Catch event in view from another class - ios

Question

I have async task with request where i fetching products every 3 seconds in class Item.
class Item: NSManagedObject {
var is_fetching:Bool = false;
func fetchProducts(q: String) {
let task = session.dataTaskWithRequest(urlRequest, completionHandler: {
(data, response, error) in
self.is_fetching = true;
//some code
if ((response as! NSHTTPURLResponse).statusCode == 202) {
sleep(3)
self.fetchProducts(q)
return
}
if ((response as! NSHTTPURLResponse).statusCode == 200) {
self.is_fetching = false;
}
})
task.resume()
}
}
And i have UITableViewController where i show data from response. How do i update my cells when status code is 200:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath:
indexPath) as! CartTableViewCell
if item.is_fetching {
cell.fetchIndicator.startAnimating();
} else {
cell.fetchIndicator.stopAnimating();
cell.fetchIndicator.hidden = true;
}
}

Answer 1

You can do it in few ways.
NSNotificationCenter (simplest).
You can post notifications, that will trigger your controller's methods. Looks like this:
// if response.code == 200
NSNotificationCenter.defaultCenter().postNotificationName("kSomeConstatnString", object: nil)
...
// in viewDidLoad of your controller:
NSNotificationCenter.defaultCenter().addObserver(self, selector: "updateTable", object: nil)
// you also need implement updateTable() func inside your controller
// or if you need just update table
NSNotificationCenter.defaultCenter().addObserver(self.tableView, selector: "reloadData", object: nil)
// do not forget to delete observer (for instance in -deinit method)
NSNotificationCenter.defaultCenter().removeObserver(self)
// or tableView. also you can specify for which selector, if you use couple of them.
Delegate pattern.
You can describe your protocol, make your controller implement this protocol and save it as instance in your model object. Then just call methods from delegate. Details here.
Block callbacks.
Create block for action and call it from your model. For example:
// inside controller
model.refreshCallback = { Void in
self.tableView.reloadData() // or whatever
}
// inside model
var refreshCallback: (() -> Void)?
...
// if result.code == 200
if let callback = refreshCallback {
callback()
}

Answer 2

Use one of the UITableView’s reload functions, perhaps:
func reloadRowsAtIndexPaths(_ indexPaths: [NSIndexPath],
withRowAnimation animation: UITableViewRowAnimation)
This will cause it to ask again for the cell in question. Make sure you do this on the main thread.