You can use services to achieve this objective.
As you have two different apps and you need to create a bridge between them, a good way is to create services that can be injected where you need them.
A AngularJs service is created inside an AngularJs App, by declaring it using your angular module like this:
angular.module("YourAngularModuleName").factory("MyCustomService",
[
"injectedDependency",
function(injectedDependency)
{
var serviceInstance={};
serviceInstance.operationYouNeed = function(){
//do your stuff.
return;
};
return serviceInstance;
}
]);
This service above is a example structure of a service called "MyCustomService" that has a method called "operationYouNeed".
On your AngularJs App controller, you can inject your MyCustomService and call operationYouNeed as you may need it.
Considering the scenario you exposed, I don't know the way you are keeping the logged user context, but you can evaluate the user action on the service method and then call a $location.path("your app2 root url") in order to redirect the user or, if is the case, call a $window.location.href = "your app2 root url" in order to cause a page reload.
In applications that I write, I use to implement a token based authentication and store the temporary toke as a private cookie, so if I had your app scenario, on App2 I would inject $cookies on my Service and use it to retrieve the temporary cookie in order to check session validation and also decide if I need to redirect my user or not.
Another kind of concept you can implement here is to use a third AngularJs app in which you declare your common service, so you don't need to create any dangerous circular reference between your two apps.
I don't know the deepnes of your AngularJs knowledge but you allways need to declare a module dependency whe you does something like this, by including it on your AngularJs app module, like so:
angular.module("YourAngularModuleName",["anotherDepencyModule", "another", ...]);
Hope it helps.
Cheers.
