Develop Reference

Preventing Marionette CompositeView render until fetch complete

I'm having a problem where render is being called autimatically in my Marionette CompositeView which is correct, the problem is that I'm fetching collection data in the initialize and want this to be present when the render happens. At the moment I'm running this.render() inside the done method of the fetch which re-renders but this causes problems as now I have 2 views per model. Can anyone recommend how I can properly prevent this initial render or prevent the duplicate views. 1 entry will output view1 and view2.
JS CompositeView
initialize: function() {
var self = this;
this.teamsCollection = new TeamsCollection();
this.teamsCollection.fetch().done(function() {
self.render();
});
},

First of all, I don't believe there is a way to stop rendering outright, but you have a bunch ways around that.
Option 1: fetch data first, then create your view and pass data into it when it's done.
//before view is rendered, this is outside of your view code.
var teamsCollection = new TeamsCollection();
teamsCollection.fetch().done(function(results) {
var options = {res: results};
var myView = new CompositeView(options);
myView.setElement( /* your element here */ ).render();
});
Option 2:
// don't use render method, use your own
initialize: function() {
var self = this;
this.teamsCollection = new TeamsCollection();
this.teamsCollection.fetch().done(function() {
self.doRender();
});
},
render: function(){}, // do nothing
doRender: function(){
// override render here rather than using default
}
Option 3: (if using template)
// if you have a template, then you can simply pass in a blank one on initialization
// then when the fetch is complete, replace the template and call render again
initialize: function() {
var self = this;
this.template = "<div></div"; // or anything else really
this.teamsCollection = new TeamsCollection();
this.teamsCollection.fetch().done(function() {
self.template = /* my template */;
self.render();
});
},
In reality I need more info. How is the view created? is it a region? is it added dynamically on the fly? Do you use templates? Can you provide any more code?

Backbone: Re-render existing model in new DOM element

I am using a collection view to render my array of model views. I have added a method that removes a single model view from the existing collection view, and attempts to re-render it in a new el: element.
I use collection.get(this.model) to save the model to a variable, I add that variable to my new collection which is the model of a new collection view associated with a new DOM element, and I re-use the same collection view render method. When I console.log() the new collection, I see the model that I picked from the old collection, but it's not rendering on the page.
<script>
(function($){
//---------SINGLE ENTRY MODEL----------
var Entry = Backbone.Model.extend({
defaults: function(){
return{
word: '',
definition: ''
}
}
});
//------------ENTRY MODEL COLLECTION------------
var EntryList = Backbone.Collection.extend({
model: Entry
});
//-----INSTANCIATE COLLECTION----
var dictionary = new EntryList();
var saved = new EntryList();
//-----SINGLE ENTRY VIEW------
var EntryView = Backbone.View.extend({
model: new Entry(),
tagName:'div',
events:{
'click .edit': 'edit',
'click .delete': 'delete',
'keypress .definition': 'updateOnEnter',
'click .save': 'save'
},
delete: function(ev){
ev.preventDefault;
dictionary.remove(this.model);
},
edit: function(ev){
ev.preventDefault;
this.$('.definition').attr('contenteditable', true).focus();
},
//method that adds existing model to new collection
save: function(ev){
ev.preventDefault;
var savedEntry = dictionary.get(this.model);
dictionary.remove(this.model);
saved.add(savedEntry);
console.log(savedEntry.toJSON());
},
close: function(){
var definition = this.$('.definition').text();
this.model.set('definition', definition);
this.$('.definition').attr('contenteditable', false).blur();
},
updateOnEnter: function(ev){
if(ev.which == 13){
this.close();
}
},
initialize: function(){
this.template = _.template($("#dictionary_template").html());
},
render: function(){
this.$el.html(this.template(this.model.toJSON()));
return this;
}
});
//--------------DICTIONARY VIEW------------
var DictionaryView = Backbone.View.extend({
model: dictionary,
el: $('#entries'),
initialize: function(){
this.model.on('add', this.render, this);
this.model.on('remove', this.render, this);
},
render: function(){
var self = this;
self.$el.html('');
_.each(this.model.toArray(), function(entry, i){
self.$el.append((new EntryView({model: entry})).render().$el);
});
return this;
}
});
//---------SAVED ENTRY VIEW-----------
var SavedView = Backbone.View.extend({
model: saved,
el: $('#saved'),
initialize: function(){
this.model.on('save', this.savedRender, this);
},
//method that renders new collection view with different el:
savedRender: function(){
var self = this;
self.$el.html('');
_.each(this.model.toArray(), function(saved, i){
self.$el.append((new EntryView({model: savedEntry})).render().$el);
});
return this;
}
});
//-------BINDING DATA ENTRY TO NEW MODEL VIEW-------
$(document).ready(function(){
$('#new-entry').submit(function(ev){
var entry = new Entry({word: $('#word').val(), definition: $('#definition').val() });
dictionary.add(entry);
dictionary.comparator = 'word';
console.log(dictionary.toJSON());
$('.form-group').children('input').val('');
return false;
});
var appView = new DictionaryView();
});
//--------------ROUTER----------------
var Router = Backbone.Router.extend({
routes:{
'':'home'
}
});
var router = new Router();
router.on('route:home', function(){
console.log('router home');
});
Backbone.history.start();
})(jQuery);
</script>

There are a number of problems here.
First, you do not have an instance of SavedView. The var SavedView = Backbone.View.extend(...); statement is just defining the SavedView class. In order to have a living instance of this class, you must initialize one with the new operator. You will need a line like the following somewhere in your code (a good place would be at the end of the jQuery ready handler):
var saved_view = new SavedView();
Next, we will investigate the save method of the EntryView class. The var savedEntry = dictionary.get(this.model); statement is completely unnecessary because we know that dictionary.get(this.model) will return this.model - which we obviously already have an instance of. So we can remove the clutter from this method and be left with the following:
ev.preventDefault;
saved.add(this.model);
dictionary.remove(this.model);
However, we are still not at our destination. If we turn our attention to the SavedView class definition, we see that it is binding its render method to the 'save' event on its collection, the saved object. Its not the 'save' event we should be binding to, but rather the 'add' event - as that is what will be triggered when we add models to saved:
this.model.on('add', this.savedRender, this);
If we test our code now we should get scolded with a reference error on savedEntry within SavedView.savedRender. It looks like this is a typo and what was intended was `saved'. (You will notice below that in addition to correcting the typo, I have also removed a set of parentheses from this expression that served no function save for making the code less readable):
self.$el.append(new EntryView({ model: saved }).render().$el);
EDIT:
In response to your follow-up question about the saved variable inside the SavedView.savedRender method:
The saved object in this case is a single Entry model. The reason for your confusion is that we are re-using the variable name "saved". Within the _.each callback we have defined the first parameter to be called "saved"; this "saved" is local to the callback and is not related to the EntryList collection defined previously. Within our callback, saved is an element of the saved collection (yikes!) - which is a lesson in why variable naming is important.
As I proceeded to change the name of "saved" in the savedRender method, I noticed a few other refactorings that were screaming to be made. I have listed my refactorings below:
A purpose of using Backbone (http://backbonejs.org/) is to give us access to convenient helpers for objects (models) and arrays (collections). Backbone collections have an each method we can make use of instead of passing our collection to Underscore's (http://underscorejs.org/) each.
As stated above, saved is a terrible name for our each callback parameter because it conflicts conceptually with the name of the collection. Because saved is a collection of Entry models, "entry" is a much more suitable name.
Backbone allows us to pass the context to our each callback that will be our this within that callback. This allows us to skip the step of caching our this in the self variable.
My refactored savedRender becomes:
savedRender: function () {
this.$el.empty();
this.model.each(function (entry) {
this.$el.append(new EntryView({ model: entry }).render().$el);
}, this);
return this;
}

Referencing object from within another object

I am creating a view in backbone that accepts a collection I want to then render that view then use the collection to append another view to the orginal but I don't know how to reference the original view in the success function of the collection. When I try the following code I get undefined.
new GenreView().render(new PopVideosCollection());
define (['jquery','underscore','backbone'],function($,_,Backbone) {
GenreView = Backbone.View.extend({
tagName:"div",
className:"sect",
template: _.template($("#genreView").html()),
render: function (collection)
{
this.$el.html(this.template);
collection.fetch ({success:function (video)
{
console.log(video.toJSON());
console.log(GenreView.el);
},
});
},
});
return GenreView;
});

You need to get a reference to the instance of GenreView from inside the callback. Something like this should get you there:
var context = this;
collection.fetch ({success:function (video){
console.log(video.toJSON());
console.log(context.el);
}
});
However, you should re-think your approach a little. It would be better to call fetch on your collection, and have the view subscribe the reset event of your collection. Starting with your example code, that would look something like:
var GenreView = Backbone.View.extend({
initialize: function() {
this.listenTo(this.model, "reset", this.appendSubView);
},
render: function() {
this.model.fetch();
},
appendSubView : function(video){
console.log(video.toJSON());
console.log(this.el);
}
});

templateHelpers in Marionette.CompositeView

I have no idea why this code is not working.
Reading the documentation,
the templateHelpers should be called.
My goal is to pass the this.collection.length to the template.
Any hints? thanks.
I am using Backbone.Marionette v0.9.5
return Marionette.CompositeView.extend({
className: 'user-board',
template: usersTemplate,
itemView: userItemView,
initialize: function () {
this.collection = new UseList();
this.collection.fetch();
},
appendHtml: function (collectionView, itemView) {
collectionView.$el.find('ul.users-list').append(itemView.el);
},
templateHelpers: function () {
console.log(this.collection.length);
},
serializeData: function () {
return {
weekly: this.options.weekly,
users_length: this.collection.length // here the length is zero
// after the fetch the length is > 0
// but in template remains 0
};
}
});
To fix my issue I have to make the following...
initialize: function () {
_.bindAll(this, 'render');
this.collection = new NewCollection();
this.collection.fetch({
success: this.render
});
}
Is there a better way to make it working?

Reading the Marionette Documentation serializeData method, which is the one using mixinTemplateHelpers, is only called on Item View.render method here and in your current code you do not render at all
UPDATE:
This way everytime the collection receives new data it will update your view the new length
initialize: function () {
_.bindAll(this, 'render');
this.collection = new NewCollection();
this.collection.fetch();
this.collection.bind('reset', this.render);
}

This code only declares the a view. Can you share the code the instantiates the view and displays it? templateHelpers will be called and the data passed to the template when the template is rendered. That is, you either need to show the view in a region which implicitly calls the render method on the view, or explicitly call the render method.
To be useful, templateHelpers should return an object. For instance:
templateHelpers: function() {
return {colLength: this.collection.length};
}
One important thing to keep in mind: fetch trigger an AJAX request that is done asynchronously. If you want to wait for the fetch to succeed before rendering the view, then you need to use Marionette.Async.
Update based on the update question
To avoid calling render from the view's initialize and only do it when render is called externally, change your code to:
return Marionette.CompositeView.extend({
className: 'user-board',
template: usersTemplate,
itemView: userItemView,
initialize: function () {
this.collection = new UseList();
var that = this;
this.defer = $.Deferred();
this.collection.fetch({
success: that.defer.resolve,
error: that.defer.resolve
});
},
appendHtml: function (collectionView, itemView) {
collectionView.$el.find('ul.users-list').append(itemView.el);
},
templateHelpers: function () {
console.log(this.collection.length);
// For greater flexibility and maintainability, don't override `serializeData`.
return {
weekly: this.options.weekly,
users_length: this.collection.length
};
},
render: function() {
var that = this,
args = arguments;
$.when(this.defer).done(function() {
Marionette.CompositeView.prototype.apply(that, args);
});
}
});
I'm resolving this.render both on success and error, otherwise if there is an error the view will never render (unless that's what you want).
Note that if you use Marionette.Async then you would return this.defer in the view's beforeRender and Marionette.Async would take care of delaying the rendering.
Also note that once this.defer is resolved, future renders will run when called as there is nothing to wait for, until this.defer has been reset programmatically.

At least in Marionette v1.0.3, I'm liking the pattern that rendering is handled automatically during a call to Region.show(), so I call that from a controller object which has the collection and passes it to the view on instantiation then shows the view. I don't even have to put this logic in a fetch success callback or explicitly bind to the 'reset' event, because the Marionette composite/collection view already knows to (re-)render itself on fetch success (which a debugger will show you).

After using a setup like has been detailed, you can also use template helpers a bit more usefully than has been described so far.
For example,
If you simply drop in <%= functionName %> into the template where you are trying to get the number to show up visually on the front end page (since you want .length I see), marionette will simply do the work for you.
So like this:
--Template File--
<div id="followerCount"> <%= showCount %> </div>
--Helper Function in View--
templateHelpers: {
showCount: function(){
return this.collection.length;
}
}
Hope that made sense or at least helps someone else perhaps looking for a simpler way to integrate database returned json to their templates.

Swap a view's model?

Basically I'm trying to figure out the best way to swap a model and react to that event.
class View extends Backbone.View
initialize: ()->
#do stuff
swapModel: (newModel)->
#model = newModel
view = new View({model:firstModel})
view.swapModel(newModel)
Is this all I have to do to swap out a view's model? Are there any other side effects I should plan for? What would be the best way to respond to this swap? Should I trigger a swap event in swapModel?
Thanks!

Don't swap models in a view. You'll run in to all kinds of problems related to DOM event, Model events in the view, etc. I've tried to do this a dozen times or more, and in every single case, I re-wrote my code so that I would create a new view instance for each model. The code was cleaner, simpler, easier to understand and easier to maintain and work with.

A very simple example of one way to do it. Why are you trying to swap models though?
MyView = Backbone.View.extend({
initialize: function() {
this.myTrigger = {};
_.extend(this.myTrigger, Backbone.Events);
this.myTrigger.on("modelChange", function(msg) {
alert("Triggered " + msg);
},this);
},
swapModel: function(model) {
// do something with model
// then trigger listeners
this.myTrigger.trigger("modelChange", "a model change event");
}
});
var myview = new MyView()
myview.swapModel()

You could use a collection that only allows one model. This way you don't touch the model and can call render as many times as you want. Something like this:
var SpecialCollection = Backbone.Collection.extend({
swap: function (model) {
//remove all models
this.reset();
//add one model
this.add(model);
}
});
var MyView = Backbone.View.extend({
initialize: function(){
this.listenTo(this.collection, 'add', this.render);
},
render: function() {
this.model = this.collection.first()
//do your normal rendering here
}
});
var c = new SpecialCollection();
var v = new MyView({collection: c});
c.swap({name: 'Sam'});
//view should render
c.swap({name: 'Dave'});
//view should render
You could lock down the Collection rules a bit further but I think it serves as a good example to get you going.