Backbone VirtualCollection allows you display a subset of a Backbone collection in a Backbone view that updates in real time. It works great with Marionette CollectionViews.
VirtualCollection 0.5 is a complete re-write of VirtualCollection that brings a lot of improvements.
- Inherits from Backbone.Collection
- More efficient data structures
- More intelligent sort handling (special thanks to @disruptek)
- Better performance for nested virtual collections
- More extensive test coverage
All that in half the lines of code!
Every effort has been made to maintain compatibility with v0.4, and in most cases it'll be a drop-in replacement. However, there are a few changes that have been made.
virtual_collection.models() is now virtual_collection.models, just like Backbone
For example, let's say you have a task collection, and want to show a list of tasks that belong to a specific user.
We can instantiate a virtual collection that only contains tasks that belong to Rupert (who has user_id 13).
The constructor takes two parameters, the first is the parent collection, the second is a options object. The filter option specifies a function that takes the model as argument. You can also just specify a hash of attributes to match.
var virtual_collection = new VirtualCollection(tasks_collection, {
filter: function (task) {
return task.get('user_id') == 13;
}
});
// or using a hash of attributes to match
virtual_collection = new VirtualCollection(tasks_collection, {
filter: {
user_id: 13
}
});
var view = new TaskListView({
collection: virtual_collection
});The Marionette collection view will only display the tasks that belong to Rupert, and it will update automatically. In other words, when a task is created that belongs to Rupert it will appear, but not if it belongs to Bob.
Be default, the virtual collection will have the same sorting order as the parent collection. However, a comparator can be specified to change this. The comparator behaves like a Backbone comparator. In other words, you can specify a function or the name of an attribute to sort by.
var virtual_collection = new VirtualCollection(tasks_collection, {
filter: { user_id: 13 },
comparator: 'name'
});
// tasks in the virtual_collection will be sorted by nameYou can also change the sorting order on the fly.
virtual_collection.comparator = 'created_at';
virtual_collection.sort(); // triggers sort event
// virtual_collection is now sorted by date, but the parent collection has not changedThe virtual collection will keep listening to its parent collection until you call stopListening.
You can use the helper function virtual_collection.destroyWith to tell the collection to stopListening when a Marionette view is destroyed.
var virtual_collection = new VirtualCollection(collection, {filter: {foo: 'bar'}});
var view = new Marionette.CollectionView({collection: virtual_collection});
virtual_collection.destroyWith(view);Using the helper will take care of unbinding the virtual collection's listeners when the view is destroyed.
You also can pass a destroy_with option when creating the virtual collection being that an event emitter. The virtual collection will stop listening to events when the destroy_with event emitter emits a destroy event.
var virtual_collection = new Backbone.VirtualCollection(collection, {
filter: {foo: 'bar'},
destroy_with: view
});+Note: Prior to Marionette 2.*, "destroy" was called "close". For compatibility with older versions of Marionette, the old helper virtual_collection.closeWith and option close_with are still availble, handling the close event.
It's very common that you'd want to update the filter being used and have the collection view update itself. updateFilter takes the same parameters as the original filter option (a hash, or a function) and regenerates the virtual collection without losing your view bindings.
virtual_collection.updateFilter({
the_new: 'properties'
, are: 'lovely'
});
// or
virtual_collection.updateFilter(function (model) {
return model.foo() === 'bar';
});VirtualCollection does not store, or duplicate any data. We've used other solutions in the past, and duplicating data is just plain bad news.
VirtualCollection maintains an internal index of models that pass the filter. That way, using the accessors and iterators (map, each, etc) is fast. It doesn't have to go through the whole parent collection and re-evaluate all the filters.
Happy hacking!
0.5.1 Ignore change events with malformed arguments
0.5.0
- VirtualCollection extends Backbone.Collection
- .models() is now .models array instead
- faster .get()
- faster ._onAdd()
- faster nested collections
- smarter sorting (thanks @disruptek)
0.4.15 Added virtual_collection.model (via @fcsonline)
0.4.14 Added Backbone.extend (via @enov)
0.4.13 Optimized `_models` and `get` to access parent collections which are indexed
0.4.12 Pass the correct index in options object on model removal
0.4.11 Trigger `reset` in updateFilter (fixes issue with multilayer filtering)
0.4.10 Added Bower support
0.4.9 Added `where` and `findWhere`. Renamed internal filterFunction
0.4.8 Add `add` and `remove` proxies. Add index argument to filter function.
0.4.7 Add the updateFilter method (via @justinwinslow)
0.4.6 Add toJSON method (via @gbedardsice)
0.4.5 Add close_with option
0.4.4 Add all collection Underscore iterator proxies
0.4.3 Fix bug with onChange handler not proxying add and remove events correctly
0.4.2 Improve importing with npm
0.4.0 Make filter part of options hash. This version breaks backwards compatibility. You'll have to update your code.
0.3.3 Fix sort comparator with two args. Add more iterator helper functions
0.3.2 Fix reset event on parent collection
0.3.1 Replace viewHelper with closeWith
0.3.0 Fix unbinding of index listeners
0.2.0 Use cid instead of ids
0.1.1 Fixed issues with comparators specified as a function
0.1.0 Added support for comparators & sorting, separate from the parent collection
0.0.2 Fix buildFilterFromHash not detecting null values
- discuss/edit/merge PR's
npm version patch- update changelog in README.md
- update version number in component.json, bower.json
git push && git push --tags- npm publish
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