I bind the collection to a DOM element '#collection_view'.
When collection fetching data and update the view, the view changed to be EMPTY for a second and then filled with correct HTML.
In the collection there are addAll, addOne methods to append list element to the list.
How can I skip the empty, replace old HTML with new HTML directly?
This is how fetch() works.. it will empty the collection and addAll elements at once. I suppose you have a this.$el.empty() call (or something like) in your addAll event binding function. And what is happening is that the $el DOM element will be cleaned and after that repopulated.
If you want to refresh a collection instead of reset it you should check the answers here.
Looks like someone proposed to add this soft update to the Backbone Collection but was denied by Backbone maintainers.
Related
I am using ng-repeat for my Model render in angular ,
if i Push new Element in Model/Collection , Will angular only deal with Update or Loop through the whole model again.??
My experience (using Angular version 1.2.7) is such that whenever something changed in collection, the whole ng-repeat was repainted.
You can easily test it by modifying the generated DOM. For example by adding custom attributes like my-id="1", my-id="2" etc to the DOM elements.
Then change something in your collection, which will trigger new $digest cycle.
Angular will pick up the change and redraw the DOM -> your custom attributes will disappear.
So I would argue that Angular loops through the whole model.
In the documentation it is clearly mentioned:
ngRepeat
ngRepeat directive instantiates a template once per item from a collection. Each template instance gets its own scope
Angular associates an identity to every item, the elements already associated to the existing items of the collection won't be recreated.
Hence, only elements that are removed from the collection, are removed from the DOM. Furthermore, if an item moves within the collection it doesn’t need a new scope, but it needs to be moved in the DOM.
I construct a CompositeView by passing it a collection. The collection gets its data via a url. I'm using the defer/promise technique to wait till the collection is populated before constructing the View.
Later I call fetch on the collection again, modifying the url.
To my surprise the CompositeView is re-rendered with the new data in the Collection. I thought I would have to do something e.g.:
collectionEvents: {
"sync" : "render"
}
But I'm not doing anything. No event binding at all. I thought in marionette I would have to handle this 'manually'.
This looks like something to do with CollectionView: Automatic Rendering. Does this happen with models and item views as well? And why do some tutorials etc. explain about binding?
Thanks
--Justin Wyllie
Yes but the only thing that will be re-rendered will be the collection, if you are using a CompositeView to display a model and a collection, the model part will not be re-rendered, you have to set an event for that.
So the CompositeView has the same behavior of the collectionView and it will re-render the collection whenever theres a change in the data.
And to your second question this does not happens in the ItemViews when the model changes.
this you have to do it on your own when its best for you application needs.
On adding new model to my collection I don't want the view to be refreshed but I want the model to be appended to my collection and be appended to the view. SO i shouldn't render the view again. Is it possible via Backbone.js? How should I proceed ?
You could have a view that handles the whole layout, and a view that represents a single model. You would make the render method of the latter to return the HTML of a single model, and append the result to a list using the main view. You have a great example of this in the Addy Osmani's book "Developing Backbone.js applications". Take a look at the section where he explains how he renders each task to the todo list of his Todo App, if I understood well, your problem is solved in there.
I have a Backbone view which represents a collection. When this collection is synced with the server, and new models are added to the collection, I would like to hide all the view instances that represent these new models in the collection, whilst continuing to display the old models' view instances. How can I do this?
I'm assuming you're using a Marionette.CollectionView or Marionette.CompositeView here, right? That being the case, you are trying to prevent these from showing the newly added models, when the come back from the server and are added to your collection, right?
I can see a few different ways of doing this, most of which begin at the same place: a collection that filters based on an attribute that tells you whether or not to show the model. You would need to have some piece of data on the models that tells you wether to show them or not... I'm not sure what this would look like off-hand, but once you have the logic set up for this, I think the rest of it becomes easier.
A Proxy Collection
My preferred method of handling this in the CompositeView or CollectionView would be to create the view instance with a proxy collection - one that is filtered based on the value to show or hide the models.
I've talked about proxy collections before, and I have a working JSFiddle to show how to build them, here: http://jsfiddle.net/derickbailey/7tvzF/
You would set up a filtered collection like this, and then send the filtered collection to your actual view instance:
var filtered = new FilteredCollection(myOriginalCollection);
filtered.filter({
showThisOne: true
});
var view = new MyCompositeView({
collection: filtered
});
myOriginalCollection.fetch();
From here, it comes down to how you want to manage the filtering and fetch/sync of the original collection. But I think the over-all solution hinges on the proxy/decorator collection and being able to filter the collection down to only the list of items that you want.
Views in Bbone are not automatically updated when the underlying model/collection is changed. You have to explicitly listen for events: change/destroy for models and add/change/remove/reset for collections and call render().
As WiredPrairie suggests, if you've registered during view initialization for example to listenTo() any of these events and explicitly render(), you can always use stopListening() to reverse the effect.
An alternative, in case it's a one-of case of suppressing the view from showing the changes, is to check manually in your view's render() which models have been changed and use the previous state of the changed attributes to avoid showing the new values. Check out: model.hasChanged() and model.previousAttributes() as well as the options.previousModels in case of a collection reset.
I'm new to backbone and am a bit stuck. Basically I want to update a collection on the change of a select. Currently on the change of the select I call Collection.fetch() but this appends the new models in the view. I was under the impression that when fetch is called, it removes the previous models which should then cause the related views to be removed, or am I incorrect?
Any help is appreciated!
It does by default, unless you've specified {add: true}.
The reason that the elements are being appended in the view will be because you are appending them without clearing out the old. When the reset event is fired in your view you could consider emptying your container before appending.
Remember, with backbone you are handling the DOM manipulation yourself. The View is not automagically updated along with your Collections & Models.