vm.Something = new Something();

some-factory.js

angular.module('SomeApp').factory('SomeFactory',
    function ($rootScope) {
        var Something = function () {
            this.Stuff = [];
            this.AlertStuffLength = function () {
                alert("This much Stuff: " + this.Stuff.length);
            }
            this.AddStuff = function (_stuff) {
                this.Stuff.push(_stuff);
            }
            return this;
        };

        return Something;
    });


/*  
//implementation in some-controller
vm.Something = new Something();
vm.ClickShowStuff = function(){ vm.Something.AlertStuffLength();};
vm.AddStuff = function(){ vm.Something.AddStuff(vm.StuffName)};
// end some-controller
*/