Ui-router: how to block url navigation but accept state navigation - angularjs

Question

I try to do some functionality that accepts a state navigation (using $state.go(otherState)), refreshing the associated url in the adress/url bar but it blocks (or redirects to not allowed page) if user directly puts this url in the adress/url bar.
Could it be done by ui-router rules or something inside ui-router module?
I put the example code:
$stateProvider.state("main", {
url: "/index.html",
templateUrl: "main.html"
}).state("notAccessibleScreenByBar", {
url: "/private/example.html",
templateUrl: "example.html"
});
From main view (index.html), the next angular code will be executed:
$state.go("notAccessibleScreenByBar");
This action changes the view, loading example.html and refreshing the url bar to /private/example.html.
If user puts /private/example.html in the adress/url bar, ui-router must block this request (or redirect to not-allowed page).

Answer 1

What you are trying to do seems very similar to any web authentication standard, but, if you don't want that, you could use $locationChangeSuccess (docs here)
A basic example inspired by this sample:
$rootScope.$on('$locationChangeSuccess', function(e, newUrl, oldUrl) {
// Prevent $urlRouter's default handler from firing
e.preventDefault();
if(isThisTransitionValid(newUrl, oldUrl)) {
// Ok, let's go
$urlRouter.sync();
});
});