Wait for data in controller before link function is run in AngularJS directive

Issue

How can I ensure that data from a controller has been loaded in a directive before the link function is run?

Using psuedo-code, I could have:

<my-map id="map-canvas" class="map-canvas"></my-map>

for my html.

In my directive I might have something like this:

app.directive('myMap', [function() {



return{
    restrict: 'AE',
    template: '<div></div>',
    replace: true,
    controller: function ($scope, PathService) {

        $scope.paths = [];

        PathService.getPaths().then(function(data){
            $scope.paths = data;

        });

    },
    link: function(scope, element, attrs){
        console.log($scope.paths.length);

    }

}


}]);

The above won't work because console.log($scope.paths.length); will get called before the service has returned any data.

I know I can call the service from the link function but would like to know if there is a way to "wait" for the service call before firing the link function.

Solution

The easiest solution would be to use ng-if since the element and directive would be rendered only when the ng-if is resolved as true

<my-map id="map-canvas" class="map-canvas" ng-if="dataHasLoaded"></my-map>

app.controller('MyCtrl', function($scope, service){
  $scope.dataHasLoaded = false;

  service.loadData().then(
    function (data) {
      //doSomethingAmazing
      $scope.dataHasLoaded = true
    }
  )
})

or use promises

return {
  restrict: 'AE',
  template: '<div></div>',
  replace: true,
  controller: function ($scope, PathService) {
    $scope.paths = [];
    $scope.servicePromise = PathService.getPaths()
  },
  link: function (scope, element, attrs) {
    scope.servicePromise.then(function (data) {
      scope.paths = data;
      console.log(scope.paths)
    });
  }
}

Answered By - maurycy