Swift Flow of Control (Function Calls) - swift

Question

I am writing this code:
func checkUserImages() {
if (self.imagesAdded.count == 0) {
self.success()
} else {
if (self.checkNetwork() == false) {
self.displayNoNetworkConnection()
} else if (self.checkUser() == false) {
print("THERE IS NO CURRENT USER")
} else {
self.progressHUD = MBProgressHUD.showAdded(to: self.view, animated: true)
self.progressHUD.label.text = "Loading"
if (self.imagesAdded.contains("Header")) {
print("CALL 1")
self.uploadImage(image: self.headerImageView.image!, imageType: "headerPicture")
}
if (self.imagesAdded.contains("Profile")) {
print("CALL 2")
self.uploadImage(image: self.profileImageView.image!, imageType: "profilePicture")
}
self.addImageLinksToDatabase()
}
}
}
func uploadImage(image: UIImage, imageType: String) {
let imageUploadData = image.mediumQualityJPEGData
storageReference.child("users").child("\(imageType)s").child("\(currentUser!.uid)\(imageType)").putData(imageUploadData, metadata: nil) { (metadata, error) in
if let error = error {
self.progressHUD.hide(animated: true)
self.displayError(title: "Error", message: error.localizedDescription)
} else {
self.imageData[imageType] = metadata?.downloadURL()?.absoluteString
}
}
}
func addImageLinksToDatabase() {
databaseReference.child("users").child(currentUser!.uid).child("userDetails").updateChildValues(self.imageData, withCompletionBlock: { (error, ref) in
if let error = error { // Checks for an error
self.progressHUD.hide(animated: true)
self.displayError(title: "Error", message: error.localizedDescription)
} else {
self.success()
}
})
}
func success() {
self.progressHUD.hide(animated: true)
self.performSegue(withIdentifier: "successfulAddPhotosSegue", sender: self)
}
It appears that the last line of code in the checkUserImages() function gets called before the the images finish uploading in the uploadImage() function. Because of this, there is no data ready for the addImageLinksToDatabase() function yet. Is this a multi-threading error and how do I go about fixing the flow so that the images upload before addImageLinksToDatabase() is called?

Answer 1

This is due to multi-threading. The solution is simple. Just move the last line of code from checkUserImages() to the end of uploadImage().
Eg.
func uploadImage(image: UIImage, imageType: String) {
let imageUploadData = image.mediumQualityJPEGData
storageReference.child("users").child("\(imageType)s").child("\(currentUser!.uid)\(imageType)").putData(imageUploadData, metadata: nil) { (metadata, error) in
if let error = error {
self.progressHUD.hide(animated: true)
self.displayError(title: "Error", message: error.localizedDescription)
} else {
self.imageData[imageType] = metadata?.downloadURL()?.absoluteString
}
}
self.addImageLinksToDatabase()
}
That should work perfectly.