javascript - JSON to Initialize Data in Service

I'm developing a small AngularJS app and I'm currently struggling with creating a service.

I have a service that serves as a backend for providing contacts (name, address...).
Until now they were hard-coded as an array in the service (instance.contacts=[...]), but now I'm trying to read them from a json file :

myModule.factory('contactService', ['$http',function ($http) {
    var instance = {};
    $http.get('contacts.json').success(function (data) {
        instance.contacts = data;
    });
    return instance;
}]);

I see in my browser console that the file has been read successfully, but I don't see any change on-screen.

So I tried the following instead, and it worked :

myModule.factory('contactService', ['$http',function ($http) {
    var instance = {
        contacts:[]
    };
    $http.get('contacts.json').success(function (data) {
        angular.forEach(data, function(item) {
            instance.contacts.push(item);
        });
    });
    return instance;
}]);

I don't know why the second code snippet works, and not the first. Could someone please help me understand ?