I want to write a project has a notification can print data which stored in main viewcontroller, but when notification fired, always get empty data.
In the ViewController
arrPerson = [String]()
override func viewDidLoad() {
super.viewDidLoad()
arrPerson.append("Peter")
arrPerson.append("Jack")
setNotification()
}
func printTheName() {
print("In printTheName")
print("arrPerson:\(arrPerson.count)")
for x in arrPerson {
print(x)
}
}
func setNotification() {
let notification = UNMutableNotificationContent()
notification.title = "title"
notification.subtitle = ""
notification.body = "body"
notification.sound = UNNotificationSound.default()
let trigger = UNTimeIntervalNotificationTrigger(timeInterval: 60, repeats: true)
let request = UNNotificationRequest(identifier: "check", content: notification, trigger: trigger)
let notificationCenter = UNUserNotificationCenter.current()
notificationCenter.add(request) { (error) in
if error != nil {
print("notificationCenter.add ERROR:\(error)")
// Handle any errors.
}
}
}
In the Appdelegate
func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: #escaping (UNNotificationPresentationOptions) -> Void) {
print("In userNotificationCenter")
ViewController().printTheName()
}
The code will print out "userNotificationCenter","In printTheName","arrPerson:0".
I need get data from notification. Why arrPerson.count is 0 when call printTheName from notification?
Try to programatically instantiate the viewController using a window in your appdelegate.
You will be able to fetch the count then in your notification center.Or since your viewController class is the landing screen, Call the userNotifationCenter method in your main Class and not here.
I'm new to Swift, and trying my hands with UIWebView app that loads default url, with option to perform quick action and load a different url.
Problem is when I request the quick action url, code executes but the new url is not loading. So I'm missing something in the flow somewhere.
Here is the code:
import UIKit
import WebKit
class ViewController: UIViewController, UIWebViewDelegate {
#IBOutlet var webView: UIWebView!
override func loadView() {
super.loadView()
self.webView = UIWebView()
self.view = self.webView!
}
override func viewDidLoad() {
print("view did load")
super.viewDidLoad()
let url = NSURL(string: "google.com")
let req = NSURLRequest(URL:url!)
webView.loadRequest(req)
webView.delegate = self
}
func loadUrl2() {
loadView()
let url = NSURL(string: "example.com")
print(url)
let req = NSURLRequest(URL:url!)
self.webView!.loadRequest(req)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
I was experimenting and added loadView to loadUrl2, as I was getting
fatal error: unexpectedly found nil while unwrapping an Optional value
before that.
Edited to Include loading secondary link:
Here are the changes and files you'll need to make to the App Delegate
enum ShortcutIdentifier: String {
case OpenNewLink
case OpenBetterLink
init?(fullIdentifier: String) {
guard let shortIdentifier = fullIdentifier.componentsSeparatedByString(".").last else {
return nil
}
self.init(rawValue: shortIdentifier)
}
}
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
if let shortcutItem = launchOptions?[UIApplicationLaunchOptionsAnnotationKey] as? UIApplicationShortcutItem {
handleShortcut(shortcutItem)
return false
}
return true
}
func application(application: UIApplication, performActionForShortcutItem shortcutItem: UIApplicationShortcutItem, completionHandler: (Bool) -> Void) {
completionHandler(handleShortcut(shortcutItem))
}
private func handleShortcut(shortcutItem: UIApplicationShortcutItem) -> Bool {
let shortcutType = shortcutItem.type
guard let ShortcutIdentifier = ShortcutIdentifier(fullIdentifier: shortcutType) else {
return false
}
return selectLinkForIdentifier(ShortcutIdentifier)
}
private func selectLinkForIdentifier(identifier: ShortcutIdentifier) -> Bool {
guard let mainView = self.window?.rootViewController as? ViewController else {
return false
}
switch identifier {
case .OpenNewLink:
mainView.urlString = "http://www.bing.com"
mainView.loadWebView(mainView.urlString)
return true
case.OpenBetterLink:
mainView.urlString = "http://www.duckduckgo.com"
mainView.loadWebView(mainView.urlString)
return true
}
}
I also made changes in the MainVC
class ViewController: UIViewController, UIWebViewDelegate {
#IBOutlet var webView: UIWebView!
var urlString: String? = nil
override func viewDidLoad() {
super.viewDidLoad()
setUpWebView()
webView.delegate = self
view.addSubview(webView)
}
func setUpWebView() {
webView = UIWebView()
webView.frame = CGRectMake(0, 0, view.frame.width, view.frame.height)
loadWebView(urlString)
}
func loadWebView(var urlString: String?) {
if urlString == nil {
urlString = "http://www.google.com"
}
let url = NSURL(string: urlString!)
let req = NSURLRequest(URL:url!)
webView.loadRequest(req)
}
}
Be sure to add NSAppTransportSecurity dictionary to your .plist and add NSAllowsArbitraryLoads key set to YES.
I tested it and it should work for you.
I'm working through an example below and received an error message:
Cannot convert value of type 'NSObject -> () -> CentralViewController
to expected argument type 'TransferServiceDelegate?'
I'm trying to complete a delegation, it is erring out when I'm trying to initialize 'scanner'. Any help would be appreciated..thanks!:
import UIKit
import Foundation
protocol TransferServiceScannerDelegate: NSObjectProtocol {
func didStartScan()
func didStopScan()
func didTransferData(data: NSData?)
}
class TransferServiceScanner: NSObject{
weak var delegate: TransferServiceScannerDelegate?
init(delegate: TransferServiceScannerDelegate?) {
self.delegate = delegate
super.init()
}
}
class CentralViewController: UIViewController,
TransferServiceScannerDelegate {
*let scanner: TransferServiceScanner = TransferServiceScanner(self)*
func didStartScan(){}
func didStopScan(){}
func didTransferData(data: NSData?){}
}
First way:
lazy var scanner: TransferServiceScanner = {
let scanner = TransferServiceScanner(delegate: self)
return scanner
}()
I don't think use delegate in init is a good way and necessary, you also can do like this:
class TransferServiceScanner: NSObject{
weak var delegate: TransferServiceScannerDelegate?
init(delegate: TransferServiceScannerDelegate?) {
self.delegate = delegate
super.init()
}
override init() {
super.init()
}
}
class CentralViewController: UIViewController,
TransferServiceScannerDelegate {
var scanner: TransferServiceScanner = TransferServiceScanner()
func didStartScan(){}
func didStopScan(){}
func didTransferData(data: NSData?){}
override func viewDidLoad() {
super.viewDidLoad()
scanner.delegate = self
}
}
I tried implementing the NSWindowRestoration protocol in Swift, in a non-document-based application. However, the method restoreWindowWithIdentifier is never called at application launch. Can anyone point out my mistake?
Here is a subset of the code (which compiles and runs fine):
class AppDelegate: NSObject, NSApplicationDelegate, NSWindowRestoration {
var windowController : MyWindowController?
func applicationDidFinishLaunching(aNotification: NSNotification?) {
windowController = MyWindowController(windowNibName:"ImageSequenceView")
}
class func restoreWindowWithIdentifier(identifier: String!, state: NSCoder!, completionHandler: ((NSWindow!,NSError!) -> Void)!) {
NSLog("restoreWindowWithIdentifier: \(identifier), state: \(state)")
}
}
class MyWindowController: NSWindowController {
override func windowDidLoad() {
super.windowDidLoad();
window.restorationClass = AppDelegate.self
}
}
Thanks in advance!
You need to set a restoration class and also an identifier:
class MyWindowController: NSWindowController {
override func windowDidLoad() {
super.windowDidLoad()
self.window?.restorationClass = type(of: self)
self.window?.identifier = "MyWindow"
}
}
extension MyWindowController: NSWindowRestoration {
static func restoreWindow(withIdentifier identifier: String, state: NSCoder, completionHandler: #escaping (NSWindow?, Error?) -> Void) {
if identifier == "MyWindow" {
// Restore the window here
}
}
}
Of course you can also let another class restore the window, like you tried. You need to assign AppDelegate.self as the restorationClass in that case.
Also, be aware that the window restoration setting now defaults to "off", for whatever stupid reason.
How does one go about making a delegate, i.e. NSUserNotificationCenterDelegate in swift?
Here's a little help on delegates between two view controllers:
Step 1: Make a protocol in the UIViewController that you will be removing/will be sending the data.
protocol FooTwoViewControllerDelegate:class {
func myVCDidFinish(_ controller: FooTwoViewController, text: String)
}
Step2: Declare the delegate in the sending class (i.e. UIViewcontroller)
class FooTwoViewController: UIViewController {
weak var delegate: FooTwoViewControllerDelegate?
[snip...]
}
Step3: Use the delegate in a class method to send the data to the receiving method, which is any method that adopts the protocol.
#IBAction func saveColor(_ sender: UIBarButtonItem) {
delegate?.myVCDidFinish(self, text: colorLabel.text) //assuming the delegate is assigned otherwise error
}
Step 4: Adopt the protocol in the receiving class
class ViewController: UIViewController, FooTwoViewControllerDelegate {
Step 5: Implement the delegate method
func myVCDidFinish(_ controller: FooTwoViewController, text: String) {
colorLabel.text = "The Color is " + text
controller.navigationController.popViewController(animated: true)
}
Step 6: Set the delegate in the prepareForSegue:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "mySegue" {
let vc = segue.destination as! FooTwoViewController
vc.colorString = colorLabel.text
vc.delegate = self
}
}
And that should work. This is of course just code fragments, but should give you the idea. For a long explanation of this code you can go over to my blog entry here:
segues and delegates
If you are interested in what's going on under the hood with a delegate I did write on that here:
under the hood with delegates
Delegates always confused me until I realized that a delegate is just a class that does some work for another class. It's like having someone else there to do all the dirty work for you that you don't want to do yourself.
I wrote a little story to illustrate this. Read it in a Playground if you like.
Once upon a time...
// MARK: Background to the story
// A protocol is like a list of rules that need to be followed.
protocol OlderSiblingDelegate: class {
// The following command (ie, method) must be obeyed by any
// underling (ie, delegate) of the older sibling.
func getYourNiceOlderSiblingAGlassOfWater()
}
// MARK: Characters in the story
class BossyBigBrother {
// I can make whichever little sibling is around at
// the time be my delegate (ie, slave)
weak var delegate: OlderSiblingDelegate?
func tellSomebodyToGetMeSomeWater() {
// The delegate is optional because even though
// I'm thirsty, there might not be anyone nearby
// that I can boss around.
delegate?.getYourNiceOlderSiblingAGlassOfWater()
}
}
// Poor little sisters have to follow (or at least acknowledge)
// their older sibling's rules (ie, protocol)
class PoorLittleSister: OlderSiblingDelegate {
func getYourNiceOlderSiblingAGlassOfWater() {
// Little sis follows the letter of the law (ie, protocol),
// but no one said exactly how she had to respond.
print("Go get it yourself!")
}
}
// MARK: The Story
// Big bro is laying on the couch watching basketball on TV.
let bigBro = BossyBigBrother()
// He has a little sister named Sally.
let sally = PoorLittleSister()
// Sally walks into the room. How convenient! Now big bro
// has someone there to boss around.
bigBro.delegate = sally
// So he tells her to get him some water.
bigBro.tellSomebodyToGetMeSomeWater()
// Unfortunately no one lived happily ever after...
// The end.
In review, there are three key parts to making and using the delegate pattern.
the protocol that defines what the worker needs to do
the boss class that has a delegate variable, which it uses to tell the worker class what to do
the worker class that adopts the protocol and does what is required
Real life
In comparison to our Bossy Big Brother story above, delegates are often used for the following practical applications:
Communication: one class needs to send some information to another class.
Code example 1: sending data from one view controller to another
Code example 2: sending text input from a custom keyboard to a text field
Customization: one class wants to allow another class to customize it.
The great part is that these classes don't need to know anything about each other beforehand except that the delegate class conforms to the required protocol.
I highly recommend reading the following two articles. They helped me understand delegates even better than the documentation did.
What is Delegation? – A Swift Developer’s Guide
How Delegation Works – A Swift Developer’s Guide
One more note
Delegates that reference other classes that they do not own should use the weak keyword to avoid strong reference cycles. See this answer for more details.
It is not that different from obj-c.
First, you have to specify the protocol in your class declaration, like following:
class MyClass: NSUserNotificationCenterDelegate
The implementation will look like following:
// NSUserNotificationCenterDelegate implementation
func userNotificationCenter(center: NSUserNotificationCenter, didDeliverNotification notification: NSUserNotification) {
//implementation
}
func userNotificationCenter(center: NSUserNotificationCenter, didActivateNotification notification: NSUserNotification) {
//implementation
}
func userNotificationCenter(center: NSUserNotificationCenter, shouldPresentNotification notification: NSUserNotification) -> Bool {
//implementation
return true
}
Of course, you have to set the delegate. For example:
NSUserNotificationCenter.defaultUserNotificationCenter().delegate = self;
I got few corrections to post of #MakeAppPie
First at all when you are creating delegate protocol it should conform to Class protocol. Like in example below.
protocol ProtocolDelegate: class {
func myMethod(controller:ViewController, text:String)
}
Second, your delegate should be weak to avoid retain cycle.
class ViewController: UIViewController {
weak var delegate: ProtocolDelegate?
}
Last, you're safe because your protocol is an optional value. That means its "nil" message will be not send to this property. It's similar to conditional statement with respondToselector in objC but here you have everything in one line:
if ([self.delegate respondsToSelector:#selector(myMethod:text:)]) {
[self.delegate myMethod:self text:#"you Text"];
}
Above you have an obj-C example and below you have Swift example of how it looks.
delegate?.myMethod(self, text:"your Text")
Here's a gist I put together. I was wondering the same and this helped improve my understanding. Open this up in an Xcode Playground to see what's going on.
protocol YelpRequestDelegate {
func getYelpData() -> AnyObject
func processYelpData(data: NSData) -> NSData
}
class YelpAPI {
var delegate: YelpRequestDelegate?
func getData() {
println("data being retrieved...")
let data: AnyObject? = delegate?.getYelpData()
}
func processYelpData(data: NSData) {
println("data being processed...")
let data = delegate?.processYelpData(data)
}
}
class Controller: YelpRequestDelegate {
init() {
var yelpAPI = YelpAPI()
yelpAPI.delegate = self
yelpAPI.getData()
}
func getYelpData() -> AnyObject {
println("getYelpData called")
return NSData()
}
func processYelpData(data: NSData) -> NSData {
println("processYelpData called")
return NSData()
}
}
var controller = Controller()
DELEGATES IN SWIFT 2
I am explaining with example of Delegate with two viewControllers.In this case, SecondVC Object is sending data back to first View Controller.
Class with Protocol Declaration
protocol getDataDelegate {
func getDataFromAnotherVC(temp: String)
}
import UIKit
class SecondVC: UIViewController {
var delegateCustom : getDataDelegate?
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func backToMainVC(sender: AnyObject) {
//calling method defined in first View Controller with Object
self.delegateCustom?.getDataFromAnotherVC(temp: "I am sending data from second controller to first view controller.Its my first delegate example. I am done with custom delegates.")
self.navigationController?.popViewControllerAnimated(true)
}
}
In First ViewController Protocol conforming is done here:
class ViewController: UIViewController, getDataDelegate
Protocol method definition in First View Controller(ViewController)
func getDataFromAnotherVC(temp : String)
{
// dataString from SecondVC
lblForData.text = dataString
}
During push the SecondVC from First View Controller (ViewController)
let objectPush = SecondVC()
objectPush.delegateCustom = self
self.navigationController.pushViewController(objectPush, animated: true)
First class:
protocol NetworkServiceDelegate: class {
func didCompleteRequest(result: String)
}
class NetworkService: NSObject {
weak var delegate: NetworkServiceDelegate?
func fetchDataFromURL(url : String) {
delegate?.didCompleteRequest(result: url)
}
}
Second class:
class ViewController: UIViewController, NetworkServiceDelegate {
let network = NetworkService()
override func viewDidLoad() {
super.viewDidLoad()
network.delegate = self
network.fetchDataFromURL(url: "Success!")
}
func didCompleteRequest(result: String) {
print(result)
}
}
Very easy step by step (100% working and tested)
step1: Create method on first view controller
func updateProcessStatus(isCompleted : Bool){
if isCompleted{
self.labelStatus.text = "Process is completed"
}else{
self.labelStatus.text = "Process is in progress"
}
}
step2: Set delegate while push to second view controller
#IBAction func buttonAction(_ sender: Any) {
let secondViewController = self.storyboard?.instantiateViewController(withIdentifier: "secondViewController") as! secondViewController
secondViewController.delegate = self
self.navigationController?.pushViewController(secondViewController, animated: true)
}
step3: set delegate like
class ViewController: UIViewController,ProcessStatusDelegate {
step4: Create protocol
protocol ProcessStatusDelegate:NSObjectProtocol{
func updateProcessStatus(isCompleted : Bool)
}
step5: take a variable
var delegate:ProcessStatusDelegate?
step6: While go back to previous view controller call delegate method so first view controller notify with data
#IBAction func buttonActionBack(_ sender: Any) {
delegate?.updateProcessStatus(isCompleted: true)
self.navigationController?.popViewController(animated: true)
}
#IBAction func buttonProgress(_ sender: Any) {
delegate?.updateProcessStatus(isCompleted: false)
self.navigationController?.popViewController(animated: true)
}
Simple Example:
protocol Work: class {
func doSomething()
}
class Manager {
weak var delegate: Work?
func passAlong() {
delegate?.doSomething()
}
}
class Employee: Work {
func doSomething() {
print("Working on it")
}
}
let manager = Manager()
let developer = Employee()
manager.delegate = developer
manager.passAlong() // PRINTS: Working on it
Delegates are a design pattern that allows one object to send messages to another object when a specific event happens.
Imagine an object A calls an object B to perform an action. Once the action is complete, object A should know that B has completed the task and take necessary action, this can be achieved with the help of delegates!
Here is a tutorial implementing delegates step by step in swift 3
Tutorial Link
Here is real life delegate scenario
Lets make our own UITextField and UITextFieldDelegate
// THE MYSTERIOUS UITEXTFIELD
protocol UITextFieldDelegate {
func textFieldDidChange(_ textField: UITextField) -> Void
}
class UITextField {
var delegate: UITextFieldDelegate?
private var mText: String?
var text: String? {
get {
return mText
}
}
init(text: String) {
}
init() {
}
func setText(_ text: String) {
mText = text
delegate?.textFieldDidChange(self)
}
}
// HERE IS MY APP
class Main {
let textfield = UITextField()
func viewDidLoad() {
print("viewDidLoad")
textfield.delegate = self
textfield.setText("Hello")
}
}
extension Main: UITextFieldDelegate {
func textFieldDidChange(_ textField: UITextField) {
print(textField.text ?? "No string")
}
}
let main = Main()
main.viewDidLoad()
Here Simple Code Example of Delegate:
//MARK: - Protocol ShowResult
protocol ShowResult: AnyObject {
func show(value: Int)
}
//MARK: - MyOperation Class
class MyOperation {
weak var delegate: ShowResult?
func sum(fNumber: Int, sNumber: Int) {
delegate?.show(value: fNumber + sNumber)
}
}
//MARK: - ViewController Class
class ViewController: UIViewController,ShowResult {
var myOperation: MyOperation?
override func viewDidLoad() {
super.viewDidLoad()
loadMyOperation()
myOperation?.delegate = self
myOperation?.sum(fNumber: 100, sNumber: 20)
}
private func loadMyOperation() {
if myOperation == nil {
myOperation = MyOperation()
}
}
func show(value: Int) {
print("value: \(value)")
}
}
The solutions above seemed a little coupled and at the same time avoid reuse the same protocol in other controllers, that's why I've come with the solution that is more strong typed using generic type-erasure.
#noreturn public func notImplemented(){
fatalError("not implemented yet")
}
public protocol DataChangedProtocol: class{
typealias DataType
func onChange(t:DataType)
}
class AbstractDataChangedWrapper<DataType> : DataChangedProtocol{
func onChange(t: DataType) {
notImplemented()
}
}
class AnyDataChangedWrapper<T: DataChangedProtocol> : AbstractDataChangedWrapper<T.DataType>{
var base: T
init(_ base: T ){
self.base = base
}
override func onChange(t: T.DataType) {
base.onChange(t)
}
}
class AnyDataChangedProtocol<DataType> : DataChangedProtocol{
var base: AbstractDataChangedWrapper<DataType>
init<S: DataChangedProtocol where S.DataType == DataType>(_ s: S){
self.base = AnyDataChangedWrapper(s)
}
func onChange(t: DataType) {
base.onChange(t)
}
}
class Source : DataChangedProtocol {
func onChange(data: String) {
print( "got new value \(data)" )
}
}
class Target {
var delegate: AnyDataChangedProtocol<String>?
func reportChange(data:String ){
delegate?.onChange(data)
}
}
var source = Source()
var target = Target()
target.delegate = AnyDataChangedProtocol(source)
target.reportChange("newValue")
output: got new value newValue
In swift 4.0
Create a delegate on class that need to send some data or provide some functionality to other classes
Like
protocol GetGameStatus {
var score: score { get }
func getPlayerDetails()
}
After that in the class that going to confirm to this delegate
class SnakesAndLadders: GetGameStatus {
func getPlayerDetails() {
}
}
In swift 5
I am a beginner, I think this is easiest way to understand in practical scenario
Note:Any improvisations are most appreciated
protocol APIService {
func onSuccessResponse() -> AnyObject
func onFailureResponse() -> AnyObject
}
class APIHelper{
var delegate : APIService?
func postUsersDataAPI() {
//assuming API communication is success
if(success){
let _: AnyObject? = delegate?.onSuccessResponse()
}else if(failure){
let _: AnyObject? = delegate?.onFailureResponse()
}
}
func getAllUsersAPI() {
//assuming API communication is success
if(success){
let _: AnyObject? = delegate?.onSuccessResponse()
}else if(failure){
let _: AnyObject? = delegate?.onFailureResponse()
}
}
}
class ViewController:UIViewController,APIService {
func onSuccessResponse() -> AnyObject {
print("onSuccessResponse") as AnyObject
}
func onFailureResponse() -> AnyObject {
print("onFailureResponse") as AnyObject
}
#IBAction func clickBtnToPostUserData(_ sender: Any) {
let apiHelper = APIHelper()
apiHelper.delegate = self
apiHelper.postAPI()
}