Angular UI-Router：$ state.current有时是未定义的

Question

I'm using ui.router in my angular app, and in my navbar controller (which is included in more than one template) I wrote a simple console.log($state.current) to test it's behavior.

I've noticed that, sometimes, upon reload, the state is undefined:

Object {name: "", url: "^", views: null, abstract: true}

and sometimes it is defined:

Object {url: "/admin", templateUrl: "app/components/admin-dashboard/admin-dashboard.html", controller: "AdminCtrl", controllerAs: "vm", name: "admin-dashboard"}

What might be the cause of this behavior and how can I guarantee that my state is defined when the view is loaded?

Answer 1

Surest way to get the right value in $state.current is to wait for the $stateChangeSuccess event to be fired by ui-router. Here's how you can do it:

In your Navbar controller:

$rootScope.$on('$stateChangeSuccess', 
function(event, toState, toParams, fromState, fromParams){ 
    event.preventDefault(); 
    console.log($state.current)  // this should now always have a resolved value
})

Refer ui-router wiki for more details.

Why this works as against only doing a console.log($state.current) is because, $state.current has the right value only 'after' the route is fully loaded. When you write it without the event, depending on where you write it, it can be a hit or miss. That's why you were getting inconsistent results. It's exactly for this reason that ui-router provides a success event, which promises that route has definitely been resolved.