The binding of a bound element within an ngIf directive does not automatically update

Question

The binding of a bound element within an ngIf directive does not automatically update

I recently developed an AngularJS directive where I included an ngIf directive in the template. Within this ngIf directive, there is an input element which is bound to the scope of my directive.

<div ng-if="bool"><input ng-model="foo"></div>

After conducting numerous tests, I discovered that the model was not being updated when the text in the input field was changed due to the presence of the ngIf directive. However, when I replaced it with ngShow, everything functioned as anticipated.

I am intrigued by the reasons behind this difference and would appreciate an explanation.

Feel free to check out the jsfiddle demonstration I created here

javascript angularjs angularjs-directive

Answer 1

Answer №1

The reason for this behavior is that ngIf generates a new child scope. To bind to the same scope as the other inputs, you can use $parent to move one level down. For more information on scope inheritance, please refer to this link

  angular.module('testApp', [])
  .directive('testDir', function () {
    return {
      restrict: 'A',
      template: '<input ng-model="foo"><input ng-model="foo">' +
         '<div ng-if="bool"><input ng-model="$parent.foo"></div>',
      link: function (scope, elem, attrs) {
        scope.foo = "bar";
        scope.bool = true;       
      }
    }
  });

Check out the updated jsfiddle here

Answer 2

The reason for this behavior is that ngIf generates a new child scope. To bind to the same scope as the other inputs, you can use $parent to move one level down. For more information on scope inheritance, please refer to this link

  angular.module('testApp', [])
  .directive('testDir', function () {
    return {
      restrict: 'A',
      template: '<input ng-model="foo"><input ng-model="foo">' +
         '<div ng-if="bool"><input ng-model="$parent.foo"></div>',
      link: function (scope, elem, attrs) {
        scope.foo = "bar";
        scope.bool = true;       
      }
    }
  });

Check out the updated jsfiddle here

Answer 3

Answer №2

The reason for this issue is due to the utilization of a primitive on the scope.

When using ngIf, it generates a new child scope which then conceals the value from the parent scope.

It is recommended to utilize the dot notation instead:

<div ng-if="bool"><input ng-model="data.foo"></div>

Extracted from Insightful Scopes wiki:

Scope inheritance generally functions in a straightforward manner, often without requiring explicit awareness... until an attempt is made to implement 2-way data binding (such as form elements, ng-model) to a primitive type (e.g., number, string, boolean) defined on the parent scope within the child scope.

The expected behavior does not align with reality. In actuality, the child scope acquires its own property that masks/conceals the identically named parent property. This doesn't signify AngularJS interfering – it simply reflects the nature of JavaScript's prototypal inheritance model.

Newcomers to AngularJS frequently overlook the fact that ng-repeat, ng-switch, ng-view, and ng-include all generate distinct child scopes, often leading to complications when employing these directives.

The concern regarding primitives can be effectively circumvented by adhering to the "best practice" of consistently including a '.' in your ng-models. Watch this informative video for further guidance.

Answer 4

The reason for this issue is due to the utilization of a primitive on the scope.

When using ngIf, it generates a new child scope which then conceals the value from the parent scope.

It is recommended to utilize the dot notation instead:

<div ng-if="bool"><input ng-model="data.foo"></div>

Extracted from Insightful Scopes wiki:

Scope inheritance generally functions in a straightforward manner, often without requiring explicit awareness... until an attempt is made to implement 2-way data binding (such as form elements, ng-model) to a primitive type (e.g., number, string, boolean) defined on the parent scope within the child scope.

The expected behavior does not align with reality. In actuality, the child scope acquires its own property that masks/conceals the identically named parent property. This doesn't signify AngularJS interfering – it simply reflects the nature of JavaScript's prototypal inheritance model.

Newcomers to AngularJS frequently overlook the fact that ng-repeat, ng-switch, ng-view, and ng-include all generate distinct child scopes, often leading to complications when employing these directives.

The concern regarding primitives can be effectively circumvented by adhering to the "best practice" of consistently including a '.' in your ng-models. Watch this informative video for further guidance.

Answer 5

Answer №3

Explaining the concept of foo as an object with properties in the context of javascript prototypical inheritance. Take a look at the updated jsfiddle for more.

 angular.module('testApp', [])
  .controller('MyController',function($scope){
      $scope.foo = {bool: true};
  })
  .directive('testDir', function () {
    return {
      restrict: 'A',
      template: '<input ng-model="foo.x"><input ng-model="foo.x"><div ng-if="foo.bool"><br/>changing me does not update the other inputs because i am in an ngIf if in ngShow all works just fine<input ng-model="foo.x"></div>',
      link: function (scope, elem, attrs) {
        scope.foo.x = "bar";
        scope.foo.bool = true;       
      }
    }
  });

To delve deeper into this topic, watch this informative video.

Answer 6

Explaining the concept of foo as an object with properties in the context of javascript prototypical inheritance. Take a look at the updated jsfiddle for more.

 angular.module('testApp', [])
  .controller('MyController',function($scope){
      $scope.foo = {bool: true};
  })
  .directive('testDir', function () {
    return {
      restrict: 'A',
      template: '<input ng-model="foo.x"><input ng-model="foo.x"><div ng-if="foo.bool"><br/>changing me does not update the other inputs because i am in an ngIf if in ngShow all works just fine<input ng-model="foo.x"></div>',
      link: function (scope, elem, attrs) {
        scope.foo.x = "bar";
        scope.foo.bool = true;       
      }
    }
  });

To delve deeper into this topic, watch this informative video.

The binding of a bound element within an ngIf directive does not automatically update

Answer №1

Answer №2

It is recommended to utilize the dot notation instead:

Extracted from Insightful Scopes wiki:

Answer №3

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