It seems that Marionette isn't designed to handle reusing views. What is an effective way to maintain view states (for all view types) since they're always being reconstructed?
My first thought was to capture state in the models, but I quickly parted with that idea as many views can reference the same model.
I did try reusing views in a couple of different fashions but wasn't confident what I was doing was correct. In each case, I felt like the Marionette methods I was overriding might break things (now and/or later).
I've found suggestions on how to accomplish this with pure Backbone, and also glanced at Giraffe which seems to handle state quite effectively, but I've yet to find a solution for Marionette.
An easy unsaved state system for getting data to the template is:
View.MyView = Marionette.ItemView.extend({
serializeData: function() {
return _.merge(this.model.toJSON(), this.options.state.toJSON());
},
});
var view = new View.MyView({
model: model,
state: new Backbone.Model(),
});
With a little more advanced version you can use the model events too:
View.MyView = Marionette.ItemView.extend({
initialize: function() {
var self = this;
this.options.state.on('change', function(event, data) {
if (_.isFunction(self[event])) {
self[event](data);
}
});
},
});
Then in your controller:
view.options.state.trigger('change', 'functionName', 'someData');
You can track your view states by using a ViewModel.
Sam talks a bit about this here: http://youtu.be/CTr-tTwRH3o
I have multiple backbone views that make up a screen, currently I am doing it like this:
render : function() {
this.$el.html(this.template());
this.view2 = new View2();
this.view2.render();
this.$el.append(this.view2.$el);
... more views added here as necessary
}
Is this the correct way to handle multiple views or is there a better way to attach views to the current view?
I want to be able to destory and recreate a view with the relevant HTML getting removed/added from the parent view without having to manually do it.
To be honest, i really recommend you to checkout Marionette features. I had an experience building large scale app with backbone, and can say it real magic wand in developments. It helps you avoid memory leaks working with views and make you code more compact and clear decreasing boilerplate code.
So in your case you can get Layout View, create regions and render views in regions.
var Layout = Marionette.Layout.extend({
regions: {
head: "#head",
main: "#main"
}
});
var layout = new Layout();
layout.render();
layout.main.show(new SomeView());
Many of the views in my application need to be "collapsible". To the user this means that you can click an arrow to collapse or expand the view's contents.
When creating a view I need to be able to easily say, "This view should be collapsible," and then run the appropriate setup code (which essentially means adding the .collapsible class to the view's wrapper and inserting a dom element that looks like this: <div class="toggle"></div>
Suggestions on ways to pull this off seamlessly? I'm currently using Backbone, Backbone.Marionette, and Underscore.
I do this with another application that doesn't use Backbone. In that application every action results in a page refresh, so I just use jQuery to look for all elements with the .collapsible class and do my setup that way.
EDIT:
I'm using Backbone.Marionette.CompositeView for these particular views, if that helps.
I've done similar thing in my project by extracting such functionality into mixins. There're different approaches to implementing mixins in Backbone. Take a look here or here
You can create parent view that extends from Marionettes compositeView and add your common functionallity there, and have your project views extend from this parent view.
var CollapsibleView = Backbone.Marionette.CompositeView.extends({
variable1: 1,
var2: true,
initialize : function() {
// your code here
},
helperfunction : function () {
// other helpful function
}
});
var MySpecificView = CollapsibleView.extends({
mySpecificFunction : function () {
// some specificView functionality
}
});
var myProjectView= new MySpecifcView();
myProjectView.helperfunction(); /// function from the parent
myProjectView.mySpecificFunction(); /// function from the specificView
/// you also have the functionality added on the initialization of the collpasibleView
So I know there are many ways for doing things in Backbone, but since I don't have the vast experience of many on here, I would like advice regarding a best approach.
I have a basic CRUD app where I have a form for adding data and a form for editing data, which are essentially the same. And actually are attached to the same DOM element.
So I could include the two forms into one view and serve the appropriate template, depending on whether the view has a model or not. Something like this:
var AddEditView = Backbone.View.extend ({
el: $("#add"),
template: $("editTemplate").html();
render: function() {
if (this.model) {
var theTmp = _.template(this.template)
this.$el.html(theTmp(this.model.toJSON()));
}
else {
var theTmp = _.template($("#addTemplate").html());
this.$el.html(theTmp);
}
},
});
I think this would work however I might run into some sticky issues with any events (i.e. events being bound twice).
Or I could create two completely separate views that would be attached to the same dom element and would toggle back and forth depending on the app state (way more lines of code).
What would you all recommend in this situation. Is more logic in a view better or more lines of code and less logic in views?
Assuming the fields are identical whether you're creating a new model or editing an existing one, I'd recommend having only one view, and only one template. When you instantiate the view, if you are creating a new model, just instantiate a new model and pass it to the view. Otherwise, pass the existing model.
var AddEditView = Backbone.View.extend ({
render: function() {
var theTmp = _.template(this.template)
this.$el.html(theTmp(this.model.toJSON()));
},
someSaveEvent: function() {
this.model.save(); // This will POST if the model isNew() or PUT otherwise
}
});
var model = new Model(); // If you're creating a new model
var addEditView = new AddEditView({
model: model
});
I'm just getting started with Backbone. I went through the first two PeepCode screencasts which were great and now I'm digging in on a quick detached (no server side) mock-up of a future app.
Here's what I'm looking to build (roughly). A series of five text boxes - lets call these Widgets. Each Widget input, when selected, will display a pane that shows Tasks associated with the Widget and allow the user to create a new Task or destroy existing Tasks.
At this point, I'm thinking I have the following models:
Widget
Task
The following collections:
Tasks
Widgets
The following views (this is where it gets hairy!)
WidgetListView
- Presents a collection of Widgets
WidgetView
- sub-view of WidgetListView to render a specific Widget
TaskPaneView
- Presented when the user selects a Widget input
TaskCreateView
- Ability to create a new Task associated with selected Widget
TaskListView
- Presents a collection of Tasks for the given widget
TaskView
- Displays Task detail - sub-view of TaskListView
Assuming that's reasonable, the trick becomes how to display a TaskPaneView when a WidgetView is selected. And futhermore, how that TaskPaneView should in turn render TaskCreateViews and TaskListViews.
The real question here is: Does one cascade render events across Views? Is it permissible for a Root view to know of sub-views and render them explicitly? Should this be event-driven?
Apologies if this is an open-ended question, just hoping someone will have seen something similar before and be able to point me in the right direction.
Thanks!
Definitely make it event driven. Also, try not to create views that are closely coupled. Loose coupling will make your code more maintainable as well as flexible.
Check out this post on the event aggregator model and backbone:
http://lostechies.com/derickbailey/2011/07/19/references-routing-and-the-event-aggregator-coordinating-views-in-backbone-js/
The short version is you can do this:
var vent = _.extend({}, Backbone.Events);
and use vent.trigger and vent.bind to control your app.
Pre p.s.: I have made a gist for you with the code that I wrote below:
https://gist.github.com/2863979
I agree with the pub/sub ('Observer pattern') that is suggested by the other answers. I would however also use the power of Require.js along with Backbone.
Addy Osmani has written a few GREAT! resources about Javascript design patterns and about building Backbone applications:
http://addyosmani.com/resources/essentialjsdesignpatterns/book/
http://addyosmani.com/writing-modular-js/
http://addyosmani.github.com/backbone-fundamentals/
The cool thing about using AMD (implemented in Require.js) along with Backbone is that you solve a few problems that you'd normally have.
Normally you will define classes and store these in some sort of namespaced way, e.g.:
MyApp.controllers.Tasks = Backbone.Controller.extend({})
This is fine, as long as you define most things in one file, when you start adding more and more different files to the mix it gets less robust and you have to start paying attention to how you load in different files, controllers\Tasks.js after models\Task.js etc. You could of course compile all the files in proper order, etc, but it is far from perfect.
On top of this, the problem with the non AMD way is that you have to nest Views inside of each other more tightly. Lets say:
MyApp.classes.views.TaskList = Backbone.View.extend({
// do stuff
});
MyApp.views.App = Backbone.View.extend({
el: '#app',
initialize: function(){
_.bindAll(this, 'render');
this.task_list = new MyApp.classes.views.TaskList();
},
render: function(){
this.task_list.render();
}
});
window.app = new MyApp.views.App();
All good and well, but this can become a nightmare.
With AMD you can define a module and give it a few dependencies, if you are interested in how this works read the above links, but the above example would look like this:
// file: views/TaskList.js
define([], function(){
var TaskList = Backbone.View.extend({
//do stuff
});
return new TaskList();
});
// file: views/App.js
define(['views/TaskList'], function(TaskListView){
var App = Backbone.View.extend({
el: '#app',
initialize: function(){
_.bindAll(this, 'render');
},
render: function(){
TaskListView.render();
}
});
return new App();
});
// called in index.html
Require(['views/App'], function(AppView){
window.app = AppView;
});
Notice that in the case of views you'd return instances, I do this for collections too, but for models I'd return classes:
// file: models/Task.js
define([], function(){
var Task = Backbone.Model.extend({
//do stuff
});
return Task;
});
This may seem a bit much at first, and people may think 'wow this is overkill'. But the true power becomes clear when you have to use the same objects in many different modules, for example collections:
// file: models/Task.js
define([], function(){
var Task = Backbone.Model.extend({
//do stuff
});
return Task;
});
// file: collections/Tasks.js
define(['models/Task'], function(TaskModel){
var Tasks = Backbone.Collection.extend({
model: TaskModel
});
return new Tasks();
});
// file: views/TaskList.js
define(['collections/Tasks'], function(Tasks){
var TaskList = Backbone.View.extend({
render: function(){
_.each(Tasks.models, function(task, index){
// do something with each task
});
}
});
return new TaskList();
});
// file: views/statistics.js
define(['collections/Tasks'], function(Tasks){
var TaskStats = Backbone.View.extend({
el: document.createElement('div'),
// Note that you'd have this function in your collection normally (demo)
getStats: function(){
totals = {
all: Tasks.models.length
done: _.filter(Tasks, function(task){ return task.get('done'); });
};
return totals;
},
render: function(){
var stats = this.getStats();
// do something in a view with the stats.
}
});
return new TaskStats();
});
Note that the 'Tasks' object is exactly the same in both views, so the same models, state, etc. This is a lot nicer than having to create instances of the Tasks collection at one point and then reference it through the whole application all the time.
At least for me using Require.js with Backbone has taken away a gigantic piece of the puzzling with where to instantiate what. Using modules for this is very very helpful. I hope this is applicable to your question as well.
p.s. please also note that you'd include Backbone, Underscore and jQuery as modules to your app too, although you don't have to, you can just load them in using the normal script tags.
For something with this kind of complexity, I might recommend using Backbone Aura, which has not yet had a stable release version. Aura essentially allows you to have multiple fully self-contained Backbone apps, called "widgets," running on a single page, which might help disentangle and smooth over some of your model/view logic.
From a classical MVC perspective, your views respond to changes in their associated models.
//initialize for view
initialize : function() {
this.model.on("change", this.render(), this);
}
The idea here is that anytime a view's model is changed, it'll render itself.
Alternatively or additionally, if you change something on a view, you can trigger an event that the controller listens to. If the controller also created the other models, it can modify them in some meaningful way, then if you're listening for changes to the models the views will change as well.
Similar answer to Chris Biscardi's. Here's what I have:
You create a global var Dispatcher (doesn't have to be global as long as it can be accessed from the scope of Backbone app):
Dispatcher = _.extend({}, Backbone.Events);
Dispatcher will help you execute subscribed callbacks with events that are not particularly triggered by changes in models or collections. And cool thing is that Dispatcher can execute any function, inside or outside Backbone app.
You subscribe to events using bind() in a view or any part of the app:
Dispatcher.bind('editor_keypress', this.validate_summary);
Then in another view or part of the app you trigger new event using trigger():
Dispatcher.trigger('redactor_keypress');
The beauty of using a dispatcher is its simplicity and ability to subscribe multiple listeners (e.g. callbacks in different Backbone views) to the same event.