value assigned to ng-model does not update beyond its scope

Question

value assigned to ng-model does not update beyond its scope

My issue involves binding an ng-model to an input field. Despite this, the value of the variable it is connected to does not update outside of the specific div where the directive is defined:

<div input-field
     ng-if="startTypes.selected.value == 'LocalDate' || startTypes.selected.value == 'LocalDateTime'">
  <input id="date" type="text" ng-model="date" input-date>
  <label for="date">Date</label>
  Date within scope: {{date}}
</div>
Date outside of scope: {{date}}

Each time a new date is selected, only the inner date is updated. The outer one retains its previous value (which may be either undefined or not depending on whether it was declared in the controller).

I am utilizing angular-materialize, but I am uncertain if this is causing the problem as it is specifically designed for Angular integration with the CSS framework materializecss.

Here is the component I am employing.

Edit:

Attempted declaring date in the controller using $scope.date = new Date(). This indeed loads the current date in the date picker. However, upon selecting a date and changing the model, the update remains localized (inner scope) while the outer scope retains the old value.

javascript angularjs angularjs-forms

Answer 1

Answer №1

When using ng-if, a child scope is created which inherits properties from the current scope when inserting inner templates into the DOM. This results in ng-model being created inside the child scope of ng-if. As a result, primitive data types and object references are passed to the child scope. This explains why the outer scope's value for date appears in the ng-if date field initially. However, if you update the value of date, it will not reflect back in the outer scope because primitive values do not carry their references to child scopes, unlike objects which do. To solve this issue, create an object like $scope.model = {} and define properties within it, as objects retain their references in child scopes. Following the 'Dot Rule' by manipulating the inner object will also update the outer object accordingly.

$scope.model = {};
$scope.model.date = new Date();

To avoid such nested scope issues, consider employing the controllerAs pattern when defining controllers in HTML. By binding all properties to the controller function's context (this) instead of using $scope, you can access these properties using an alias when referring to the controller in the HTML template, like ng-controller="myCtrl as vm" (where vm represents the controller instance with all properties bound to this).

HTML

<div input-field
     ng-if="vm.startTypes.selected.value == 'LocalDate' || vm.startTypes.selected.value == 'LocalDateTime'">
  <input id="date" type="text" ng-model="vm.date" input-date>
  <label for="date">Date</label>
  Date inner scope: {{vm.date}}
</div>
Date outer scope: {{vm.date}}

Answer 2

When using ng-if, a child scope is created which inherits properties from the current scope when inserting inner templates into the DOM. This results in ng-model being created inside the child scope of ng-if. As a result, primitive data types and object references are passed to the child scope. This explains why the outer scope's value for date appears in the ng-if date field initially. However, if you update the value of date, it will not reflect back in the outer scope because primitive values do not carry their references to child scopes, unlike objects which do. To solve this issue, create an object like $scope.model = {} and define properties within it, as objects retain their references in child scopes. Following the 'Dot Rule' by manipulating the inner object will also update the outer object accordingly.

$scope.model = {};
$scope.model.date = new Date();

To avoid such nested scope issues, consider employing the controllerAs pattern when defining controllers in HTML. By binding all properties to the controller function's context (this) instead of using $scope, you can access these properties using an alias when referring to the controller in the HTML template, like ng-controller="myCtrl as vm" (where vm represents the controller instance with all properties bound to this).

HTML

<div input-field
     ng-if="vm.startTypes.selected.value == 'LocalDate' || vm.startTypes.selected.value == 'LocalDateTime'">
  <input id="date" type="text" ng-model="vm.date" input-date>
  <label for="date">Date</label>
  Date inner scope: {{vm.date}}
</div>
Date outer scope: {{vm.date}}

Answer 3

Answer №2

It is recommended to utilize an object containing a property when connecting to ngModel.

$scope.userData = {
   email: "example@gmail.com"
};

Answer 4

It is recommended to utilize an object containing a property when connecting to ngModel.

$scope.userData = {
   email: "example@gmail.com"
};

Answer 5

Answer №3

The ngIf directive, similar to the ngRepeat directive, generates its own $scope.

Therefore, in this particular scenario, you can opt for using ng-show instead of ng-if.

According to the documentation:

The ngIf directive either removes or recreates a segment of the DOM tree depending on an {expression}. If the expression assigned to ngIf is assessed as false, the element is deleted from the DOM; otherwise, a duplicate of the element is inserted back into the DOM.

For instance:

angular.module('app', [])
  .controller('mainCtrl', function($scope) {
    $scope.testa = false;
    $scope.testb = false;
    $scope.testc = false;
    $scope.testd = false;
  });

<!DOCTYPE html>
<html ng-app="app">

<head>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.5.7/angular.min.js"></script>
</head>

<body ng-controller="mainCtrl">
  Test A: {{testa}}
  <br /> Test B: {{testb}}
  <br /> Test C: {{testc}}
  <br /> Test D: {{testd}}
  <br />

  <div>
    testa (without ng-if):
    <input type="checkbox" ng-model="testa" />
  </div>
  <div ng-if="!testa">
    testb (with ng-if):
    <!-- if you don't use $parent testb isn't updated -->
    <input type="checkbox" ng-model="$parent.testb" />
  </div>
  <div ng-show="!testa">
    testc (with ng-show):
    <input type="checkbox" ng-model="testc" />
  </div>
  <div ng-hide="testa">
    testd (with ng-hide):
    <input type="checkbox" ng-model="testd" />
  </div>
</body>

</html>

Answer 6

The ngIf directive, similar to the ngRepeat directive, generates its own $scope.

Therefore, in this particular scenario, you can opt for using ng-show instead of ng-if.

According to the documentation:

The ngIf directive either removes or recreates a segment of the DOM tree depending on an {expression}. If the expression assigned to ngIf is assessed as false, the element is deleted from the DOM; otherwise, a duplicate of the element is inserted back into the DOM.

For instance:

angular.module('app', [])
  .controller('mainCtrl', function($scope) {
    $scope.testa = false;
    $scope.testb = false;
    $scope.testc = false;
    $scope.testd = false;
  });

<!DOCTYPE html>
<html ng-app="app">

<head>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.5.7/angular.min.js"></script>
</head>

<body ng-controller="mainCtrl">
  Test A: {{testa}}
  <br /> Test B: {{testb}}
  <br /> Test C: {{testc}}
  <br /> Test D: {{testd}}
  <br />

  <div>
    testa (without ng-if):
    <input type="checkbox" ng-model="testa" />
  </div>
  <div ng-if="!testa">
    testb (with ng-if):
    <!-- if you don't use $parent testb isn't updated -->
    <input type="checkbox" ng-model="$parent.testb" />
  </div>
  <div ng-show="!testa">
    testc (with ng-show):
    <input type="checkbox" ng-model="testc" />
  </div>
  <div ng-hide="testa">
    testd (with ng-hide):
    <input type="checkbox" ng-model="testd" />
  </div>
</body>

</html>

value assigned to ng-model does not update beyond its scope

Answer №1

Answer №2

Answer №3

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