Access HTTP GET JSON property in angular controller

Question

I am using a factory in angular.js and $http.get method to grab and process JSON data. The JSON data seems successfully parsed into factory, but I have problem access property of this JSON data.

Here is my js code:

var app = angular.module("app", []);      

app.factory('mainInfo', function($http) { 

    var obj = {content:null};
    //the php will return json data below
    $http.get('http://localhost/test.php').success(function(response){ 
        obj.content = response.records;

    });    

    return obj;    
});


app.controller('Ctrl', function($scope, mainInfo){
    $scope.foo = mainInfo.content;
}) ;

Now if I try to access foo within Ctrl controller, the webpage will display no data:
<div ng-controller="Ctrl">Controller: {{foo}}</div>
However, if I change to $scope.foo = mainInfo in the Ctrl, then the webpage will display correctly the JSON data.

May I know what is the proper way to access mainInfo.content property in Ctrl controller?

The reason why I need to access JSON property is because I need to pre-process the data. I intend to use these data in a Chart, as in below controller. Currently this controller is not working either, because I have the same problem accessing JSON property as in the Ctrl controller.

app.controller("LineCtrl", function ($scope, mainInfo) {
    var timePoints = [];
    var percentagePoints = [];
    var i = 0;
    for( i = 0; i < mainInfo.content.length; i ++) {
        timePoints.push(mainInfo.content[i].Time);
        percentagePoints.push(mainInfo.content[i].Percentage);
    }

    $scope.labels = timePoints;

    $scope.data = percentagePoints;

    $scope.onClick = function (points, evt) {
        console.log(points, evt);
    };
});

The json data:

{
"records": [
    {
        "Id": "1",
        "Time": "2015-07-25 08:00:00",
        "Percentage": "60"
    },
    {
        "Id": "2",
        "Time": "2015-07-25 09:00:00",
        "Percentage": "70"
    },
    {
        "Id": "3",
        "Time": "2015-07-25 10:00:00",
        "Percentage": "80"
    }
    ]
}

With regards to the factory-controller communication, I am just referring the solution from another post: reference

Answer 1

$http.get returns a promise -- your problem is that you are returning "obj" immediately, and your controller tries to access the data before the $http.get promise is resolved.

use $http like so (no need to use $q.defer() as shown in the other comment):

var app = angular.module("app", []);      

app.factory('mainInfo', function($http) { 
    var getRecordsPromise = $http.get('http://localhost/test.php').then(function(response){ 
        //whatever is returned here will be accessible in the .then that is chained
        return response.data.records;
    });    

    return {
        getRecords: getRecordsPromise
    };    
});


app.controller('Ctrl', function($scope, mainInfo){
    mainInfo.getRecords.then(function (records) {
        $scope.foo = records;
    });
}) ;

Answer 2

Try this instead

var obj = {content: []};
obj.$promise = $http.get('http://localhost/test.php').then(function(response) {
    angular.copy(response.data.records, obj.content);
    return response.data;
});
return obj;

The reason your former method didn't work was because you were re-assigning the content property of obj, thus destroying any previous references.

This is also why using $scope.foo = mainInfo worked because the reference to obj (via mainInfo) was maintained.

Using angular.copy maintains the previous reference whilst populating the data.

---

That should take care of references in the template that get updated when the $http promise resolves (due to $http triggering a digest cycle). For accessing the data in your controller, use the $promise property

$scope.foo = mainInfo.content;
mainInfo.$promise.then(function(data) {
    // access data.records here
});

---

Maintaining the data inside your factory is a good idea if you share your factory with multiple consumers (eg controllers). They may all reference mainInfo.content and mainInfo.$promise and all will be accessing the same data set.