Accessing JSON data from an external file using AngularJS's $http method

I am new to Angular and not very comfortable with JavaScript. I am attempting to create an app using the Ionic framework. I have successfully retrieved a list from a JSON file stored in a variable, but now I am trying to use $http.get() to fetch it from a remote file in my project directory.

.service('staffServices', ['$q', '$http', staffService]);

function staffService($q, $http) {
  var staffs = {};
  var promise = $http.get("/js/jsons/settings.json")
  .success(function(response) {
    staffs = response.staffSettings;
    console.log(staffs);    //RECEIVES THE DATA
  });
  console.log(staffs);      //EMPTY OBJECT


  return {
    loadAllSettings: function () {          
      return $q.when(staffs);          
    },
    query: function (params) {
      return filterFilter(staffs, params);
    },
    get: function (params) {
      return this.query(params)[0];
    }
  }
};

I am having trouble accessing the result outside of the .success() function. I'm not sure if this is because of my lack of knowledge in JavaScript or my beginner level in Angular. Any assistance would be appreciated.

This is my controller below. self.settings always remains empty and does not populate

.controller("staffCtrl", function (staffServices) {
  var self = this;

  self.settings = [];
  staffServices.loadAllSettings()
  .then(function (settings) {
    self.settings = [].concat(settings);
    console.log(settings);
  });
});

Answer №1

One potential issue lies in how the $q and promise are being handled. Consider the following alternative approach:

// Omitted unnecessary return functions for now
.service('staffServices', ['$q', '$http', staffService]);

function staffService($q, $http) {
    var deferredPromise = $q.defer();
    var staffs = {};
    var promise = $http.get("/js/jsons/settings.json")
    .success(function(response) {
        staffs = response.staffSettings;
        console.log(staffs);
        deferredPromise.resolve(staffs);
    })
    .error(function(){
        deferredPromise.reject();
        console.log('Unsucessful json call');
    });

    return {
        loadAllSettings: function () {
            return deferredPromise.promise;
        }
    }
};

.controller("staffCtrl", function (staffServices) {
    var self = this;
    self.settings = [];
    staffServices.loadAllSettings()
    .then(function (settings) {
        console.log(settings);
        self.settings = [].concat(settings);
    });
});

Answer №2

When you make the $http.get call, it runs asynchronously. This means that any code inside the .success callback will only execute once the request has been resolved.

If you try to access the data outside of the .success callback, the request may not have completed yet, so you'll still be working with an empty variable or outdated information.

If you're having trouble understanding asynchronous operations, I recommend checking out this question which explains it well.

Regarding the issue with JSON not returning properly, it seems like the loadAllSettings() function should return a promise using $q.when instead of just the staffSettings object. Make sure to handle the response correctly in your controller by setting staffs equal to response and accessing the staffSettings attribute.

.controller("staffCtrl", function (staffService) {
  var self = this;

  self.settings = [];
  staffService.loadAllSettings()
  .then(function (settings) {
    self.settings = [].concat(settings.staffSettings);
    console.log(settings);
  });
});

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