Backbone GroupedCollection is for creating dynamic data strcutures like this.

In which you have a collection and you want to group the models in the collection into an arbitrary number of groups, based on attributes of the models.

Using this library allows you to do some things that could get quite complicated if not, for example:

• Sorting groups and models in groups seperately
• Appending new models to the right group automatically
• Adding and removing groups when models are added or removed
• Creating a dynamic tree that responds to change events in the models

Backbone.buildGroupedCollection recieves a base collection and a groupBy function. It returns a collection of models (groups). Each of the groups has it's group identifier as the id, and a special property vc which is a Backbone.VirtualCollection of the models that belong in the group.

It works well with Marionette or stand-alone.

var animals = new Backbone.Collection([
  {name: 'cat', color: 'black'},
  {name: 'dog', color: 'black'},
  {name: 'bird', color: 'red'}
]);

var grouped_animals = Backbone.buildGroupedCollection({
  collection: animals
, groupBy: function (animal) {
    return animal.get('color');
  }
});

The structure looks something like this:

• GroupCollection
  • Group (black)
    • Animal (cat)
    • Animal (dog)
  • Group (red)
    • Animal (bird)

And the structure adapts itself constantly to changes in the base colleciton.

grouped_animals.pluck('id'); // ['black', 'red']
grouped_animals.get('black').vc.length; // 2
grouped_animals.get('red').vc.length; // 1

// adding elements
animals.add({name: 'dinosaur', color: 'green'});
grouped_animals.pluck('id'); // ['black', 'red', 'green']
grouped_animals.get('green').vc.at(0) === animals.findWhere({name: 'dinosaur'}); // true

// removing elements
animals.remove(animals.findWhere({name: 'cat'}));
grouped_animals.pluck('id'); // ['black', 'green']

Somtimes you want to make sub-groups, or infinitely nested groups. For example, you have a shopping list that you want grouped by store, and then within each store, by item type.

var grouped_shopping_list = Backbone.buildGroupedCollection({
  collection: shopping_list,
, groupBy: groupByShop
, GroupModel: Backbone.Model.extend({
    initialize: function (options) {
      // options.id is the group id
      // options.vc is the  virtual collection
      this.grouped_vc = Backbone.buildGroupedCollection({
        collection: options.vc
      , groupBy: groupByItemType
      })
    }
  })
});

// the items of type "office supplies" from the store "home depot" will be accesible at

grouped_shopping_list.get('home_depot').grouped_vc.get('office_supplies') // retutns a virtual collection

The base collection.

The function that defines the grouping. It recieves a model as the argument, and it must return the id of the group it belongs to.

The GroupCollection will continue listening to the base collection untill you call stopListening() on it. You can bind the lifespan of a grouped_collection to that of a marionette view by specifying a close_with option. (it can also be any event emitter that emits a close or destroy event)

Specifies an alternative 'class' for the GroupCollection to have. It should extend from Backbone.Collection.

Specifes an alternative 'class' for the Groups to have. It should extend from Backbone.Model;

Object passed to the virtual collections as options. Use this to configure comparators, etc.

0.1.4 Added comparator option via @masylum
0.1.3 Change package name to allow publishing on npm
0.1.2 Add vc_options via @masylum. Fix close_with handling
0.1.1 Add listeners for 'change', 'remove' and 'reset' only once
0.1.0 Fixes groups not being deleted because a race condition with `VirtualCollection`
0.0.3 Fixes bug when changing a model failed to create a new Group
0.0.2 Add GroupCollection & Group options

The MIT License (MIT)

Copyright (c) 2013 Pedro [email protected]

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

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