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JavaScript AngularJS Extending Inputs Extending Inputs: Optional require

Posted by Branko Dragovic
Branko Dragovic
26,314 Points

check is controller defined

can somebody help me with this task please? I dont get it :/

app.js 
angular.module('treehouseCourse', [])
  .directive('sometimesTwoWay', function() {
    return {
      // YOUR CODE HERE
      require: '?ngModel',
      link: function($scope,$element,$attrs,ngModelCtrl){}
    }
  });
index.html 
<!DOCTYPE html>
<html ng-app="treehouseCourse">
<head>
  <title>Angular.js</title>
  <script src="js/angular.js"></script>
  <script src="app.js"></script>
</head>
<body>

  <sometimes-two-way ng-model="course.description"></sometimes-two-way>

</body>
</html>

2 Answers

Iain Simmons
MOD
Iain Simmons
Treehouse Moderator 32,305 Points
Iain Simmons
Iain Simmons
Treehouse Moderator 32,305 Points

The controller should be the value passed to the parameter ngModelCtrl in the link function. It will either be defined (passed a value) or by default, will be undefined, as any parameter not passed into a function would be in JavaScript.

So you're essentially testing if ngModelCtrl equals undefined.

The simplest way to do that is a conditional with a logical NOT operator:

if (!ngModelCtrl) {
  // ngModelCtrl is undefined
}

OR of course, you can leave out the ! and check first to see if it is defined:

if (ngModelCtrl) {
  // ngModelCtrl is defined
} else {
  // ngModelCtrl is undefined
}

Hope that helps!

Branko Dragovic
Branko Dragovic
26,314 Points
Branko Dragovic
Branko Dragovic
26,314 Points

Thank you Iain :)

Iain Simmons
Iain Simmons
Treehouse Moderator 32,305 Points

No problem. You should probably mark the answer as 'Best Answer' if it answered your question, that way other students know your question has been answered/closed.