Exploring scope in an angular service

Question

Exploring scope in an angular service

My goal is to show a success message after clicking a button. Since I need this functionality in multiple controllers, I decided to implement it using a service. However, I am facing issues accessing the scope.

index.html

<div ng-controller="uploadController">     
    <div class="col-md-6" ng-click="uploadFile()" >
        <div class="form-group has-success" id="divsubmitbtn">
            <button type="submit" id="submit" class="btn btn-custom"
            ng-click="submitData()" ng-disabled="isDisableSubmit">
           <span class="glyphicon glyphicon-upload"></span> Upload</button>
       </div>
   </div>
   <div class=" col-md-12">
       <div ng-show="showError" ng-class="{fade:doFade}" class="alert alert-success">
    <strong>Success:</strong> {{successMessage}}
     </div>
  </div>
</div>

controller.js

app.controller('uploadController', ['$scope','$timeout','$rootScope','displayMsgService',function($scope,$timeout,$rootScope,displayMsgService) {

$scope.uploadFile = function($scope,displayMsgService){     
        $scope.displayMsgService.show();
        };

$rootScope.submitData = function() {
            $scope.uploadFile();
       };
}]);

service.js

app.factory('displayMsgService',function() {
  return {
      show : function($scope){
                $scope.showError = false;
                $scope.doFade = false;           
                $scope.showError = true;
                $scope.successMessage = "success";

                $timeout(function(){
                    $scope.doFade = true;
                }, 2500);
            }
        } 
});

I encountered the following error: Cannot read property 'displayMsgService' of undefined

Can someone point out what I might be missing?

javascript angularjs

Answer 1

Answer №1

TYPOGRAPHICAL ERRORS

$rootScope.submitData = function() {
            $scope.uploadFile();
       };

It appears you intended to write: $scope.submitData, as submitData is a method within the $scope of your controller;

Also, $scope.displayMsgService.show(); should be corrected to displayMsgService.show();, given that displayMsgService pertains to the injected service and not directly related to the $scope (not a method within the controller scope).

To rectify this in your controller, consider:

$scope.uploadFile = function($scope, displayMsgService){     
    displayMsgService.show($scope);
    };

The factory function structure you had necessitates passing the controller's scope; if you make alterations to the scope within the factory, it is advisable to call $scope.$apply() afterwards.

CORRECTION AND ELUCIDATION

The syntax show : function($scope) does not imply direct injection of the scope into your factory method. Rather, it signifies that the show function requires an argument; you could substitute show : function($scope) with show : function(arg) for similar outcomes.

Hence, you need to pass the scope from your controller like so: displayMsgService.show($scope)

However, passing your controller $scope to the factory/service is not recommended: refer to these discussions: Passing current scope to an AngularJS Service and injecting scope into a service

To circumvent the necessity of passing the scope to the service, here are two alternatives:

1. Broadcasting

In your scenario, a straightforward approach would be to broadcast an event from your service to inform the controller about the completion of file upload:

 $rootScope.$broadcast('uploadDone');

NOTE: Once again, ensure that $rootScope is injected into the service/factory.

In your controller:

$scope.$on('uploadDone',function(){
 //modify $scope here
}

2. PROMISES

For asynchronous events such as uploads, considering the use of promises might be beneficial. Despite being more intricate than broadcasting, they are commonly employed in such scenarios.

In your controller:

uploadMsgService.upload()
  .then(function{
  //adjust $scope accordingly
  });

And in your service:

app.factory('uploadMsgService',function($q) {
  var deferred = $q.defer();
  doTheUpload(inputData,function(err,data){
  if(err){deferred.reject("there was an error:"+err);}
  deferred.resolve(data);   
  })
  return deferred.promise;
});

For further insights on using promises with AngularJS:

Official documentation on implementing $q with AngularJS

thinkster tutorial

Answer 2

TYPOGRAPHICAL ERRORS

$rootScope.submitData = function() {
            $scope.uploadFile();
       };

It appears you intended to write: $scope.submitData, as submitData is a method within the $scope of your controller;

Also, $scope.displayMsgService.show(); should be corrected to displayMsgService.show();, given that displayMsgService pertains to the injected service and not directly related to the $scope (not a method within the controller scope).

To rectify this in your controller, consider:

$scope.uploadFile = function($scope, displayMsgService){     
    displayMsgService.show($scope);
    };

The factory function structure you had necessitates passing the controller's scope; if you make alterations to the scope within the factory, it is advisable to call $scope.$apply() afterwards.

CORRECTION AND ELUCIDATION

The syntax show : function($scope) does not imply direct injection of the scope into your factory method. Rather, it signifies that the show function requires an argument; you could substitute show : function($scope) with show : function(arg) for similar outcomes.

Hence, you need to pass the scope from your controller like so: displayMsgService.show($scope)

However, passing your controller $scope to the factory/service is not recommended: refer to these discussions: Passing current scope to an AngularJS Service and injecting scope into a service

To circumvent the necessity of passing the scope to the service, here are two alternatives:

1. Broadcasting

In your scenario, a straightforward approach would be to broadcast an event from your service to inform the controller about the completion of file upload:

 $rootScope.$broadcast('uploadDone');

NOTE: Once again, ensure that $rootScope is injected into the service/factory.

In your controller:

$scope.$on('uploadDone',function(){
 //modify $scope here
}

2. PROMISES

For asynchronous events such as uploads, considering the use of promises might be beneficial. Despite being more intricate than broadcasting, they are commonly employed in such scenarios.

In your controller:

uploadMsgService.upload()
  .then(function{
  //adjust $scope accordingly
  });

And in your service:

app.factory('uploadMsgService',function($q) {
  var deferred = $q.defer();
  doTheUpload(inputData,function(err,data){
  if(err){deferred.reject("there was an error:"+err);}
  deferred.resolve(data);   
  })
  return deferred.promise;
});

For further insights on using promises with AngularJS:

Official documentation on implementing $q with AngularJS

thinkster tutorial

Answer 3

Answer №2

If you're looking for an alternative approach, consider using a base controller instead of a Service.

Base Controller

app.controller('CustomDisplayController', ['$scope', function ($scope) {
  $scope.displayMessage = function () {
    // Set all the necessary variables and messages here
  };
}]);

Simply include the base controller in any other controller where you need that specific functionality.

Custom Upload Controller

app.controller('UploadFileController', ['$scope', '$controller', function ($scope, $controller) {
  // Inject the scope into the custom display controller
  $controller('CustomDisplayController', { $scope: $scope });

  // Process your data and then call the displayMessage function from CustomDisplayController
  $scope.uploadFile = function(){     
    // Data processing logic here
    ...
    // Display the message
    $scope.displayMessage();
  };
}]);

Answer 4

If you're looking for an alternative approach, consider using a base controller instead of a Service.

Base Controller

app.controller('CustomDisplayController', ['$scope', function ($scope) {
  $scope.displayMessage = function () {
    // Set all the necessary variables and messages here
  };
}]);

Simply include the base controller in any other controller where you need that specific functionality.

Custom Upload Controller

app.controller('UploadFileController', ['$scope', '$controller', function ($scope, $controller) {
  // Inject the scope into the custom display controller
  $controller('CustomDisplayController', { $scope: $scope });

  // Process your data and then call the displayMessage function from CustomDisplayController
  $scope.uploadFile = function(){     
    // Data processing logic here
    ...
    // Display the message
    $scope.displayMessage();
  };
}]);

Exploring scope in an angular service

Answer №1

1. Broadcasting

2. PROMISES

Answer №2

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