swift do task after the preview task is finished - mysql

Question

In my swift 2 app i would like to make an http-post-request to get data of my mysql database. After that I would like to write this data into my core data.
I have the code part for request and write.
How do I get the following structure.
Request Data
if request data complete write in into core data
Could this be the correct thing?
This is my SyncMYSQL function in my Sync.swift file.
class func SyncMYSQL() {
print("START SYNC MYSQL")
UIApplication.sharedApplication().networkActivityIndicatorVisible = true
let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
let defaults = NSUserDefaults.standardUserDefaults()
let request = NSMutableURLRequest(URL: NSURL(string: "https://xxx")!)
request.HTTPMethod = "POST"
let postString = "userid=12"
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
data, response, error in
// if no internet connection
guard error == nil && data != nil else {
print("error=\(error)")
return
}
let responseString = NSString(data: data!, encoding: NSUTF8StringEncoding)!
let fetchRequest = NSFetchRequest(entityName: "ITEMS")
fetchRequest.returnsObjectsAsFaults = false
do {
let results = try managedObjectContext!.executeFetchRequest(fetchRequest)
for managedObject in results {
let managedObjectData:NSManagedObject = managedObject as! NSManagedObject
managedObjectContext!.deleteObject(managedObjectData)
}
} catch let error as NSError {
print("Detele all data in ITEMS error : \(error) \(error.userInfo)")
}
var x = 0
while (x < responseString.count ) {
let newItem = NSEntityDescription.insertNewObjectForEntityForName("ITEMS", inManagedObjectContext: managedObjectContext!) as! CoreData_ITEMS
newItem.name = responseString[x]
x++
}
dispatch_sync(dispatch_get_main_queue(),{
print("FINISH MYSQL")
UIApplication.sharedApplication().networkActivityIndicatorVisible = false
});
}
task.resume()
}
This function i call from my view controller like this way:
func RequestData() {
Sync.SyncMYSQL()
print ("Start Core Data")
let fetchRequest = NSFetchRequest(entityName: "ITEMS")
do {
try data = managedObjectContext!.executeFetchRequest(fetchRequest) as! [CoreData_ITEMS]
} catch { }
Table.reloadData()
}

Answer 1

You should use closure blocks as callback when the operation ends
class func SyncMYSQL(onSuccess: ()->()){
// your custom events
// your custom events
// your custom events
if MYSQLisSynced == true {
// when MYSQL is synced you can call the success block
onSuccess()
}
}
In other file when you call the function SyncMYSQL() you have to specify the on success block
SyncMYSQL { () -> () in
//custom callback actions
}