I am trying to understand delegate and I don't get why it says that I have used unresolved identifier 'data'.
//This is my sendingVC
import UIKit
protocol TextFieldDelegate {
func userEnteredText(text: String)
}
class ViewController: UIViewController {
#IBOutlet weak var textField: UITextField!
var delegate: TextFieldDelegate? = nil
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func sendButton(_ sender: AnyObject) {
if delegate != nil {
if textField.text != nil {
let data = textField.text
delegate?.userEnteredText(text: data!)
}
}
}
}
The problem is with this code below for my receivingVC I am not able to accesss data variable which should be passed by the delegate.
//This is my receivingVC
import UIKit
class SecondViewController: UIViewController, TextFieldDelegate {
#IBOutlet weak var label: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
func userEnteredText(text: String) {
label.text = data // Use of unresolved identifier 'data'
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "sendSegue" {
let destVC: ViewController = segue.destination as! ViewController
destVC.delegate = self
}
}
}
Update your code:
func userEnteredText(text: String) {
label.text = text
}
Related
I'm building a simple dictionary app. I've gotten it to display words on UItableView while user is searching or not. I'm working on assigning each individual word with its own definition but I'm facing a trouble while setting the destination for each word at words array.
Here is part of my ViewController class and its contents:
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var searchBar: UISearchBar!
#IBOutlet weak var tableView: UITableView!
var wordSearch = [String]()
var wordArray: [String] = []
var searching = false
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
let url = Bundle.main.url(forResource: "zo_words", withExtension: "txt")! // file URL for file "words_alpha.txt"
do {
let string = try String(contentsOf: url, encoding: .utf8)
wordArray = string.components(separatedBy: "\n")
} catch {
print(error)
}
}
}
extension ViewController: UITableViewDataSource, UITableViewDelegate {
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if searching {
return wordSearch.count
} else {
return wordArray.count
}
Here is my wordSearch function:
extension ViewController: UISearchBarDelegate {
func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
wordSearch = wordArray.filter({$0.lowercased().prefix(searchText.count) == searchText.lowercased();})
searching = true
tableView.reloadData()
}
Cannot assign value of type 'String' to type 'ViewController' Error is raised in below function while building
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destination = segue.destination as? DefinitionViewController {
destination.word = wordArray[(tableView.indexPathForSelectedRow?.row)!]
class DefinitionViewController:
import UIKit
class DefinitionViewController: UIViewController {
#IBOutlet weak var lbDefinition:
UILabel!
var word: ViewController?
override func viewDidLoad() {
super.viewDidLoad()
lbDefinition.text = "\((word?.wordSearch)!)"
}
}
I think it's not applicable and recommended to take an instance from the ViewController but you can do it so easy by using the below:
Let's say you've word in your viewControllerthen you have to do the below:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
guard tableView.indexPathForSelectedRow != nil else {
return
}
let selectedWord = wordArray[tableView.indexPathForSelectedRow!.row]
let destination = segue.destination as! DefinitionViewController
destination.word = selectedWord
}
DefinitionViewController:
import UIKit
class DefinitionViewController: UIViewController {
#IBOutlet weak var lbDefinition:
UILabel!
var word: String?
override func viewDidLoad() {
super.viewDidLoad()
guard word != nil else {return}
lbDefinition.text = "\((word?.wordSearch)!)"
}
}
class ViewController: UIViewController {
static var wordSearch = [string]()
}
class DefinitionViewController: UIViewController {
#IBOutlet weak var lbDefinition:UILabel!
override func viewDidLoad() {
super.viewDidLoad()
lbDefinition.text = "\(ViewController.wordSearch)"
}
}
how do you pass data from search Bar to UILabel in a different view controller
Passing Data between View Controllers
I have tried multiple questions here on stack, but it just doesn't work or the simulator ends up crashing for me
class FirstVC: UIViewController, DataEnteredDelegate {
#IBOutlet weak var label: UILabel!
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "showSecondViewController" {
let secondViewController = segue.destination as! SecondVC
secondViewController.delegate = self
}
}
func userDidEnterInformation(info: String) {
label.text = info
}
}
// protocol used for sending data back
protocol DataEnteredDelegate: class {
func userDidEnterInformation(info: String)
}
class SecondVC: UIViewController {
// making this a weak variable so that it won't create a strong reference cycle
weak var delegate: DataEnteredDelegate? = nil
#IBOutlet weak var searchBar: UISearchBar!
#IBAction func sendTextBackButton(sender: AnyObject) {
// call this method on whichever class implements our delegate protocol
delegate?.userDidEnterInformation(info: searchBar.text!)
// go back to the previous view controller
_ = self.navigationController?.popViewController(animated: true)
}
}
I don't find anything suspicious in your code which cause app crash. Meanwhile for data transfer between view controller we can use delegation and NotificationCenter. Below code uses NotificationCenter
let kStringTransfer = "StringTransferNotification"
class FirstViewController: UIViewController, DataEnteredDelegate {
#IBOutlet weak var textField: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(setString(notify:)), name: NSNotification.Name(rawValue: kStringTransfer), object: nil)
}
func getSecondVC() {
if let second = self.storyboard?.instantiateViewController(withIdentifier: "Second") as? ViewController {
self.navigationController?.pushViewController(second, animated: true)
}
}
#IBAction func searchBarBtn(_ sender: Any) {
//go to search view controller
getSecondVC()
}
#objc func setString(notify: Notification) {
//set search bar string to text field
textField.text = notify.object as? String
}
}
class SecondViewController: UIViewController, UISearchBarDelegate {
#IBOutlet weak var searchBar: UISearchBar!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
searchBar.delegate = self
}
#IBAction func goBackBtn(_ sender: Any) {
NotificationCenter.default.post(name: NSNotification.Name(rawValue: kStringTransfer), object: searchBar.text)
self.navigationController?.popViewController(animated: true)
}
}
When I need pass just small values between 2 viewControllers, I don't use a delegate, just create a variable in second view and pass like this.
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if (segue.identifier == "showView") {
let vc = segue.destination as! secondViewController
vc.stringTemp = "My string"
}
}
I am completely new to Swift programming and tried to delegate a single String from one ViewController to another by clicking a send button. The problem is , that it does not work ...
I guess it would be easy for you to solve this and considering that it would be very helpful wether you explain me what I did wrong. :)
Thank you a lot
import UIKit
protocol protoTYdelegate {
func didSendMessage(message: String)
}
class New: UIViewController {
#IBOutlet weak var SendButton: UIButton!
var tydelegate: protoTYdelegate?
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func SendButtonAction(_ sender: Any) {
let nachricht = "It works fine."
tydelegate?.didSendMessage(message: nachricht)
}
}
import UIKit
class ThankYouPage: UIViewController {
#IBOutlet weak var numbersView: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
let controller = New()
controller.tydelegate = self
}
}
extension ThankYouPage: protoTYdelegate{
func didSendMessage(message: String) {
numbersView.text = message
}
As far as I understand, this code block doesn't work but the problem is not in the code, it's actually way that you choose to send data. In iOS development, there are many ways to send data. In your case, you need to use prepareForSegue method to send data to new class, not necessary to use delegates.
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if (segue.identifier == "ThankYouPage") {
let vc = segue.destination as! ThankYouPage
vc.message = "Message that you want to send"
}
}
And you need to implement your ThankYouPage as:
class ThankYouPage: UIViewController {
#IBOutlet weak var numbersView: UILabel!
var message = ""
override func viewDidLoad() {
super.viewDidLoad()
numbersView.text = message
}
}
In addition to that, you can use didSet method to print out the message to label instead of printing it directly in viewDidLoad method. Simply:
class ThankYouPage: UIViewController {
#IBOutlet weak var numbersView: UILabel!
var message: String?{
didSet{
numbersView.text = message
}
}
override func viewDidLoad() {
super.viewDidLoad()
}
}
I hope this helps you.
#Eyup Göymen's answer is right.
I have another way, assuming that you are not using segue and you are pushing to next controller by manual-code.
So your ThankYouPage code should be like :
import UIKit
class ThankYouPage: UIViewController {
#IBOutlet weak var numbersView: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func someButtonAction(_ sender: Any) { // By clicking on some, you are opening that `New` controller
let detailView = self.storyboard?.instantiateViewController(withIdentifier: "New") as! New
detailView.tydelegate = self
self.navigationController?.pushViewController(detailView, animated: true)
}
}
extension ThankYouPage: protoTYdelegate {
func didSendMessage(message: String) {
numbersView.text = message
}
}
I want to the image thats in my UIImageView on my previous View after I tap on a button.
Any help? Thanks.
MainViewController.swift
class MainViewController: UIViewController {
#IBOutlet weak var hatBackground: UIImageView!
override func viewDidLoad() {
super.viewDidLoad()
hatBackground.image = UIImage(named: "black-hat-front.jpg")
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "showPatches"{
if let childViewController = segue.destination as? ChildViewController{
}
}
}
}
ChildViewController.swift
class ChildViewController: UIViewController {
#IBOutlet weak var doubleCupButton: UIButton!
override func viewDidLoad() {
super.viewDidLoad()
self.title = "Choose a Patch"
}
#IBAction func doubleCupButtonPressed(_ sender: AnyObject) {
hatBackground.image = UIImage(named: "badgal-hat.jpg")??
// Go back to previous Controller
navigationController?.popViewController(animated: true)
}
}
If I good understood , you want choose image in ChildViewController and show it in MainViewController. To do that you should implement delegate pattern like this:
MainViewController
class MainViewController: UIViewController, ChildViewControllerDelegate {
#IBOutlet weak var hatBackground: UIImageView!
override func viewDidLoad() {
super.viewDidLoad()
hatBackground.image = UIImage(named: "black-hat-front.jpg")
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "showPatches"{
if let childViewController = segue.destination as? ChildViewController{
childViewController.delegate = self
}
}
}
func didSelectImage(image: UIImage?) {
self.hatBackground.image = image
}
}
ChildViewController
class ChildViewController: UIViewController {
#IBOutlet weak var doubleCupButton: UIButton!
var delegate: ChildViewControllerDelegate?
override func viewDidLoad() {
super.viewDidLoad()
self.title = "Choose a Patch"
}
#IBAction func doubleCupButtonPressed(_ sender: AnyObject) {
let selectedImage = UIImage(named: "badgal-hat.jpg")
delegate?.didSelectImage(image: selectedImage)
self.navigationController?.popViewController(animated: true)
}
}
ChildViewControllerDelegate
protocol ChildViewControllerDelegate {
func didSelectImage(image:UIImage?)
}
My code is below. When I press the 'Done' or 'Cancel' buttons, it doesn't work as I want. I did some debugging, and delegate is nil even though I set it. Please help - thanks.
class ViewController: UIViewController,EditViewControllerDelegate {
#IBOutlet weak var label: UILabel!
//页面跳转时
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "EditView" {
//通过seque的标识获得跳转目标
let controller = segue.destinationViewController as! EditViewController
//设置代理
controller.delegate = self
//将值传递给新页面
controller.oldInfo = label.text
}
}
func editInfo(controller:EditViewController, newInfo:String){
label.text = newInfo
//关闭编辑页面
controller.presentingViewController!.dismissViewControllerAnimated(true, completion: nil)
}
func editInfoDidCancer(controller:EditViewController){
//关闭编辑页面
controller.presentingViewController!.dismissViewControllerAnimated(true, completion: nil)
}
}
import UIKit
protocol EditViewControllerDelegate {
func editInfo(controller:EditViewController, newInfo:String)
func editInfoDidCancer(controller:EditViewController)
}
class EditViewController: UIViewController {
#IBOutlet weak var textField: UITextField!
var delegate:EditViewControllerDelegate?
var oldInfo:String?
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
if oldInfo != nil{
textField.text = oldInfo
}
}
#IBAction func done(sender: AnyObject) {
delegate?.editInfo(self, newInfo: textField.text!)
}
#IBAction func cancel(sender: AnyObject) {
delegate?.editInfoDidCancer(self)
}
}
Try this,
class ViewController: UIViewController,EditViewControllerDelegate {
var controller: EditViewController?
#IBOutlet weak var label: UILabel!
//页面跳转时
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "EditView" {
//通过seque的标识获得跳转目标
controller = segue.destinationViewController as! EditViewController
//设置代理
controller.delegate = self
//将值传递给新页面
controller.oldInfo = label.text
}
}
func editInfo(controller:EditViewController, newInfo:String){
label.text = newInfo
//关闭编辑页面
controller.presentingViewController!.dismissViewControllerAnimated(true, completion: nil)
}
func editInfoDidCancer(controller:EditViewController){
//关闭编辑页面
controller.presentingViewController!.dismissViewControllerAnimated(true, completion: nil)
}
}
import UIKit
protocol EditViewControllerDelegate {
func editInfo(controller:EditViewController, newInfo:String)
func editInfoDidCancer(controller:EditViewController)
}
class EditViewController: UIViewController {
#IBOutlet weak var textField: UITextField!
var delegate:EditViewControllerDelegate?
var oldInfo:String?
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
if oldInfo != nil{
textField.text = oldInfo
}
}
#IBAction func done(sender: AnyObject) {
delegate?.editInfo(self, newInfo: textField.text!)
}
#IBAction func cancel(sender: AnyObject) {
delegate?.editInfoDidCancer(self)
}
}
I’m not able to tell from your code how you are handling the opening of EditViewController from your ViewController.
I’m guessing that your prepareForSegue:sender: is not getting called resulting in the delegate not getting set. To fix this, you will need to add a performSegueWithIdentifier:sender: call at the point where the segue needs to happen as in
self.performSegueWithIdentifier("EditView", sender: self)
You should replace whatever code is performing the opening of EditViewController with that call.
I have an app the uses showViewController:sender: to open up a second view controller from the first one even though there is a Show segue defined in my storyboard. The segue in my storyboard doesn’t get used in that case and prepareForSegue:sender: is never called as a result.
If I replace my
showViewController(myVC, sender: self)
with
performSegueWithIdentifier("mySegue", sender: self)
then prepareForSegue:sender: will get called. If I am setting a delegate, like you are, in prepareForSegue:sender:, the delegate will get set before the segue happens.