$rootScope
basically functions as an event listener and dispatcher.
To answer the question of how it is used, it used in conjunction with rootScope.$on
;
$rootScope.$broadcast("hi");
$rootScope.$on("hi", function(){
//do something
});
However, it is a bad practice to use $rootScope
as your own app’s general event service, since you will quickly end up in a situation where every app depends on $rootScope, and you do not know what components are listening to what events.
The best practice is to create a service for each custom event you want to listen to or broadcast.
.service("hiEventService",function($rootScope) {
this.broadcast = function() {$rootScope.$broadcast("hi")}
this.listen = function(callback) {$rootScope.$on("hi",callback)}
})