Callback function located within directive attribute specified in separate attribute

Question

Callback function located within directive attribute specified in separate attribute

Recently, I created a directive called mySave, and it looks like this:

app.directive('mySave', function($http) {
   return function(scope, element, attrs) {
      element.bind("click", function() {
          $http.post('/save', scope.data).success(returnedData) {
              // callback defined on my utils service here

              // user defined callback here, from my-save-callback perhaps?
          }
      });
   }
});

Here is how the element using this directive looks:

<button my-save my-save-callback="callbackFunctionInController()">save</button>

The current implementation of the callbackFunctionInController in the controller is pretty basic:

$scope.callbackFunctionInController = function() {
    alert("callback");
}

However, when I try to console.log() attrs.mySaveCallback within the my-save directive, it returns a string value of callbackFunctionInController(). After reading some information suggesting that I should use $parse on this, I attempted to do so by calling $parse(attrs.mySaveCallback). This resulted in receiving a different function than expected:

function (a,b){return m(a,b)}

I'm unsure of what I'm doing wrong in this process. Is this approach possibly flawed from the beginning?

javascript ajax angularjs angularjs-directive

Answer 1

Answer №1

One effective approach is to utilize the isolated scope recommendation by ProLoser

app.directive('mySubmit', function($http) {
   return {
      scope: {
        action: '&mySubmitAction'
      }
      link: function(scope, element, attrs) {
        element.on("click", function() {
            $http.post('/submit', scope.$parent.data).success(returnedData) {
                // calling the callback function from my utility service

                scope.action(); // triggers an alert
            }
        });
      }
   }
});

To send parameters back to the controller, follow these steps

[11:28] <revolunet> you need to pass named variables 
[11:28] <revolunet> for instance, my-var="action(a, b)" 
[11:29] <revolunet> in the directive: scope.action({a:xxx, b:yyy})

Answer 2

One effective approach is to utilize the isolated scope recommendation by ProLoser

app.directive('mySubmit', function($http) {
   return {
      scope: {
        action: '&mySubmitAction'
      }
      link: function(scope, element, attrs) {
        element.on("click", function() {
            $http.post('/submit', scope.$parent.data).success(returnedData) {
                // calling the callback function from my utility service

                scope.action(); // triggers an alert
            }
        });
      }
   }
});

To send parameters back to the controller, follow these steps

[11:28] <revolunet> you need to pass named variables 
[11:28] <revolunet> for instance, my-var="action(a, b)" 
[11:29] <revolunet> in the directive: scope.action({a:xxx, b:yyy})

Answer 3

Answer №2

There are numerous approaches to tackle the task at hand. The FIRST crucial point to understand is that the $http.post() function will be triggered as soon as the DOM element is rendered by the template engine, and that's it. Placing it within a repeat loop will result in the function being executed for each new item in the repeater, which may not align with your objectives. If it does, then there might be a flaw in the design logic because the presence of DOM elements alone should not drive backend calls.

To address your query directly; after reading through the somewhat inadequate documentation on $parse, you'll discover that it provides an evaluation expression. By invoking this function and passing the scope to evaluate, you will obtain the current state of that expression on the passed scope, effectively executing your function.

var expression = $parse(attrs.mySave);
results = expression($scope); // call when necessary
expression.assign($scope, 'newValue'); // primary use of $parse, assigning values

Admittedly, it may seem perplexing initially, but it's important to grasp that a $scope undergoes constant changes in asynchronous applications, emphasizing the timing of value determination rather than just the method. $parse proves valuable for referencing a model to which you can assign a value, not solely for reading from it.

It would also be beneficial to delve into creating an isolate scope or mastering how to $eval() an expression.

$scope.$eval(attrs.mySave);

Answer 4

There are numerous approaches to tackle the task at hand. The FIRST crucial point to understand is that the $http.post() function will be triggered as soon as the DOM element is rendered by the template engine, and that's it. Placing it within a repeat loop will result in the function being executed for each new item in the repeater, which may not align with your objectives. If it does, then there might be a flaw in the design logic because the presence of DOM elements alone should not drive backend calls.

To address your query directly; after reading through the somewhat inadequate documentation on $parse, you'll discover that it provides an evaluation expression. By invoking this function and passing the scope to evaluate, you will obtain the current state of that expression on the passed scope, effectively executing your function.

var expression = $parse(attrs.mySave);
results = expression($scope); // call when necessary
expression.assign($scope, 'newValue'); // primary use of $parse, assigning values

Admittedly, it may seem perplexing initially, but it's important to grasp that a $scope undergoes constant changes in asynchronous applications, emphasizing the timing of value determination rather than just the method. $parse proves valuable for referencing a model to which you can assign a value, not solely for reading from it.

It would also be beneficial to delve into creating an isolate scope or mastering how to $eval() an expression.

$scope.$eval(attrs.mySave);

Answer 5

Answer №3

Utilize .$eval to run a statement within the specified scope

app.directive('mySave', function($http) {
   return function(scope, element, attrs) {
      $http.post('/save', scope.data).success(returnedData) {
          // callback defined on my utils service here

          // user defined callback here, from my-save-callback perhaps?
          scope.$eval(attrs.mySaveCallback)
      }
   }
});

TD: Demo

If you wish to exchange data between a directive and a controller, you can utilize two-way binding

app.controller('AppController', function ($scope) {
   $scope.callbackFunctionInController = function() {
      console.log('do something')
   };

   $scope.$watch('somedata', function(data) {
      console.log('controller', data);
   }, true);
});

app.directive('mySave', function($http, $parse) {
   return {
     scope: {
       data: '=mySaveData',
       callback: '&mySaveCallback' //the callback
     },
     link: function(scope, element, attrs) {
       $http.get('data.json').success(function(data) {
         console.log('data', data);
         scope.data = data;
         scope.callback(); //calling callback, this may not be required
       });
     }
   };
});

Demo: Fiddle

Answer 6

Utilize .$eval to run a statement within the specified scope

app.directive('mySave', function($http) {
   return function(scope, element, attrs) {
      $http.post('/save', scope.data).success(returnedData) {
          // callback defined on my utils service here

          // user defined callback here, from my-save-callback perhaps?
          scope.$eval(attrs.mySaveCallback)
      }
   }
});

TD: Demo

If you wish to exchange data between a directive and a controller, you can utilize two-way binding

app.controller('AppController', function ($scope) {
   $scope.callbackFunctionInController = function() {
      console.log('do something')
   };

   $scope.$watch('somedata', function(data) {
      console.log('controller', data);
   }, true);
});

app.directive('mySave', function($http, $parse) {
   return {
     scope: {
       data: '=mySaveData',
       callback: '&mySaveCallback' //the callback
     },
     link: function(scope, element, attrs) {
       $http.get('data.json').success(function(data) {
         console.log('data', data);
         scope.data = data;
         scope.callback(); //calling callback, this may not be required
       });
     }
   };
});

Demo: Fiddle

Answer 7

Answer №4

context: {
    handler: '&mySaveHandler'
}

Explicitly defining the context can be a helpful solution, but it may limit access to other parts of the original context. In my case, I needed to access other parts of the context beyond what was defined. To achieve this, I followed a similar approach to ng-click's implementation.

Here is an example of how I used my directive in HTML:

<div my-custom-directive source="dataSrc" action="performAction(data)">

Within the directive (without explicitly setting the context):

var actionPerformed = $parse(attrs.action);
    context.$apply(function () {
    actionPerformed( {data : conditions}, context, { $event: event });
});

Using this method allows me to call the function in the controller and provide parameters for it.

In the controller:

$scope.performAction= function(data){
    console.log(data);
}

This will correctly display the conditions passed to it.

Answer 8

context: {
    handler: '&mySaveHandler'
}

Explicitly defining the context can be a helpful solution, but it may limit access to other parts of the original context. In my case, I needed to access other parts of the context beyond what was defined. To achieve this, I followed a similar approach to ng-click's implementation.

Here is an example of how I used my directive in HTML:

<div my-custom-directive source="dataSrc" action="performAction(data)">

Within the directive (without explicitly setting the context):

var actionPerformed = $parse(attrs.action);
    context.$apply(function () {
    actionPerformed( {data : conditions}, context, { $event: event });
});

Using this method allows me to call the function in the controller and provide parameters for it.

In the controller:

$scope.performAction= function(data){
    console.log(data);
}

This will correctly display the conditions passed to it.

Answer 9

Answer №5

It was successful for me

Within the view script

<tag mycallbackattrib="scopemethod">

Inside the directive

$scope[attrs.mycallbackattrib](params....);

The function is executed correctly and parameters are passed, although it may not be the most efficient way to work with Angular.

Answer 10

It was successful for me

Within the view script

<tag mycallbackattrib="scopemethod">

Inside the directive

$scope[attrs.mycallbackattrib](params....);

The function is executed correctly and parameters are passed, although it may not be the most efficient way to work with Angular.

Answer 11

Answer №6

It is recommended to utilize the ng-click attribute rather than developing a custom directive.

Answer 12

It is recommended to utilize the ng-click attribute rather than developing a custom directive.

Answer 13

Answer №7

app.directive('mySave', function($http, $parse) {
   return {
     scope: {
       data: '=mySaveData',
       callback: '&' //this is the defined callback function
     },
     link: function(scope, element, attrs) {
       $http.get('data.json').success(function(data) {
         console.log('Retrieved data:', data);
         if (scope.callback()) scope.callback().apply(data);
       });
     }
   };
});

Answer 14

app.directive('mySave', function($http, $parse) {
   return {
     scope: {
       data: '=mySaveData',
       callback: '&' //this is the defined callback function
     },
     link: function(scope, element, attrs) {
       $http.get('data.json').success(function(data) {
         console.log('Retrieved data:', data);
         if (scope.callback()) scope.callback().apply(data);
       });
     }
   };
});

Callback function located within directive attribute specified in separate attribute

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

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