Backbone AutoUpdatedCollection

AutoUpdatedCollection.js

/*
  In the scenario you have a _shared Collection_ which contains every Model of one class, 
  and this Collection is used to populate _sub-Collections_ those have to be _updated_ 
  when the shared Collection is updated.
*/

App.AutoUpdatedCollection = Backbone.Model.extend({
  initialize: function( opts ){
    this.name                 = opts.name;
    this.sourceCollection     = opts.sourceCollection;
    this.filterField          = opts.filterField;
    this.filterValue          = opts.filterValue;

    this.filteredCollection   = new Backbone.Collection;
    this.filteredCollection.reset( this.filterCollection() );

    this.sourceCollection.on( "change:" + this.filterField, this.filterModel, this );
    this.sourceCollection.on( "remove", this.removeModel, this );
    this.sourceCollection.on( "add", this.addModel, this );
  },

  filterCollection: function(){
    console.log( "AutoUpdatedCollection.filterCollection", this.name );

    // var _self = this;
    var result =
      this.sourceCollection.filter( function( model ) {
        return model.get( this.filterField ) == this.filterValue;
      }, this);

    console.log( "AutoUpdatedCollection.filterCollection.result", this.name, result.length, result );

    return result;
  },

  filterModel: function( model, val ){
    console.log( "AutoUpdatedCollection.filterModel", this.name, model.id, val );

    if( val == this.filterValue ){
      this.addModel( model );
    } else {
      this.removeModel( model );
    }
  },

  removeModel: function( model ){
    if( this.filteredCollection.get( model.id ) ){
      console.log( "AutoUpdatedCollection.removeModel", this.name, model.id );
      this.filteredCollection.remove( model );
    }
  },

  addModel: function( model ){
    if( model.get( this.filterField ) == this.filterValue ){
      console.log( "AutoUpdatedCollection.addModel", this.name, model.id, Math.random() );

      this.filteredCollection.add( model );
    }
  }
});