angularjs - Angular states - resolve before exiting -

my angular app includes main screen , several tabs , i'm using $stateprovider switch between states. whenever i'm leaving tab (=state) must perform asynchronous operation. wait operation complete before moving new tab. resolve done when leaving state rather entering.

how can achieved?

example snippet:

$stateprovider     .state('myproject.main', {         url: '/main',         templateurl: '...',         controller: 'mainctrl'     })     .state('myproject.tabs.a', {         url: '/tab_a',         controller: 'tabactrl',         templateurl: '...',         onexit: dosave     })     .state('myproject.tabs.b', {         url: '/tab_b',         controller: 'tabbctrl',         templateurl: '...',         onexit: dosave     });  function dosave(myservice) {     return myservice.save(); //async, promise } 

here wanted save (async) whenever switching between tabs. when entering main state tab, want sure save has finished (doing save on myproject.main's onenter/resolve not me).

problem: when entering myproject.main (mainctrl), async myservice.save() operation still processing. want completed/resolved.

i tried hack following piece of code, does not work - state change enters loop

.run(function($rootscope, $state, $stateparams, myservice){     $rootscope.$on('$statechangestart', function(ev, tostate, toparams, fromstate, fromparams){         if (tostate.name === 'myproject.main' && //switching main             fromstate.name && //for tab             fromparams.resume !== true ) {                ev.preventdefault(); //stop state change               //do save , continue state change               myservice.save().then(function(){                 $state.go(tostate, {resume: true}) //continue "resume" parameter               });         }     });              }); 

thanks!