Backbone.observe

Extends Backbone.Collection with an observe method which creates new collection that is automatically synced, optionally filtered and optionally transformed from the original collection.

The observe method accepts the following options (all optional):

• filter
• map
• collection

observe method options

filter

The filter function is given the original model from the source collection.

var specialDocs = docs.observe({
  filter: function(doc){
    return doc.attributes.special;
  }
});

docs.reset([ { title: 'lorem', special: true }, { title: 'ipsum' } ]);

console.log(docs.length); 
// 2

console.log(specialDocs.length); 
// 1

map

The map function is passed two parameters:

1. A copy of the attributes created with model.toJSON().
   These attributes are safe to modify and return.

2. The model from the source collection

var importantDocs = docs.observe({
  map: function(attributes){
    attributes.title += '!!!';
    return attributes;
  }
});

docs.reset([ { title: 'lorem', id: 1 } ]);

console.log(importantDocs.get(1).get('title')); 
// lorem!!!

docs.get(1).set('title', 'Lorem Ipsum');

console.log(importantDocs.get(1).get('title')); 
// Lorem Ipsum!!!

collection

The collection option can be used to provide an existing collection to observe the source collection. If the collection is not used a new collection will be created automatically.

observing collection methods

dispose

A dispose method is added to the observing collection which should be used to unbind the observing collection from the source collection.

var observingCollection = sourceCollection.observe();

// ...

// Call dispose to disconnect observingCollection from sourceCollection
observingCollection.dispose();

License

MIT license