Achieving two-way data binding in a directive without using an isolated scope

Question

Achieving two-way data binding in a directive without using an isolated scope

Implementing scope: { ... } in a directive creates an isolated scope that doesn't inherit from its parent. However, my usual practice has been to utilize this for easily declaring HTML attributes with bi-directional data binding:

scope: {
    attr1: '=',
    attr2: '?='
}

If you want a non-isolated scope, you must use scope: true, but this method doesn't allow the declaration of such attributes. Now, I find myself needing a directive with a non-isolated scope that still enables two-way binding. What's the most effective way to accomplish this?

For example, consider the scenario below within the outer-directive's view:

<div ng-repeat="e in element">
    <inner-directive two-way-attr="e.value"></inner-directive>
</div>

Despite being part of the same module as outer-directive, inner-directive doesn't require encapsulation with an isolated scope. In reality, I rely on $scope inheritance for other purposes so isolating the scope isn't viable. Nonetheless, utilizing an HTML attribute for establishing this two-way communication proves to be highly convenient.

javascript angularjs angularjs-directive angularjs-scope

Answer 1

Answer №1

Pixelbits really came through for me in helping solve this issue, although their answer initially seemed overly complex. Upon further investigation, I discovered that the solution is actually quite straightforward.

Consider a directive with an isolate scope like the one below:

scope: { model: '=myModel' },
link: function(scope, element, attr) {
    //...
}

The following code achieves the same result, but without an isolate scope:

scope: true,
link: function(scope, element, attr) {
    scope.model = scope.$parent.$eval(attr.myModel);
    //...
}

For a demonstration, check out this live example: http://jsfiddle.net/mhelvens/SZ55R/1/

Answer 2

Pixelbits really came through for me in helping solve this issue, although their answer initially seemed overly complex. Upon further investigation, I discovered that the solution is actually quite straightforward.

Consider a directive with an isolate scope like the one below:

scope: { model: '=myModel' },
link: function(scope, element, attr) {
    //...
}

The following code achieves the same result, but without an isolate scope:

scope: true,
link: function(scope, element, attr) {
    scope.model = scope.$parent.$eval(attr.myModel);
    //...
}

For a demonstration, check out this live example: http://jsfiddle.net/mhelvens/SZ55R/1/

Answer 3

Answer №2

Check Out the Live Demo Here

Did you know that it is actually possible to have both an isolate scope and a non-isolate scope within the same directive? This can be useful when you have a combination of templates that should either inherit bindings from their parent scopes or have their own isolated bindings.

If you want to set up both types of scopes in your directive, here's how you can do it:

In your directive definition, make sure to specify scope=true
Within your link function, compile and link your template against the scope parameter. This will allow the bindings to be resolved through prototypical scope inheritance.
```
  link: function(scope, element, attr) {

    // This template will use prototypical scope inheritance to look for 'model'
    var template2 = angular.element('<div> Prototypical Scope: {{ model }}</div>');

    // Add the template to the DOM
    element.append(template2);

    // Compile and link the template against the prototypical scope
    $compile(template2)(scope);
  }
```
The benefit of using prototypical scope inheritance is that you don't need to explicitly import bindings into your current scope. As long as a binding is defined in the current scope or any ancestor scope (all the way up to the root scope), Angular can resolve it.

Within the same link function, you can also define an isolated scope using scope.$new(true). You can establish a two-way binding for your model by importing it into the isolated scope -

isolatedScope.model = scope.$eval(attr.model)

:

 link: function(scope, element, attr) {

    // This template will only look for 'model' in the current isolated scope
    var template = angular.element('<div> Isolate Scope: {{model}}</div>');

    // Create an isolated scope
    var isolatedScope = scope.$new(true);

    // Import the model from the parent scope into the isolated scope to create a two-way binding           
    isolatedScope.model = scope.$eval(attr.model);

    // Add the template to the DOM
    element.append(template);

    // Compile and link the template against the isolated scope
    $compile(template)(isolatedScope);

}

The advantage of using an isolate scope is that you only import the bindings that are explicitly needed. In contrast, with a non-isolate scope, the bindings can be inherited from any higher scope in the hierarchy without needing to be defined on the current scope.

Answer 4

Check Out the Live Demo Here

Did you know that it is actually possible to have both an isolate scope and a non-isolate scope within the same directive? This can be useful when you have a combination of templates that should either inherit bindings from their parent scopes or have their own isolated bindings.

If you want to set up both types of scopes in your directive, here's how you can do it:

In your directive definition, make sure to specify scope=true
Within your link function, compile and link your template against the scope parameter. This will allow the bindings to be resolved through prototypical scope inheritance.
```
  link: function(scope, element, attr) {

    // This template will use prototypical scope inheritance to look for 'model'
    var template2 = angular.element('<div> Prototypical Scope: {{ model }}</div>');

    // Add the template to the DOM
    element.append(template2);

    // Compile and link the template against the prototypical scope
    $compile(template2)(scope);
  }
```
The benefit of using prototypical scope inheritance is that you don't need to explicitly import bindings into your current scope. As long as a binding is defined in the current scope or any ancestor scope (all the way up to the root scope), Angular can resolve it.

Within the same link function, you can also define an isolated scope using scope.$new(true). You can establish a two-way binding for your model by importing it into the isolated scope -

isolatedScope.model = scope.$eval(attr.model)

:

 link: function(scope, element, attr) {

    // This template will only look for 'model' in the current isolated scope
    var template = angular.element('<div> Isolate Scope: {{model}}</div>');

    // Create an isolated scope
    var isolatedScope = scope.$new(true);

    // Import the model from the parent scope into the isolated scope to create a two-way binding           
    isolatedScope.model = scope.$eval(attr.model);

    // Add the template to the DOM
    element.append(template);

    // Compile and link the template against the isolated scope
    $compile(template)(isolatedScope);

}

The advantage of using an isolate scope is that you only import the bindings that are explicitly needed. In contrast, with a non-isolate scope, the bindings can be inherited from any higher scope in the hierarchy without needing to be defined on the current scope.

Answer 5

Answer №3

This content was authored by me and can be utilized in the following manner:

twowaybinder.attach($scope, $attrs.isDeactivated, 'isDeactivated');

.factory('twowaybinder', function ($parse) {
  function establishTwoWayBinding($scope, external, internal){
    var remoteSetter = $parse(external).assign;
    var localSetter = $parse(internal).assign;

    $scope.$parent.$watch(external, function (value) {
      localSetter($scope, value);
    });

    $scope.$watch(internal, function (value) {
      remoteSetter($scope, value);
    });
  }

  return {
    attach : establishTwoWayBinding
  };
});

This implementation enables genuine two-way binding between scope values. I believe that utilizing $scope.$parent may not be necessary, since in cases of inherited or no scope, any expression should resolve on the current scope. The use of $parent would only be required in instances of an isolated scope, in which case this approach would not be applicable; instead, the isolated scope configuration would be employed.

Answer 6

This content was authored by me and can be utilized in the following manner:

twowaybinder.attach($scope, $attrs.isDeactivated, 'isDeactivated');

.factory('twowaybinder', function ($parse) {
  function establishTwoWayBinding($scope, external, internal){
    var remoteSetter = $parse(external).assign;
    var localSetter = $parse(internal).assign;

    $scope.$parent.$watch(external, function (value) {
      localSetter($scope, value);
    });

    $scope.$watch(internal, function (value) {
      remoteSetter($scope, value);
    });
  }

  return {
    attach : establishTwoWayBinding
  };
});

This implementation enables genuine two-way binding between scope values. I believe that utilizing $scope.$parent may not be necessary, since in cases of inherited or no scope, any expression should resolve on the current scope. The use of $parent would only be required in instances of an isolated scope, in which case this approach would not be applicable; instead, the isolated scope configuration would be employed.

Answer 7

Answer №4

When working with AngularJS, you have the option to utilize two directives in your code. If 'gg' is considered an object, then "=" allows you to reference a specific location in memory!

angular.module('mymodule', []).directive('a', function($parse, $modal) {
return {
    restrict : 'A',
    scope : {
        gg : "="
    },
    require : "b",
    link : function(scope, element, attrs, bCtrl) {
        scope.$watch('gg',function(gg){
            bCtrl.setset(scope.gg);
        }
    }
}
});

angular.module('mymodule').directive('b', function($parse, $modal) {

return {
    restrict : 'A',
    /*
     * scope : { showWarn : "=" },
     */
    controller : function($scope) {
        $scope.bb = {};

        this.setset = function(nn) {

            $scope.bb=nn;
        };

    }
});

Answer 8

When working with AngularJS, you have the option to utilize two directives in your code. If 'gg' is considered an object, then "=" allows you to reference a specific location in memory!

angular.module('mymodule', []).directive('a', function($parse, $modal) {
return {
    restrict : 'A',
    scope : {
        gg : "="
    },
    require : "b",
    link : function(scope, element, attrs, bCtrl) {
        scope.$watch('gg',function(gg){
            bCtrl.setset(scope.gg);
        }
    }
}
});

angular.module('mymodule').directive('b', function($parse, $modal) {

return {
    restrict : 'A',
    /*
     * scope : { showWarn : "=" },
     */
    controller : function($scope) {
        $scope.bb = {};

        this.setset = function(nn) {

            $scope.bb=nn;
        };

    }
});

Achieving two-way data binding in a directive without using an isolated scope

Answer №1

Answer №2

Answer №3

Answer №4

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