src code

class method ActiveRecord.Model.addIndex 

ActiveRecord.Model.addIndex(name,index,callbacks) → null
  • index_name (name)
  • index (Object)
  • callbacks (Object): Must contain "afterSave" and "afterDestroy" keys containing callback functions.

Allows the construction of arbitrary data indicies from data in your models. Indicies will stay up to date as records are created, saved or destroyed.

The afterSave and afterDestroy objects will only receive the data for a given record (generated with instance.toObject()). The afterSave callback will handle both the create and update scenarios.

Photo.addIndex('byName',{},{
    afterSave: function(index,photo){
        index[photo.name] = photo.id;
    },
    afterDestroy: function(index,photo){
        delete index[photo.name];
    }
});
var flower_record = Photo.create({name:'flower'});
Photo.indexed.byName.flower == flower_record;

If you only need and index of key => id pairs (name => id pairs in the example above), you can shorten the call to the following:

Photo.addIndex('byName','name'):

A more complicated example, which pre fills an index object:

var index = {a:{},b:{},c:{}};
 Contact.addIndex('byLetter',index,{
    afterSave: function(index,contact){
        var first_letter = contact.name.substring(0,1).toLowerCase();
        index[first_letter][contact.id] = contact;
    },
    afterDestroy: function(index,contact){
        var first_letter = contact.name.substring(0,1).toLowerCase();
        delete index[first_letter][contact.id];
    }
});
 //the index will now be available at:
Contact.indexed.byLetter;
 Contact.create({name: 'Abbey'});
 for(var id in Contact.indexed.byLetter.a){}