completionhandler

I'm having trouble understanding completion handlers. I have a textFieldEditingDidChange IBAction that calls first a verify() function on the textfield input and then an if statement on the boolean returned by apply. The problem is that the if statement starts before verify() has finished . Here is the code: @IBOutlet weak var myTextField: UITextField! @IBAction func myTextFieldEditingDidChange(sender: AnyObject) { let yo = verify(myTextField.text!) print("\(yo)") // it always prints "true" because verify hasn't finished } func verify(myText: String) -> Bool { var result = true // some code

I have checked many docs but could not found solution for Resuming tasks using NSURLSession when app removed from background or on device reboot. I am dealing with amazon S3 to upload some files, In that I am able to Upload file to S3 using NSURLSessionUploadTask, when app is in foreground as well as in background. Resume task when app crashed due to any other reason while uploading and if app is not removed from background. Restart task if I reboot device while uploading and if app is not removed from background. Here is my code to achive resume fuctionality written in

I'm trying to write a completion handler for a function that checks if a user is a member of a team in firebase. I have a public class customFunctions in which I created a function ifUserIsMember . I seem to be a little stuck on the idea of completion handlers, and can't seem to figure out how to check the bool value on completion (if that makes sense). Here's my code for the class: import Foundation import GeoFire import FirebaseDatabase public class customFunctions { func ifUserIsMember(userid: String, completionHandler: @escaping (Bool) -> ()) { let ref = FIRDatabase.database().reference()

I am accessing instance method inside closure in swift, self reference become nil in some cases which result crash my program. I tried to access using [weak self] but it failed to call the instance method when self is nil . [weak self] () -> () in The whole point of [weak self] is to not create a reference to self (probably to avoid circular links and memory leaks) so that it can be released. If that happens, then self will be nil . You should either not use [weak self] or, better yet probably, be prepared to handle the case of self having been released and set to nil . guard let strong = self

In the following code none of the completion handlers ever get executed. The one explanation I was able to find is this Bug in iPhone Simulator 5.1 with Xcode 4.5 using UIManagedDocument . It says that it might be a bug in iPhone simulator 5.1 . However, I've tried iPhone simulators 6.0, 6.1 and 7.0, none of them worked. I'll really appreciate your help. (By the way, I've seen this code in the Stanford iOS course, lecture 14) NSURL *url = [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject]; url = [url URLByAppendingPathComponent:@

I am confused surrounding the syntax for a completion handler in swift 3. In the function below, after parsing an xml file from a web service call, it should return a variable (an array [String:String] ). My attempt is below, but obviously it is incorrect. enum HistoryKey { case success([String:String]) case failure(String) } private func getHistoryKeys(searchterm: String, completion: @escaping () -> HistoryKey) { let url = PubmedAPI.createEsearchURL(searchString: searchterm) let request = URLRequest.init(url: url as URL) let task = session.dataTask(with: request) { (data, response, error) in