Swift iOS 9 UITableView reloadData after CoreData finished - ios

Question

I try to update my tableview after my REST-call is finished and all entities are stored in CoreData. I tried dispatch_asynch but the tableview doesn't reload when expected. I am using a UIRefreshControl to trigger refreshing. Usually, the correct tableview data is displayed after 2 refreshes. I have no idea why.
I can confirm that my tableview instance IS NOT nil.
#IBAction func refreshTriggered(sender: UIRefreshControl) {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), {
self.evMan.retrieveAndSaveEvents(self.pubMan.getAllPublishers())
dispatch_async(dispatch_get_main_queue()) {
self.tableView.reloadData()
self.refreshControl?.endRefreshing()
}
}
}
This is my retrieveAndSaveEvents method from my 'EventManager' evMan:
func retrieveAndSaveEvents(forPublishers: [PUBLISHERS]) {
for publisher in forPublishers {
let pubId = publisher.id as Int
let str = "/publishers/\(pubId)/events"
// resty is an instance of my REST-api wrapper
self.resty.GET(self.server, route: str, onCompletion: {json in
let result = json.asArray
for var i = 0; i < result!.count; i++ {
if !self.isIDAlreadyInDB(json[i]["id"].asInt!) {
let newEv = NSEntityDescription.insertNewObjectForEntityForName("EVENTS", inManagedObjectContext: self.context!) as! EVENTS
newEv.headline = json[i]["headline"].asString!
newEv.id = json[i]["id"].asInt!
newEv.content = json[i]["content"].asString!
newEv.ofPublisher = publisher
do {
try self.context!.save()
} catch _ {
}
print("New Event from \(publisher.name): \(newEv.headline)")
}
}
})
}
}
FYI, here's my cellForRowAtIndexPath: (I am using a Custom UITableViewCell)
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = self.tableView.dequeueReusableCellWithIdentifier("eventCell") as? EventCell
let curEv = evMan.getEvents()[indexPath.row]
cell?.infoLabel.text = curEv.ofPublisher?.name
cell?.myImageView.image = UIImage(named: "icon.png")
cell?.detailLabel.text = curEv.headline
cell?.timeLabel.attributedText = NSAttributedString(string: self.dateFormatter.stringFromDate(curEv.updatedAt))
cell?.contentView.backgroundColor = UIColor.clearColor()
cell?.backgroundColor = UIColor(white: 1.0, alpha: 0.5)
return cell!
}
Here is my REST-wrapper:
class REST: NSObject {
// Basic Auth
let sConfig = ServerConfig()
var username = "rest"
var password = "resttest"
override init() {
username = sConfig.getUserLogin().user
password = sConfig.getUserLogin().pass
}
func GET(server: String, route: String, onCompletion: (JSON) -> Void) {
let route = server+route
makeHTTPGetRequest(route, onCompletion: { json, err in
onCompletion(json as JSON)
})
}
func makeHTTPGetRequest(path: String, onCompletion: ServiceResponse) {
let request = NSMutableURLRequest(URL: NSURL(string: path)!)
let loginString = NSString(format: "%#:%#", username, password)
let loginData: NSData = loginString.dataUsingEncoding(NSUTF8StringEncoding)!
let base64LoginString = loginData.base64EncodedStringWithOptions(NSDataBase64EncodingOptions())
let loginvalue = "Basic " + base64LoginString
// add Headers
request.addValue(loginvalue, forHTTPHeaderField: "Authorization")
request.addValue("application/json", forHTTPHeaderField: "Accept")
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithRequest(request, completionHandler: {data, response, error -> Void in
let json:JSON = JSON(data: data!)
onCompletion(json, error)
})
task.resume()
}
}

Answer 1

#IBAction func refreshTriggered(sender: UIRefreshControl) {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), {
self.evMan.retrieveAndSaveEvents(self.pubMan.getAllPublishers())
})
dispatch_async(dispatch_get_main_queue()) {
self.tableView.reloadData()
self.refreshControl?.endRefreshing()
}
}
Now, you cannot guarantee reloadData() happens after self.evMan.retrieveAndSaveEvents(self.pubMan.getAllPublishers()) , because they are not happen in the same queue. And probably, reloadData() happens before retrieve.
Option 1:
You should put the block :
dispatch_async(dispatch_get_main_queue()) {
self.tableView.reloadData()
self.refreshControl?.endRefreshing()
}
at the end of func retrieveAndSaveEvents(self.pubMan.getAllPublishers())
Option 2 :
#IBAction func refreshTriggered(sender: UIRefreshControl) {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), {
self.evMan.retrieveAndSaveEvents(self.pubMan.getAllPublishers())
dispatch_async(dispatch_get_main_queue()) {
self.tableView.reloadData()
self.refreshControl?.endRefreshing()
}
})
}
EDIT:
I did not see there is another queue in retrieveAndSaveEvents
So, put the
dispatch_async(dispatch_get_main_queue()) {
self.tableView.reloadData()
self.refreshControl?.endRefreshing()
}
at the end of:
self.resty.GET(self.server, route: str, onCompletion: {json in
let result = json.asArray
for var i = 0; i < result!.count; i++ {
if !self.isIDAlreadyInDB(json[i]["id"].asInt!) {
let newEv = NSEntityDescription.insertNewObjectForEntityForName("EVENTS", inManagedObjectContext: self.context!) as! EVENTS
newEv.headline = json[i]["headline"].asString!
newEv.id = json[i]["id"].asInt!
newEv.content = json[i]["content"].asString!
newEv.ofPublisher = publisher
do {
try self.context!.save()
} catch _ {
}
print("New Event from \(publisher.name): \(newEv.headline)")
}
}
})