writing a simple Angular Service - angularjs

Question

OK, I've built services before but obviously I don't actually know what makes them tick, since I can't seem to debug this ultra-simple service call:
app.js:
var gridApp = angular.module('gridApp', []);
gridApp.controller('mainController', ['$scope', '$http', 'dataService',
function($scope, dataService) {
$scope.message = 'I am Angular and I am working.';
var init = function(){
console.log(dataService.foo);
console.log(dataService.getData());
};
init();
}]);
dataService.js:
(function() {
'use strict';
angular
.module('gridApp')
.service('dataService', dataService)
dataService.$inject = [];
function dataService() {
console.log("I am the dataService and I am loaded");
var foo = 1;
function getData () {
return 2;
}
}
})();
I see this on-screen: I am Angular and I am working. so Angular is loading.
I see this in console: I am the dataService and I am loaded so the dataService is actually being loaded.
But then the console.log is:
undefined (line 8)
TypeError: dataService.getData is not a function (line 9)
What am I missing?

Answer 1

The previous answers are correct in that your $http injection was wrong, but you are also not attaching your service functions to the service:
function dataService() {
var dataService = this; //get a reference to the service
//attach your functions and variables to the service reference
dataService.foo = 1;
dataService.getData = function() {
return 2;
};
}
An Angular service is very simply an object class. It is also a singleton, meaning it's instantiated only once per run of your app. When the service is instantiated it is very much akin to calling the new operator on your dataService "class":
var $dataService = new dataService();
So, when you inject dataService into your controller, you are actually getting an instance, $dataService, of your dataService "class".
See this blog entry for further reading: https://tylermcginnis.com/angularjs-factory-vs-service-vs-provider-5f426cfe6b8c#.sneoo52nk

Answer 2

You are missing the 2nd parameter $http in the function. The named parameters and the actual parameters in function need to be the same, same order and same number. What happened before is that dataService was being assigned an $http instance and the actual dataService was not injected at all because there was no 3rd parameter to inject it into.
var gridApp = angular.module('gridApp', []);
gridApp.controller('mainController', ['$scope', '$http', 'dataService',
function($scope, $http, dataService) {
// ----was missing-----^
$scope.message = 'I am Angular and I am working.';
var init = function(){
console.log(dataService.foo);
console.log(dataService.getData());
};
init();
}]);

Answer 3

We have missed the second param '$http' in function. Just add the '$http' param, it should work fine
var gridApp = angular.module('gridApp', []);
gridApp.controller('mainController', ['$scope', '$http', 'dataService',
function($scope,$http, dataService) {
$scope.message = 'I am Angular and I am working.';
var init = function(){
console.log(dataService.foo);
console.log(dataService.getData());
};
init();
}]);

Answer 4

This is how I've been taught to set up services:
function dataService() {
var dataService = {};
var _foo = 1;
var _getData = function () { return 2; }
dataService.foo = _foo;
dataService.getData = _getData;
return dataService;
}
I believe this facilitates public/private methods/vars.

Answer 5

For reference, this is the full code accessing my service:
app.js:
var gridApp = angular.module('gridApp', []);
// create the controller and inject Angular's $scope
gridApp.controller('mainController', ['$scope', 'dataService', function($scope, dataService) {
// create a message to display in our view
$scope.message = 'Angular is working';
var init = function(){
getPackageData();
};
var getPackageData = function (){
return dataService.getData().then(
function successCallback(response) {
console.log(response);
},
function errorCallback(response) {
console.log(response);
}
);
};
init();
}]);
dataService.js:
(function() {
'use strict';
angular
.module('gridApp')
.service('dataService', dataService)
dataService.$inject = ['$http'];
function dataService($http) {
var dataService = {};
var _getData = function () {
return $http({
method: 'GET',
url: 'data/packages.json'
})
.then(function successCallback(response) {
return response;
},
function errorCallback(response) {
return response;
});
}
dataService.getData = _getData;
return dataService;
}
})();