Working with Model async data and TableView - ios

Question

I'm creating an app and I have all the logic done, but I want to do a Code refactoring and create MVC pattern. But I dealing with some asynchronous informations, that came from API.
/MenuViewController
Alamofire.request(.GET, Urls.menu).responseJSON { request in
if let json = request.result.value {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)) {
let data = JSON(json)
var product: [Product] = []
for (_, subJson): (String, JSON) in data {
product += [Product(id: subJson["id"].int!, name: subJson["name"].string!, description: subJson["description"].string!, price: subJson["price"].doubleValue)]
}
dispatch_async(dispatch_get_main_queue()) {
self.products += product
self.tableView.reloadData()
}
}
}
}
This is my code, already working. But I want to create a Model that will handle this and just return the array of Products to my MenuViewController.
Model/Menu
class Menu {
var products: [Product] = []
init() {
Alamofire.request(.GET, Urls.menu).responseJSON { request in
if let json = request.result.value {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)) {
let data = JSON(json)
var product: [Product] = []
for (_, subJson): (String, JSON) in data {
product += [Product(id: subJson["id"].int!, name: subJson["name"].string!, description: subJson["description"].string!, price: subJson["price"].doubleValue)]
}
dispatch_async(dispatch_get_main_queue()) {
self.products += product
}
}
}
}
}
func totalOfProducts() -> Int {
return self.products.count
}
func getProducts() -> [Product]? {
return self.products
}
func getProductFromIndex(index: Int) -> Product {
return self.products[index]
}
}
But I got my self thinking, how I gonna get the main_queue to another class?
So I tried something like this:
class MenuViewControlvar: UITableViewController {
var products: [Product] = []
let menu: Menu = Menu()
// MARK: View Controller Lifecycle
override func viewDidLoad() {
super.viewDidLoad()
if let products = menu.getProducts() {
self.tableView.reloadData()
}
// rest of the code
But didn't worked. My TableView is never updated.
I was wondering if I can do this, or I've to keep my Alamofire code in my viewDidLoad() from my MenuViewController
Thank you.

Answer 1

I am just giving you a direction with the step I would follow (Not writing the code thinking you can work it out):
First, write a networking class that accepts network request along with a competition block. Completion block shall be executed as soon as networking is done. This is a wrapper class and can be used across classes.
Second, write a model class that has all the parameters necessary for view controller's functionalities/view drawing.
Third, from view controller, call the networking class. In completion block, pass the model setting, table reload code and any code to remove loading overlay/indicator. This block should get executed on main queue.
Fourth, add code to show loading overlay/indicator before you trigger networking.

Answer 2

Delegation is an ideal solution for this problem of updating your model data and your view based on an asynchronous network call and it’s pretty much the same technique that is implemented throughout the iOS SDK to solve the same problem. There are many benefits of delegation over observation, another viable solution.
First, move your networking code to a separate class
class NetworkingController {
Create a protocol that view controllers can conform to. This provides the loose coupling between your network operations and your views to effectively maintain separation between the MVC layers.
#protocol NetworkingControllerDelegate: class {
func menuDataDidUpdate()
}
Have the networking controller support a property for its delegate
weak var delegate: NetworkingControllerDelegate?
In summary your networking class now looks something like this:
#protocol NetworkingControllerDelegate: class {
func menuDataDidUpdate()
}
class NetworkingController {
weak var delegate: NetworkingControllerDelegate?
// Insert networking functions here.
}
Then, have your view controller conform to this protocol like so
class MenuViewController: NetworkingControllerDelegate {
and create a new network controller in your view controller
var myNetworkController = NetworkController()
and set the delegate of your network controller instance to be your view controller
myNetworkController.delegate = self
Then in your networking code, when the network request has completed and your model has been updated, make a call to the networking controller's delegate.
delegate.menuDidUpdate()
Create the implementation for this method in your view controller since it is now the delegate for your networking code.
func menuDidUpdate() {
// Update your menu.
}
This makes your view controller look something like:
class MenuViewController: NetworkingControllerDelegate {
var myNetworkController = NetworkController()
override func viewDidLoad() {
myNetworkController.delegate = self
}
// MARK: NetworkingControllerDelegate
func menuDidUpdate() {
// Update your menu.
}
}
This is just the outline of the implementation to give you the necessary information about how to proceed. Fully adapting this to your problem is up to you.