javascript - Angularjs undefined object when attribute two-way binding -

i running problem i'm trying in angularjs. thing goes this:

i have controller , have directive defined this:

helpers.directive('someevent', function() {      ...     scope: {        api: '='     }     ...     controller: ['$scope', function($scope) {          $scope.hassomeeventoccured = function(){              return booleanvariable         };          $scope.api = {            hassomeeventoccured: $scope.hassomeeventoccured        }     }]  }); 

then, in other controller want access function hassomeeventoccured... controller defined follows:

modulename.controller('modulesomethingcontroller', ['$scope', '$state', 'modulerepository', function ($scope, $state, modulerepository) {      $scope.theeventoccured = $scope.someeventapi.hassomeeventoccured();  }]); 

and in cshtml file have:

<some-event api="someeventapi" ></some-event>  <div ng-if="theeventoccured"></div> 

the error occurs $scope.someeventapi undefined. , line breaks: $scope.theeventoccured = $scope.someeventapi.hassomeeventoccured(); assume happens because call hassomeeventoccured within modulesomethingcontroller occurs before binding someevent completed.

my question how solve problem?

i aware in directive have like:

link: function(scope, element, attrs) {    attrs.$observe(...); } 

but how can achieve wait binding complete in situation?

so- reason "$scope.someeventapi undefined" error, because didn't set anywhere. undefined! use inside controller should either defined (var x = something...) or injected (just injected $scope in example)

the way see it, have 2 options want:

1. a common , straightforward way define function inside the controller , send function directive. means you'll need add directive definition that:

scope: {theeventoccured: '&' }

the & sign means it's function.

inside controller:

$scope.theeventoccured = function() { /* code here */ } 

this way- api defined inside controller, , directive uses when needed.

1. for more complex stuff- can create .factory , bind controller , directive.

2. if trying communicate between different controllers (or controllers of directive) can either use factory or $broadcast event. see $broadcast , $emit in the scope api

two other important things: not supposed use directive's function in it's parent controller scope if understand want achieve, not need $observe here.