via the events hash of the "view"
a BackBone.View manages model or collection changes and translates these changes to dumb-view (DOM) elements, then applies them to the actual view, e.g. this.$el.append('<p>Cats!')
I think Backbone.Presenter would be a better name, but I can also see the historical issues with there being a former Backbone.Controller and the amount of work renaming introduces.
I have settled on the following structure for my latest project:
an app controller, extended from Backbone.View, tied to the body element
several model collections to cache data retrieved from the server
a Backbone.Router that translates route changes into Backbone events and triggers them on itself
many app controller methods that handle the router events the app controller listens to
an app controller method prepares any needed models, then initiates a presenter (extended from Backbone.View) and attaches it to the body element
All these parts are initiated and owned by the app controller. The presenters do not know why or where they are on the page and only care for their own DOM elements and the changes they receive from this.model.
Have a look at this part of backbone documentation
http://documentcloud.github.com/backbone/#FAQ-tim-toady
References between Models and Views can be handled several ways. Some
people like to have direct pointers, where views correspond 1:1 with
models (model.view and view.model). Others prefer to have intermediate
"controller" objects that orchestrate the creation and organization of
views into a hierarchy. Others still prefer the evented approach, and
always fire events instead of calling methods directly. All of these
styles work well.
So, backbone does not take that decision for you.
I have a very similar use case (table grid with pagination, ordering, live filtering, and forms with client-side validation, master-details relations, etc.)
In my case, I first started with a Router behaving just like a controller, and quite quickly my code got a bit messy.
So I completely removed Routers (I'll add them back later, but just as an addition) and created my own controller (that in fact works as a presenter). It's just a javascript class, with Backbone.extend backed in to handle inheritance.
The idea is that the view recieves all the data it needs to display itself (model, collection, and the el in which it should be parsed), set up listener on dom events, and then executes controller methods. It never directly modifies the data nor it interacts with other views, it tells the controller to do it.
A view can have subviews, and in that case the subview only interacts with the parent view, or directly with the controller.
So far now it seems to work, but anyway things are not so simple as I expected them to be...
I hope to publish it in the next few days.
A different perspective from the other answers here is that, just because you are using the Backbone framework, that doesn't mean that your entire codebase must be wrapped in Backbone classes.
Personally, my controller is an amalgamation of "raw" Javascript and Backbone routes, and I never use Views for control logic at all. IMHO views are for ... well, view logic, and specifically for wrapping elements. If you're using a view for anything that doesn't directly connect to an HTML element you are (again, IMHO) doing something wrong.
Backbone is awesome, but that doesn't mean that it's a silver bullet that can be applied to everything.