Ways to guarantee that the factory promise is fulfilled prior to the execution of the

Question

Ways to guarantee that the factory promise is fulfilled prior to the execution of the

So far, I have always found valuable help by studying existing answers on stackoverflow, but now I've hit a roadblock.

I'm currently working on an app that utilizes a directive to generate calendar month boxes.

<app2directive class="column_50" year="2016" month="November"></app2directive>

The directive code isolates the scope and uses a templateUrl file to display the calendar month.

App.directive('app2directive',function( YEARS, MONTHS, DAYS){

return {
    restrict:"ACE",
    scope:{},
    replace:true,
    templateUrl:"templates/cal_directive3.html",
    controller: function ( $scope, $attrs, $injector, $log, YEARS, MONTHS, DAYS) {            var factoryName = "datumFactory" ;
        var factoryTonnen = "jsonsrc" ;
        var factoryInstance = $injector.get( factoryName ) ;
        var tonnenInstance = $injector.get( factoryTonnen ) ;

        var wtf = $scope.jsondata.get().then( function( promise){
            console.log( "jsondata", promise ) ;
            //$scope.tonnen = promise ;
        }, function( error){
            console.log( "error", error ) ;
        }) ;


});

Currently, I am using an $injector to inject a factory that performs a $http request to retrieve data from a JSON file containing information like holidays or other static details specific to the chosen year and month(s).

App.factory( 'jsonsrc', function( $http, $q ){ 
return {
    get: function(){
        var deferred = $q.defer() ;
        $http.get( 'termine_2016.json' )
            .success(function(data, status, headers, config) {
                deferred.resolve( data ) ;
            }).error(function(data, status, headers, config) {
                console.log( "[jsonsrc] request did not work!" );
                deferred.reject( data ) ;
            }) ;
        return deferred.promise ;
    }
}

});

This results in the $http call being made 12 times for a full year page load.

My goal is to refactor the code so that I can ideally load the JSON data into the main controller and have the directive inherit from the parent scope.

Since the call returns a promise, the directive needs to wait for it to resolve before proceeding, but I am currently unsure how to approach this. Any guidance would be greatly appreciated!

javascript angularjs json

Answer 1

Answer №1

Initially, $http already returns a promise that you can work with:

return $http.get(...)

On another note, remember that you can chain promises together. If you need to preprocess data before returning it, you can do so like this:

return $http.get(..).then(function(response){
    var data = response.data;
    [..process..]
    **return data;**
}, function(rejection){
    // handle rejections
});

In a typical scenario, you bind data to your directive using ng-model and call services in the controller. To manage asynchronous data loading, you can use scope.$watch or attrs.$observe on the model to update your directive.

This approach allows for flexibility in how data is loaded, making directives reusable regardless of the data source or changes in the application.

Don't forget the importance of the bolded text mentioned earlier, as it ensures that your processed data is available for subsequent 'then' calls.

Lastly, when using the link function provided by the directive API, consider including:

link  : function(scope, element, attrs){
    attrs.$observe('myVariable', function(){
         // update internal state of directive here
    });
}

'myVariable' refers to an attribute named my-variable in the directive's invocation.

If "myData" is loaded in the view controller as shown below:

jsonrc.get().then(function(response){
    $scope.myData = response.data;
});

To take it a step further, consider creating a service for your holiday service to load data only once at application startup:

App.service('MyService',['$http', function($http){
    var promise = $http.get([URL]);
    return function(){  // define your service
        var self = this;
        promise.then(function(response){
            self.data = response.data;
        });
    }
}]);

Now, in your main controller, you can utilize: scope.data = MyService.data; Alternatively, you can integrate it into your directive or use getters as needed. This level of abstraction can be advantageous, though not always necessary.

If anything was left out, please let me know.

Answer 2

Initially, $http already returns a promise that you can work with:

return $http.get(...)

On another note, remember that you can chain promises together. If you need to preprocess data before returning it, you can do so like this:

return $http.get(..).then(function(response){
    var data = response.data;
    [..process..]
    **return data;**
}, function(rejection){
    // handle rejections
});

In a typical scenario, you bind data to your directive using ng-model and call services in the controller. To manage asynchronous data loading, you can use scope.$watch or attrs.$observe on the model to update your directive.

This approach allows for flexibility in how data is loaded, making directives reusable regardless of the data source or changes in the application.

Don't forget the importance of the bolded text mentioned earlier, as it ensures that your processed data is available for subsequent 'then' calls.

Lastly, when using the link function provided by the directive API, consider including:

link  : function(scope, element, attrs){
    attrs.$observe('myVariable', function(){
         // update internal state of directive here
    });
}

'myVariable' refers to an attribute named my-variable in the directive's invocation.

If "myData" is loaded in the view controller as shown below:

jsonrc.get().then(function(response){
    $scope.myData = response.data;
});

To take it a step further, consider creating a service for your holiday service to load data only once at application startup:

App.service('MyService',['$http', function($http){
    var promise = $http.get([URL]);
    return function(){  // define your service
        var self = this;
        promise.then(function(response){
            self.data = response.data;
        });
    }
}]);

Now, in your main controller, you can utilize: scope.data = MyService.data; Alternatively, you can integrate it into your directive or use getters as needed. This level of abstraction can be advantageous, though not always necessary.

If anything was left out, please let me know.

Answer 3

Answer №2

This method might be beneficial.

To start, include the async call in a parent controller (the directive's parent controller).
Next, isolate your directive's scope and add a model to it.

scope: {
  data: '=',
}

In your controller, declare a variable like this: $scope.directiveData = {}
Set the value of that variable with the result of the async call.

Don't forget to pass it to your directive using:

<mydirective data="directiveData"></mydirective>

Access this variable in your template using the name data, or scope.data in the link function.

You may need mocked data for directiveData, or add an ng-if to prevent crashing (when trying to display data for the first time and directiveData is an empty object).

Answer 4

This method might be beneficial.

To start, include the async call in a parent controller (the directive's parent controller).
Next, isolate your directive's scope and add a model to it.

scope: {
  data: '=',
}

In your controller, declare a variable like this: $scope.directiveData = {}
Set the value of that variable with the result of the async call.

Don't forget to pass it to your directive using:

<mydirective data="directiveData"></mydirective>

Access this variable in your template using the name data, or scope.data in the link function.

You may need mocked data for directiveData, or add an ng-if to prevent crashing (when trying to display data for the first time and directiveData is an empty object).

Answer 5

Answer №3

Optimize your factory by caching the httpPromise and creating it only once.

App.factory( 'jsonsrc', function( $http ){
     var httpPromise;
     function load () {
         httpPromise = $http.get( 'termine_2016.json' )
             .then(function onFullfilled(response) {
                  //return data for chaining
                  return response.data;
             }).catch( function onRejected(response) {
                  console.log( "[jsonsrc] request didnot work!" );
                  //throw to reject promise
                  throw response.status;
             });
          return httpPromise;
      };
      function get () {
          if (httpPromise) return httpPromise;
          //Otherwise
          return load();
      };
      return { load: load,
               get:  get
             };
});

The usage of $q.defer has been replaced with .then and .catch methods as the .success and .error methods are now deprecated according to the AngularJS $http Service API Reference -- deprecation notice.

Your directive can be simplified as follows:

App.directive('app2directive',function(){
    return {
        restrict:"ACE",
        scope:{},
        replace:true,
        templateUrl:"templates/cal_directive3.html",
        controller: function ($scope, $attrs, jsonsrc, $log, YEARS, MONTHS, DAYS) { 
            jsonsrc.get().then (function (data) {
                $scope.tonnen = data ;
            }).catch( function(error){
                console.log( "error", error ) ;
            });
        })
    }
});

By implementing this approach, the XHR GET request in the jsonsrc factory is executed only once while each instance of app2directive can retrieve the data independently for its own isolate scope.

Answer 6

Optimize your factory by caching the httpPromise and creating it only once.

App.factory( 'jsonsrc', function( $http ){
     var httpPromise;
     function load () {
         httpPromise = $http.get( 'termine_2016.json' )
             .then(function onFullfilled(response) {
                  //return data for chaining
                  return response.data;
             }).catch( function onRejected(response) {
                  console.log( "[jsonsrc] request didnot work!" );
                  //throw to reject promise
                  throw response.status;
             });
          return httpPromise;
      };
      function get () {
          if (httpPromise) return httpPromise;
          //Otherwise
          return load();
      };
      return { load: load,
               get:  get
             };
});

The usage of $q.defer has been replaced with .then and .catch methods as the .success and .error methods are now deprecated according to the AngularJS $http Service API Reference -- deprecation notice.

Your directive can be simplified as follows:

App.directive('app2directive',function(){
    return {
        restrict:"ACE",
        scope:{},
        replace:true,
        templateUrl:"templates/cal_directive3.html",
        controller: function ($scope, $attrs, jsonsrc, $log, YEARS, MONTHS, DAYS) { 
            jsonsrc.get().then (function (data) {
                $scope.tonnen = data ;
            }).catch( function(error){
                console.log( "error", error ) ;
            });
        })
    }
});

By implementing this approach, the XHR GET request in the jsonsrc factory is executed only once while each instance of app2directive can retrieve the data independently for its own isolate scope.

Ways to guarantee that the factory promise is fulfilled prior to the execution of the

Answer №1

Answer №2

Answer №3

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