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Overlapping Views Manager in Backbone

I have a Backbone + RequireJS application with root views that are rendered upon page load. In addition I have a bunch of views that are opened on top of the root views or on top of each other.
The idea is that each view triggers a change, adding a fragment to the URL. Multiple views can be rendered on top of each other with certain parameters defined by the view that launched them.
How do I achieve a structure that passes required data to the view that is rendered and that browser history stays aware of the changes and switches views accordingly?
In practice for example, if I press the back button, the front most view is removed and the underlying view is activated with all the data that it was initialized with.
EDIT:
What I need:
Router that listens for hash value changes and maintains a stack for views that are rendered
A way to initiate and render a view from inside another view with certain parameters
USE CASE: Every time a user opens a new view on top of an existing view, the router stores the new view in the stack. With a dedicated "close" button or pressing the browser's "back" button the router automatically removes the top view from the stack and the previous view is exposed.
What kind of a structure should I build to achieve this kind of functionality?

How to update parts of a Backbone view?

I'm using Backbone for a webapp in which I fetch a model from an API call and populate a view with that. Within that view, there are a couple things, among which is a textarea and some sort of chat area (which is populated with other views). So far so good.
I now want to call the API again, and if the initial model changed I want to update parts of that view. My problem is now, that I am afraid that if I reload the view, the things that people might have written in the textarea are gone.
I guess I can make a call and update parts of the view using jQuery, but I think that's not really the idea behind Backbone.
So my question is now; how can I use Backbone to update parts of the initial view without reloading the whole view? All tips are welcome?

Typically a view is bound to a model and it represents a part of the DOM.
When you say that the view should update when the model changes, my first thought is that this would be a separate view from the inputbox.
For example, there could be one parent view that is represented as a wrapper element, and multiple subviews that represent different models.
You can still manage events from your parent view, because events will bubble up.
It is important to take into account proper view cleanup when you're working with subviews though. Marionette.js is a library that manages this well.
Alternatively, you can temporarily cache the user input and populate the view back after it's rendered.

Your view needs to listen to model changes. If you render your view you pass your model to the template. And in your initialize function of the view you tell yout view the listen to model changes. See here.
var view = Backbone.View.extend({
initialize: function(){
this.model.on('change', this.render, this);
},
render: function() {
// ...
}
});

Dealing with partial views and javascript

I have set up a partial view to render in an index page. The partial view gets posted using Ajax to the server when a user clicks a sort button. This is so the entire page won't refresh just the partial view table.
The problem is after the first sort, the JavaScript in the index page is no longer effective. I worked around this by putting the js in the partial view itself to persist the events, but this produces js errors to saying 'continue' or 'ignore'.

It is because your newly injected elements ( via ajax) is not aware of the events bounded. So those event bindings are not availabel to them.
You should change your event bindings to use on so that it handles the current elements and future elements (added to DOM dynamically via ajax or so)
for example, if you want to handle the click event for elements with css class someCssClassSelector,
Change
$(".someCssClassSelector").click(function(){
//do something
});
to
$(document).on("click",".someCssClassSelector",function(){
//do something
});

Managing views with complex states

I have a backbone.js app, whose views have multiple states, which differ substantially from each other ("View","Edit", etc). There are at least 2 different templates for every view. This is OK. My problem is with the JS view managing code.
I rely on an initalize-thin-render-thick approach (which, I think is pretty bad), where the render method is where 80%-90% of the logic occurs. When I want to change the state, I simply call the render method with a specific parameter ("view","edit"). On the basis of that, the view decides what to show and what not, to which events to bind, etc.
I think this is bad, because, on one side it puts bottlenecks on the rendering process, on another, it is not proper state machine, which means that I am not carrying about possible callbacks that might have been bound previously. When I receive the view, I simply clean the view and that's it.
I also observed, that I am not using the delegated event system, provided by backbone, which I think is another minus, because I think, it is very well implemented (BTW, does it make sure to unbind callbacks, when a certain DOM element is removed?)
I think I need some serious refactoring. Please, help with some advice, as to what the best approach for a multi-state Backone view would be.

What I tend to do for these cases is to make a toplevel view that manages a subview for each individual state (index, show, edit, etc.). When a user action is invoked, e.g. "edit this user", "delete this user", "save my changes", the active state view signals the router (directly, or through a hyperlink), and the router will tell the toplevel view to update its state.
Continuing the user editor example, let's say that I have a top level view called UserEditorView. It renders a basic container for the user editor (title bars, etc.) and then, by default, instantiates and renders Users.IndexView inside that container.
Users.IndexView renders the list of users. Next to each user is an edit icon, which is a link to "#users/555/edit". So, when the user clicks it, that event goes to the router, which tells UserEditorView, "hey, I want to edit user #555". And then UserEditorView will remove the IndexView (by calling its .remove() method), instantiate Users.EditView for the appropriate user model, and put the EditView into the container.
When the user is done editing the user, she clicks on "Save", and then EditView saves the model. Now we need to get back to the IndexView. EditView calls window.router.navigate('users', { trigger: true }), so the URL gets updated and the router gets invoked. The router then calls .showIndex() on the UserEditorView, and the UserEditorView does the swap back to IndexView from EditView.

On a simple way to manage unloading of events, I've found this article on zombie views quite useful.
Basically, I don't have a toplevel view, but I render all the views using a view handler that takes care of the views for a given container.
To make your renderer thinner, I would recommend using routes. They are easy to setup, and you can have different views for each route. Or, what I'm used to do is just to have different templates. Using a general Backbone.View overwrite:
Backbone.View = Backbone.View.extend({
initialize: function(attrs) {
attrs = attrs || {}
if(!_.isUndefined(attrs.template)) {
this.template = attrs.template;
}
}
});
I've noticed that I reuse views in two ways:
1. edit views differ only in the underlying model and template, but not the associated logic (clicking the submit validates and saves the model)
2. the same view can be reused in several places with different templates (like a list of users as a ranking or you accounts)
With the above extension, I can pass {template: '/my/current/template/} to the view, and it will be rendered as I want. Together with routes, I finally got a flexible, easy to understand and thin setup.

Elegant way to prevent circular events in MVC?

The question, in brief:
In MVC, how do you distinguish between a checkbox click (or a selectbox or listbox change) from a human meaning "Controller, modify the model", and a checkbox click (or a selectbox or listbox change) from the Controller meaning "I'm updating the view because the model has changed"?
The example:
I have a JS app (all one big HTML+JS page; there's a server behind it, and AJAX going on, but it's not important to the example) which has the notion of "Vertices" connected by "Edges". The UI lets you add and remove Vertices on a map, and enable or disable Edges between pairs of Vertices.
There are two ways to disable an Edge from Vertex A to Vertex B:
click on the Edge to make the "Edge Details" window provide you with a "Disable This Edge" button; or
click on Vertex A (or B) to make the "Vertex Details" window provide you with a checklist of nearby Vertices, from which you can uncheck Vertex B (or A).
Here's how this works under the hood in MVC (but see the end of this post for an update, where I correct problems in my understanding):
Model: a list of Vertex objects and a list of Edge objects.
View: a GMaps UI, with markers and polylines, plus checkboxes and buttons and "Vertex Details" and "Edge Details" DIVs.
Controller:
JS functions that update the model when events on the checkboxes and buttons fire; and
JS functions that update the view when events on the models fire.
Here's the specific inelegance:
The user has the Vertex Details Window focused on Vertex A, and the Edge Details Window focused on the Edge from Vertex A to Vertex B.
The user clicks "Disable This Edge" in the Edge Details window.
Controller function 1 gets the click event, and calls disable() on the Edge model object.
The Edge model object fires the "I just got disabled" event.
Controller function 2 receives the "I just got disabled" event, and
redraws the Edge Details Window to say "I'm disabled!" and
unchecks Vertex B in the Vertex Details Window.
Crap! This fires Controller function 1 again, which was listening for UI events that mean an edge was disabled!
So there's an unnecessary re-update of the Model, and re-update of the View. In a more complex view with events that fire events that fire events, this can make for dozens of extraneous updates!
Update: a great answer.
I misunderstood MVC a bit. I don't have just one View, as I described above: I have several Views into several Models. In particular, I have a checkbox-list View of Edges to a particular Node, and a separate, "detailed window-style" View of an Edge.
Furthermore, I shouldn't have one controller function updating all views when the Model changes: each View should modify itself when the Model changes.
So if each View registers for "state updated" events on the Model, and each View updates itself upon receipt of those events, then the answer to my circular events question is simply this:
The checkbox-list View will disable checkbox events for the moment that it is updating the checkboxes after a Model state change.
Now if a user disables an Edge via the Edge Detail window, the Controller updates the Edge Model, the checkbox-list View receives notification of the update, and the checkbox-list View is smart enough to silence checkbox events while changing the status of the appropriate checkbox.
This is much more palatable than my original solution, where one Controller updates ALL Views -- and thus has to know which views need special care and feeding to avoid loops. Instead, only the single View with troublesome UI elements has to deal with the problem.
Thanks to those who answered my question!

Just to recap the MVC model. Views should generally update themselves. Here's how it works: a controller changes the state of the model, the model sends updates to its views, the views pull in new state from the model and update themselves. While controllers and views are generally bundled (i.e. drilling down on data in a graphic representation) they should never interact directly, only through the model. This in general of course.
So the JS functions that update your views are not actually controllers, which is an important distinction. They should be considered part of your view. This might not be helpful to the problem at hand but I thought it merited pointing out.
You can also not delete your model, I assume you mean you're deleting someting from your model, since no views or controllers can actually exist (or be in a functional state) if they're not backed by a model.
Not being a JS code jockey and not having used gmaps I don't really see where the problem is. Does changing the state of a checkbox(checked property) fire the onClick() event? It really shouldn't IMHO but perhaps they implemented it that way, otherwise you could just attach your controller to the onClick() and add some logic to the checkbox (or, this being JS, in a function somewhere) to change the checkbox state. If that's not possible, option 1 and 2 are definitely your best bet.
addition: user interacting with a view
So what happens when a user wants to interact with a view? Frequently a widget will include both a view and the controller. A checkbox has a view (you can see if it's checked or not) and also a controller (you can click it). When you click the checkbox, in principle the following should happen:
checkbox controller receives the event
checkbox controller changes the state for the value this checkbox represents in the model
model updates listeners (including the checkbox)
checkbox updates its look to reflect that that value has changed
The first step, how the controller receives the event is somewhat language dependent, but in OOP languages it's likely a listener object attached to user interface events on this particular widget which either is the controller or notifies the controller of the user interaction.

This is a tough one. If I understand correctly, the problem results because you've exposed a click handler on your model, and the model's click event is caught by the controller. The controller updates the view, which in turn toggles the same event.
From my point of view, I would consider it inappropriate for the Controller to attach itself to the Edge's Click event, because it exposes too much detail about how the Edge is implemented and used. Controller does not care about how the Edge is used or any other implementation details.
In fact, canonical MVC style doesn't require the Controller to hook onto any Model events at all, generally because the Model's state is not mutated by the View or any other Controllers. Its not necessary for the Model to notify the Controller that it's been changed.
To fix your problem, you should define View's interface to have a single method, such as ToggleEdge:
public interface GraphView
{
event Action ToggleEdge;
}
Its tempting to want to create two methods, EdgeClicked and CheckboxClicked, but insisting on two independent methods like that violates the principle of encapsulation. It exposes too many implementation details to your Controller or anyone else who wants to hook onto those events. Remember, the Controller only cares that the View's state changed, it doesn't care how it changed.
When you implement the View interface onto your user interface, you should take care to ensure that the ToggleEdge event is invoked from one location. You can do this by hooking onto the Edge.Clicked event in your View and using it to toggle your checkbox; this makes your checkbox responsible for raising the Toggle vent up to the controller:
public class UI : UserControl, GraphView
{
public event Action ToggleEdge;
void OnToggleEdge(Edge edge)
{
if (ToggleEdge != null)
ToggleEdge(edge);
}
protected void Edge_Clicked(object sender, EventArgs e)
{
CheckBox chkbox = FindCheckBoxThatCorrespondsToEdge((Edge)sender);
chkbox.Checked = !chkbox.Checked;
}
protected void chkEdge_CheckChanged(object sender, EventArgs e)
{
Edge edge = FindEdgeThatCorrespondsToCheckbox((CheckBox)sender);
OnToggleEdge(edge);
}
}
You can make an argument that the View knows too much about its implementation now: its aware that edges and checkboxes are fundamentally connected. Maybe this is another hack, but it can probably be dismissed as "UI logic" need to keep the View's display syncronized.