Unable to connect #IBSegueAction - segue

I have single view controller with a UIButton containing the following code:
import UIKit
class ViewController: UIViewController {
required init?(coder: NSCoder) {
super.init(coder: coder)
func makeAnotherController(coder: NSCoder, sender: Any?, segueIdentifier: String?) -> ViewController? {
return ViewController(coder: coder)
According to Apple's docs, this is the correct signature for a #IBSegueAction, and it compiles OK, but I'm unable to connect the button to the #IBSegueAction by dragging from the storyboard scene to the assistant editor.
I can connect without issue to other outlets or actions.
Any thoughts? Xcode 11 bug or am I doing something wrong?
Briefly, Apple's docs say…
Create a connection from a segue to an #IBSegueAction method on its source view controller. On new OS versions that support Segue Actions, that method will be called … An IBSegueAction method takes up to three parameters: a coder, the sender, and the segue’s identifier. The first parameter is required, and the other parameters can be omitted from your method’s signature if desired
I'm unable to complete the first step (create a connection)

This was my misunderstanding of Apple's docs. When they say…
Create a connection from a segue to an #IBSegueAction method on its source view controller.
they literally mean drag from the line that represents the segue to the view controller.


Prism Library Dialog Service

The following sample never worked for me:
Where the dialogService comming from?
public MainWindowViewModel(IDialogService dialogService)
_dialogService = dialogService;
How can I add the dialog service?
protected override Window CreateShell()
var w = Container.Resolve<MainWindow>();
return w;
It's have to go within the RegisterTypes?
Where the dialogService comming from?
From the container. When resolving, the container also resolves all dependencies.
How can I add the dialog service?
You don't have to and normally should shouldn't either. Most of the time, the default implementation provided by the prism framework suffices.
It's have to go within the RegisterTypes?
If you use Unity, every non-concrete type has to be registered to be able to be resolved. That means, prism's dialog service implementation is registered somewhere. Have a look at the code of your application's base class as a starting point.

kotlin.KotlinNullPointerException while accessing Data from local Room Database?

I am new into Kotlin and trying to learn, how to fetch Data with retrofit and store this data into a Room DB. But as soon as i start the Activity where this process takes place i get a NullPointerException.
EDIT: As far as i could find out now, my "database" in the RoomViewmodel class is still NULL when i want to access it, even though i have an override oncreate function, where it is created
Here is also a link to the GitHub repository from the mini-project I'm working on: https://github.com/Engin92/Dog_Breeds/tree/RoomDatabase
here is my complete errorlist:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.dogbreeds, PID: 14803
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.dogbreeds/com.example.Breedlist.activity.DetailedViewActivity}: kotlin.KotlinNullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3782)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3961)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:91)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:149)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:103)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2386)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:213)
at android.app.ActivityThread.main(ActivityThread.java:8178)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1101)
Caused by: kotlin.KotlinNullPointerException
at com.example.Breedlist.activity.DetailedViewActivityRepository.getBreeds(DetailedViewActivityRepository.kt:23)
at com.example.Breedlist.activity.DetailedViewActivityViewModel.getAllBreedList(DetailedViewActivityViewModel.kt:23)
at com.example.Breedlist.activity.DetailedViewActivity.onCreate(DetailedViewActivity.kt:42)
at android.app.Activity.performCreate(Activity.java:8086)
at android.app.Activity.performCreate(Activity.java:8074)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1313)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3755)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3961) 
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:91) 
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:149) 
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:103) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2386) 
at android.os.Handler.dispatchMessage(Handler.java:107) 
at android.os.Looper.loop(Looper.java:213) 
at android.app.ActivityThread.main(ActivityThread.java:8178) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1101) 
The important part of DetailedViewActivity
class DetailedViewActivity : AppCompatActivity() {
lateinit var breedRecyclerView: RecyclerView
lateinit var detailedViewActivityViewModel: DetailedViewActivityViewModel
override fun onCreate(savedInstanceState: Bundle?) {
breedRecyclerView = findViewById(R.id.breedRecyclerView)
detailedViewActivityViewModel = ViewModelProviders.of(this).get(
Toast.makeText(this,"No internet connection. Showing cached list!",Toast.LENGTH_LONG).show()
detailedViewActivityViewModel.getAllBreedList().observe(this, Observer<List<CurrentBreedResponseItem>> { breedList ->
} ....
the class RoomViewModel, where i build the DB (where i Think the error is, the var database is still NULL, after trying to access (write/read) it)
class RoomViewModel : Application() {
companion object {
var database: BreedDatabase? = null
override fun onCreate() {
database = Room.databaseBuilder(applicationContext, BreedDatabase::class.java, "breed_db").fallbackToDestructiveMigration().build()
getBreeds function in DetailedViewActivityRepository:
fun getBreeds() : LiveData<List<CurrentBreedResponseItem>>
return RoomViewModel.database!!.currentBreedDao().getAllBreeds()
getAllBreedList function in DetailedViewActivityViewModel
fun getAllBreedList(): LiveData<List<CurrentBreedResponseItem>>
return detailedViewActivityRepository.getBreeds()
There are two problem in your code. The first one is very clear you are trying to access a null object and you are getting NullPointerException. So be careful when you use !! operator.
The reason you are getting it is, inside your RoomViewModel your database instance is null.
class RoomViewModel : Application() {
companion object {
var database: BreedDatabase? = null
override fun onCreate() {
database = Room.databaseBuilder(applicationContext, BreedDatabase::class.java, "breed_db")
You may think you are initializing the database instance in onCreate() but the onCreate() is not getting called. The reason is to make the application class work you need to add it to your AndroidManifest.xml file.
Add this RoomViewModel class to your AndroidManifest.xml file like this.
We do it as application tag's name attribute as you can see above.
This will fix your null pointer exception. But your program will again crash, because you are using Kotlin and do make room work with kotlin this thing needs to be added in your app level build.gradle file.
kapt "android.arch.persistence.room:compiler:1.1.1"
After adding it to your app level build.gradle inside dependencies block. Sync your project and run it should work.
If you want to learn more about Room Database in Android, you can check this Room Database Tutorial.
Hope this will help you.

MPMusicPlayerController slow to respond when systemMusicPlayer, fast when application

I have a music app that uses the MPMusicPlayerController.
I originally wrote it using the systemMusicPlayer option under iOS 9.
I had some trouble with the player not shutting down correctly under certain circumstances so I switched to the appplicationMusicPlayer
(see Quitting app causes error "Message from debugger: Terminated due to signal 9")
However, as an application player, I can't get a lot of the benefits like control center handling, bluetooth data display, etc.
So, I switched back to the systemMusicPlayer.
I have also changed to Xcode 9.2 and a compile target of iOS 10.3.
Now when I run my app, it can take several seconds for it to respond to controls like play/pause or next/previous. My whole UI is painfully unresponsive.
I tried switching back to applicationMusicPlayer, recompiled, and sure enough - the UI is at normal speed.
So now I'm in a crappy position - with systemMusicPlayer, the app is barely usable, but with applicationMusicPlayer I lose a ton of capabilities.
This seems directly related to either iOS 11.2.2 on my iPhone, or something to do with targeting iOS 10.3+
Does anyone have any information about what is going on and how to fix it
I created a very basic player and it seems to work fine in either mode, so now I'm puzzled - I'll be testing other MP commands to see what the
issue is but since even my UI slows down I'm not sure.
I believe I've found the culprit to be NotificationCenter, and also getting States from the MPMusicPlayerController. I've updated my sample code below which shows the problem. Once running, clicking the 'next' button will be slow sometimes, but clicking 'previous' can cause delays of up to two seconds!!
Here is the basic code if you want to create a simple player.
Be sure to add three buttons in the storyboard and connect them accordingly.
// ViewController.swift
// junkplayer
import UIKit
import MediaPlayer
let notificationCenter = NotificationCenter.default
let myMP:MPMusicPlayerController = MPMusicPlayerController.systemMusicPlayer
//let myMP:MPMusicPlayerController = MPMusicPlayerController.applicationMusicPlayer()
class ViewController: UIViewController {
#IBOutlet weak var xxx: UIButton!
#IBOutlet weak var nextbut: UIButton!
#IBOutlet weak var prevbut: UIButton!
var qrySongs = MPMediaQuery()
override func viewDidLoad() {
// Do any additional setup after loading the view, typically from a nib.
myMP.repeatMode = MPMusicRepeatMode.none
myMP.shuffleMode = MPMusicShuffleMode.off
override func didReceiveMemoryWarning() {
// Dispose of any resources that can be recreated.
override func viewWillAppear(_ animated: Bool) {
#IBAction func nextbut(_ sender: Any) {
#IBAction func prevbut(_ sender: Any) {
#IBAction func playbut(_ sender: UIButton) {
qrySongs = MPMediaQuery.songs()
myMP.setQueue(with: qrySongs)
func startMPNotifications(){
notificationCenter.addObserver(self, selector: #selector(showNowPlaying), name: .MPMusicPlayerControllerNowPlayingItemDidChange, object: myMP)
notificationCenter.addObserver(self, selector: #selector(handlePlayState), name: .MPMusicPlayerControllerPlaybackStateDidChange, object: myMP)
func stopMPNotifications(){
notificationCenter.removeObserver(self, name: .MPMusicPlayerControllerPlaybackStateDidChange, object: myMP)
notificationCenter.removeObserver(self, name: .MPMusicPlayerControllerNowPlayingItemDidChange, object: myMP)
#objc func handlePlayState(){
if myMP.playbackState == .playing {
print("handlePlayState playback state = playing")
print("handlePlayState playback state NOT playing")
print("handlePlayState going to shownowplaying")
#objc func showNowPlaying(){
if myMP.nowPlayingItem != nil {
print("shownowplaying nowplaying not null")
The app seems to lock up once you start playing, but if you swipe up to show the Control Centre then dismiss it, the app starts working fine immediately.
I am having the same problem. I think it’s something wrong with the API. It's especially slow for large queries. But you can put a predicate on the quart, that allows no cloud music to go on it.
For anyone browsing this thread in the future, this was a known bug within all versions of iOS 11.2. It affected anyone using the systemMusicPlayer.
Apple sure does love to discourage us third party music app developers, eh? ;)
Regardless of my conspiracy theories (and I'm sure you have yours too), this bug was fixed in iOS 11.3.
We warn users on iOS 11.2 about the bug and recommend that they upgrade to iOS 11.3 for a (more or less) lag-free experience.
I ran into this problem today - working code just stopped running correctly, but I found a (partial) workaround:
\\Do anything that updates (like changing the song title in the UI) in the selector called by this notification
NotificationCenter.default.addObserver(self, selector: #selector(remoteMusicChange), name: NSNotification.Name.MPMusicPlayerControllerNowPlayingItemDidChange, object: nil)
The issue is that calls to say go to the next track for systemMusicPlayer are no longer (always) happening immediately. If you wait for the notification, at least you can be sure systemMusicPlayer has updated.
The problem with this is sometimes it can take a perceptibly long time for that notification to fire (and sometimes it's instant).
EDIT: https://forums.developer.apple.com/thread/96287 I am guessing this is related to these issues
EDIT2: Tested another related issue quickly in iOS12 and the problem no longer existed (changing playback speed) and the pauses when changing songs went away.

3d touch navigate to specific viewController

I am trying to implement 3d Touch and I want to navigate to a specific viewController in a Master - Detail app.
The viewController I am aiming to get to is the third controller in the hierarchy:
MasterViewController ----> SettingsViewController ----> ThirdViewController
I can access the ThirdViewController in normal operation through TabBarItem (connected via segue to SettingsViewController right from the IB) and then via a UIButton (connected via segue to ThirdViewController right from the IB) to the ThirdViewController.
i.e in MasterViewController ---> (tap barButtonItem) ----> SettingsViewControler ----> (tap uiButton) ---> ThirdViewController.
I have already amended the info.plist and 3D touch works fine and can call my action:
func application(application: UIApplication, performActionForShortcutItem shortcutItem: UIApplicationShortcutItem, completionHandler: (Bool) -> Void) {
var shortcutDictionary = shortcutItem.userInfo;
let shortcutString1 = shortcutDictionary!["key1"] as! String
if (shortcutString1 == "value1") {
// how do i get from here to the settingsController??
already have tried:
let viewController = MasterViewController() viewController.settingsButton.sendActionsForControlEvents(.TouchUpInside)
which gives me an error:fatal error trying to unwrap an optional value!
although this exists in MasterViewController
#IBOutlet weak var settingsButton: UIButton!
This is the code I use for the shortcut....
func actionFromShortcut(sender: AnyObject!) {
let dispatchTime: dispatch_time_t = dispatch_time(DISPATCH_TIME_NOW, Int64(0.1 * Double(NSEC_PER_SEC)))
dispatch_after(dispatchTime, dispatch_get_main_queue(), {
self.performSegueWithIdentifier("shotcutToSettings", sender: nil)
//some other stuff here.....
Also as per #MattLong's comment I have duplicated the segues to my controllers (one with and one without animation). That way the shortcut transition seems simultaneous when the action is called from the shortcut.
You will notice a delay of 0.1. It is to give the MasterViewController time to load cause whenever I tried to call the shortcut from cold (app not running) I would end up with the viewController I requested but there would be an empty MasterViewController to return to and hence crash....

How to use connectionDidFinishDownloading:destinationURL: and connectionDidFinishLoading:

I have implemented both the NSURLConnectionDownloadDelegate, NSURLConnectionDataDelegate delegate methods as given below.
The problem is that after connection:didReceiveResponse: , connectionDidFinishDownloading:destinationURL: is called but not connectionDidFinishLoading: Even connection:didReceiveData: is not called.
When I comment the NSURLConnectionDownloadDelegate methods, the other three are called without any issues.
I have a NSURLConnections which gets JSON from server. The NSURLConnectionDataDownloading delegate methods are used by newsstand to download issues.
How do i manage this?
Here are all the delegate methods than I am implementing
- (void)connection:(NSURLConnection *)connection didWriteData:(long long)bytesWritten totalBytesWritten:(long long)totalBytesWritten expectedTotalBytes:(long long)expectedTotalBytes {
- (void)connectionDidFinishDownloading:(NSURLConnection *)connection destinationURL:(NSURL *)destinationURL {
- (void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
- (void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
- (void) connectionDidFinishLoading:(NSURLConnection *)connection {
Here is my .h file
#interface FirstTopViewController : UIViewController <NSURLConnectionDownloadDelegate, NSURLConnectionDataDelegate, NSURLConnectionDelegate, UITableViewDataSource, UITableViewDelegate>
This is how I am connecting to server to get JSON
[[NSURLConnection alloc] initWithRequest:req delegate:self startImmediately:YES];
This is the code for downloading an issue if needed
NSURLRequest *urlReq = [NSURLRequest requestWithURL:myURL];
NKAssetDownload *asset = [currentIssue addAssetWithRequest:urlReq];
[asset downloadWithDelegate:self];
The problem is with the call to get JSON from server. Issue downloading works fine.
NSURLConnectionDataDelegate define delegate methods used for loading data to memory.
NSURLConnectionDownloadDelegate: delegate methods used to perform resource downloads directly to a disk file.
Then if you implemented connectionDidFinishDownloading:destinationURL: in your delegate. That will inform NSURLConnection you want to download the data to a disk file other than to memory as NSData. The
NSURLConnectionDataDelegate method won't get called. If you eliminate connectionDidFinishDownloading:destinationURL: from your delegate class implementation, connection:DidReceiveData: will get called instead.
For your case, implement two helper delegates for different usage.
When you want to get your JSON data in -connection:didReceiveData:, you need to set the delegate to an object which implements NSURLConnectionDataDelegate; when you want to download an issue to a file, the delegate needs to be an object that implements NSURLConnectionDownloadDelegate. A single class can't do both at once.
This is not explained very well in the NSURLConnection docs, but the comments in NSURLConnection.h make it a little more explicit:
An NSURLConnection may be used for loading of resource data
directly to memory, in which case an
NSURLConnectionDataDelegate should be supplied, or for
downloading of resource data directly to a file, in which case
an NSURLConnectionDownloadDelegate is used. The delegate is
retained by the NSURLConnection until a terminal condition is
encountered. These two delegates are logically subclasses of
the base protocol, NSURLConnectionDelegate.