What is the best way to prevent using a function expression in order to return a local variable within an AngularJS factory?

Question

What is the best way to prevent using a function expression in order to return a local variable within an AngularJS factory?

Is there a way to return "stories" by setting "vm.stories = storyDataAsFactory.stories" instead of the current method "vm.stories = storyDataAsFactory.stories()" ? I've tried various combinations without any luck. Additionally, it seems that I can call storyDataAsFactory.getStories without using parentheses, which aligns with how it's set up. However, when I create a function to return self.stories, it doesn't seem to work.

The following code is functioning correctly -

storyDataAsFactory.$inject = ['$http', '$q'];

angular.module('ccsApp').factory('storyDataAsFactory', storyDataAsFactory);

function storyDataAsFactory($http, $q) {
    var self = this;
    var stories = [];

    function getStories(url) {
        url = url || '';

        var deferred = $q.defer();

        $http({method: 'GET', url: url})
            .success(function (data, status, headers, config) {
                self.stories = data;

                deferred.resolve(data);
            })
            .error(function (data, status, headers, config) {
                deferred.reject(status);
            });

        return deferred.promise;
    }

    function listStories() {
        return self.stories;
    }

    return {
        stories: listStories,

        getStories: getStories('stories.json')
    };
}

UPDATE:

I'm still facing issues. Here's my updated code based on community suggestions -

storyDataAsFactory.$inject = ['$http', '$q'];

angular.module('ccsApp').factory('storyDataAsFactory', storyDataAsFactory);

function storyDataAsFactory($http, $q) {
    var stories = [];

    function getStories(url) {
        url = url || '';

        if (url !== '') {
            var deferred = $q.defer();

            //check if ajax call has already been made;
            //if so, data exists in cache as local variable
            if (stories.length !== 0) {
                deferred.resolve();
                return deferred.promise;
            }

            $http({method:'GET', url:url})
                .success(function (data, status, headers, config) {
                    stories = data;

                    deferred.resolve();
                })
                .error(function (data, status, headers, config) {
                    deferred.reject(status);
                });

            return deferred.promise;
        } else {
            alert('URL was empty.');
        }
    }

    return {
        stories: stories,

        getStories: function(url) {
            getStories(url);
        }
    };
}

storyDataAsFactory.stories does not provide any output. Please note that I have confirmed that resolve was executed properly, ruling out asynchronous issues. This problem has been consuming my time for hours without any breakthrough.

javascript angularjs

Answer 1

Answer №1

It seems there may be some confusion between Angular service and factory concepts:

Let's explore the differences below:

Angular service:

module.service( 'serviceName', function );
Result: When you declare serviceName as an injectable argument, you will receive
        an instance of the function passed to module.service.

Angular factory

module.factory( 'factoryName', function );
Result: Declaring factoryName as an injectable argument will provide you with
        the value returned by invoking the function reference passed to
        module.factory. If you want to access the methods of the factory, they should be included 
        along with the returned value.

The Angular service version of your code would look like this:

schoolCtrl.service('storyDataAsService', storyDataAsService);

function storyDataAsService($http, $q) {
    var self = this;
    var stories = [];

    this.getStories = function(url) {
        url = url || '';

        var deferred = $q.defer();

        $http({method: 'GET', url: url})
            .success(function (data, status, headers, config) {
                self.stories = data;

                deferred.resolve(data);
            })
            .error(function (data, status, headers, config) {
                deferred.reject(status);
            });

        return deferred.promise;
    };
    this.stories = function(){
        // @TODO add return value
    }
}

The Angular factory version would be:

storyDataAsFactory.$inject = ['$http', '$q'];

angular.module('ccsApp').factory('storyDataAsFactory', storyDataAsFactory);

function storyDataAsFactory($http, $q) {
    var self = this;
    var stories = [];

    function getStories(url) {
        url = url || '';

        var deferred = $q.defer();

        $http({method: 'GET', url: url})
            .success(function (data, status, headers, config) {
                self.stories = data;

                deferred.resolve(data);
            })
            .error(function (data, status, headers, config) {
                deferred.reject(status);
            });

        return deferred.promise;
    }

    return {
        stories: function() {
            // @TODO add return value
        },

        getStories: getStories
    };
}

Answer 2

It seems there may be some confusion between Angular service and factory concepts:

Let's explore the differences below:

Angular service:

module.service( 'serviceName', function );
Result: When you declare serviceName as an injectable argument, you will receive
        an instance of the function passed to module.service.

Angular factory

module.factory( 'factoryName', function );
Result: Declaring factoryName as an injectable argument will provide you with
        the value returned by invoking the function reference passed to
        module.factory. If you want to access the methods of the factory, they should be included 
        along with the returned value.

The Angular service version of your code would look like this:

schoolCtrl.service('storyDataAsService', storyDataAsService);

function storyDataAsService($http, $q) {
    var self = this;
    var stories = [];

    this.getStories = function(url) {
        url = url || '';

        var deferred = $q.defer();

        $http({method: 'GET', url: url})
            .success(function (data, status, headers, config) {
                self.stories = data;

                deferred.resolve(data);
            })
            .error(function (data, status, headers, config) {
                deferred.reject(status);
            });

        return deferred.promise;
    };
    this.stories = function(){
        // @TODO add return value
    }
}

The Angular factory version would be:

storyDataAsFactory.$inject = ['$http', '$q'];

angular.module('ccsApp').factory('storyDataAsFactory', storyDataAsFactory);

function storyDataAsFactory($http, $q) {
    var self = this;
    var stories = [];

    function getStories(url) {
        url = url || '';

        var deferred = $q.defer();

        $http({method: 'GET', url: url})
            .success(function (data, status, headers, config) {
                self.stories = data;

                deferred.resolve(data);
            })
            .error(function (data, status, headers, config) {
                deferred.reject(status);
            });

        return deferred.promise;
    }

    return {
        stories: function() {
            // @TODO add return value
        },

        getStories: getStories
    };
}

Answer 3

Answer №2

When working with your factory storyDataAsFactory, it is important to note that self serves as the provider. However, in order to utilize the local variable stories, you must refrain from accessing the field self.stories. I have addressed this issue and resolved the bugs in your code.

Update: If you intend on using stories as a field instead of a getter, you cannot modify the local variable (which references the original array). The only way to make changes is by directly modifying the original array.

storyDataAsFactory.$inject = ['$http', '$q'];

angular.module('ccsApp', [] /*XXX added []*/ []).factory('storyDataAsFactory', storyDataAsFactory);

function storyDataAsFactory($http, $q) {
    var stories = [];

    function getStories(url) {
        url = url || '';

        if (url !== '') {
            var deferred = $q.defer();

            // Check if data already exists in cache
            if (stories.length !== 0) {
                deferred.resolve();
                return deferred.promise;
            }

            $http({method:'GET', url:url})
                .success(function (data, status, headers, config) {
                    // Ensure original array remains intact
                    stories.splice(0, stories.length);
                    data.forEach(function(x) { stories.push(x); });

                    deferred.resolve();
                })
                .error(function (data, status, headers, config) {
                    deferred.reject(status);
                });

            return deferred.promise;
        } else {
            alert('URL was empty.');
        }
    }

    return {
        stories: stories, // Ensure original array does not get lost

        getStories: function(url) {
            getStories(url);
        }
    };
}

// ------------ tests --------------------
describe('storyDataAsFactory.stories()', function() {
  var $httpBackend, $http, $q, storyDataAsFactory;
  
  beforeEach(module('ccsApp'));
  
  beforeEach(inject(function(_$httpBackend_) {
    $httpBackend = _$httpBackend_;
    $httpBackend.whenGET('stories.json').respond([1, 2, 3]);
  }));
  
  beforeEach(inject(function(_$http_, _$q_, _storyDataAsFactory_) {
    $http = _$http_;
    $q = _$q_;
    storyDataAsFactory = _storyDataAsFactory_;
  }));
  
  it('should return empty array before ajax resolved', function() {
    storyDataAsFactory.getStories('stories.json');
    expect(storyDataAsFactory.stories).toEqual([]);
    $httpBackend.flush();
  });
  
  it('should return filled array after ajax resolved', function() {
    storyDataAsFactory.getStories('stories.json');
    $httpBackend.flush();
    expect(storyDataAsFactory.stories).toEqual([1, 2, 3]);
  });
});

// ------------ run tests --------------------
window.onload = function() {
  var jasmineEnv = jasmine.getEnv();
  var htmlReporter = new jasmine.HtmlReporter();
  jasmineEnv.addReporter(htmlReporter);
  jasmineEnv.execute();
};

<script src="https://cdnjs.cloudflare.com/ajax/libs/jasmine/1.3.1/jasmine.js"></script>
<link href="https://cdnjs.cloudflare.com/ajax/libs/jasmine/1.3.1/jasmine.css" rel="stylesheet"/>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jasmine/1.3.1/jasmine-html.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.2.28/angular-mocks.js"></script>

Answer 4

When working with your factory storyDataAsFactory, it is important to note that self serves as the provider. However, in order to utilize the local variable stories, you must refrain from accessing the field self.stories. I have addressed this issue and resolved the bugs in your code.

Update: If you intend on using stories as a field instead of a getter, you cannot modify the local variable (which references the original array). The only way to make changes is by directly modifying the original array.

storyDataAsFactory.$inject = ['$http', '$q'];

angular.module('ccsApp', [] /*XXX added []*/ []).factory('storyDataAsFactory', storyDataAsFactory);

function storyDataAsFactory($http, $q) {
    var stories = [];

    function getStories(url) {
        url = url || '';

        if (url !== '') {
            var deferred = $q.defer();

            // Check if data already exists in cache
            if (stories.length !== 0) {
                deferred.resolve();
                return deferred.promise;
            }

            $http({method:'GET', url:url})
                .success(function (data, status, headers, config) {
                    // Ensure original array remains intact
                    stories.splice(0, stories.length);
                    data.forEach(function(x) { stories.push(x); });

                    deferred.resolve();
                })
                .error(function (data, status, headers, config) {
                    deferred.reject(status);
                });

            return deferred.promise;
        } else {
            alert('URL was empty.');
        }
    }

    return {
        stories: stories, // Ensure original array does not get lost

        getStories: function(url) {
            getStories(url);
        }
    };
}

// ------------ tests --------------------
describe('storyDataAsFactory.stories()', function() {
  var $httpBackend, $http, $q, storyDataAsFactory;
  
  beforeEach(module('ccsApp'));
  
  beforeEach(inject(function(_$httpBackend_) {
    $httpBackend = _$httpBackend_;
    $httpBackend.whenGET('stories.json').respond([1, 2, 3]);
  }));
  
  beforeEach(inject(function(_$http_, _$q_, _storyDataAsFactory_) {
    $http = _$http_;
    $q = _$q_;
    storyDataAsFactory = _storyDataAsFactory_;
  }));
  
  it('should return empty array before ajax resolved', function() {
    storyDataAsFactory.getStories('stories.json');
    expect(storyDataAsFactory.stories).toEqual([]);
    $httpBackend.flush();
  });
  
  it('should return filled array after ajax resolved', function() {
    storyDataAsFactory.getStories('stories.json');
    $httpBackend.flush();
    expect(storyDataAsFactory.stories).toEqual([1, 2, 3]);
  });
});

// ------------ run tests --------------------
window.onload = function() {
  var jasmineEnv = jasmine.getEnv();
  var htmlReporter = new jasmine.HtmlReporter();
  jasmineEnv.addReporter(htmlReporter);
  jasmineEnv.execute();
};

<script src="https://cdnjs.cloudflare.com/ajax/libs/jasmine/1.3.1/jasmine.js"></script>
<link href="https://cdnjs.cloudflare.com/ajax/libs/jasmine/1.3.1/jasmine.css" rel="stylesheet"/>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jasmine/1.3.1/jasmine-html.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.2.28/angular-mocks.js"></script>

What is the best way to prevent using a function expression in order to return a local variable within an AngularJS factory?

Answer №1

Angular service:

Angular factory

The Angular service version of your code would look like this:

The Angular factory version would be:

Answer №2

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