I have a table on which a cell is made using .xib. There are two views on this cell. When I click on each view, and I set the image and title for another viewController. I made a protocol for this, but I just can’t get this data on another viewController because my delegate = nil.
In this class, I set properties.
сlass DataTableViewCell: UITableViewCell {
var dataDelegete: DataAccountCellDelegete? = nil
#objc func accountViewTaped() {
dataDelegete?.navigationBarIcon(image: UIImage(named: "icon") ?? UIImage())
dataDelegete?.navigationBarTitle(title: "title")
}
#objc func settingsViewTaped() {
dataDelegete?.navigationBarIcon(image: UIImage(named: "icon") ?? UIImage())
dataDelegete?.navigationBarTitle(title: "title")
}
}
protocol DataAccountCellDelegete {
func navigationBarIcon(image: UIImage)
func navigationBarTitle(title: String)
}
In this class, I get and want to set these properties, but my delegate = nil
class AccountViewController: UIViewController {
var dataVC = DataTableViewCell()
override func viewDidLoad() {
super.viewDidLoad()
dataVC.delegete = self
}
}
extension AccountViewController: DataAccountCellDelegete{
func menuNavigationBarIcon(image: UIImage) {
menuNavigationBar.addImage(image)
}
func menuNavigationBarTitle(title: String) {
menuNavigationBar.addTitle(title)
}
}
How do I declare a delegate correctly?
The view hierarchy should be like
ViewController -> TableView -> TableViewCell
So, ViewController has the reference of TableView & TableView has the reference of the cell. So the data passing should be reversed.
TableViewCell -> TableView -> ViewController
as vadian said ,Cells are reused and being created in cellForRowAt. The variable dataVC is useless here.
Related
I'm creating a quiz app with custom cells that include a label of questions and then an answer coming from a UISegmentedControl.
The values of the segmentedcontrols get changed when scrolling and this leads to an inaccurate score. I understand that this is due to UITableView reusing cells.
My tableview's datasource in my main vc is simply the labels for all my questions coming from a plist file.
The code for my custom tableviewcell class is
class QuestionsTableViewCell: UITableViewCell {
#IBOutlet weak var questionLabel: UILabel!
#IBOutlet weak var selection: UISegmentedControl!
var question: String = "" {
didSet {
if (question != oldValue) {
questionLabel.text = question
}
}
}
override func awakeFromNib() {
super.awakeFromNib()
// Initialization code
}
override func setSelected(_ selected: Bool, animated: Bool) {
super.setSelected(selected, animated: animated)
// Configure the view for the selected state
}
//Just for testing
#IBAction func segmentChanged(_ sender: UISegmentedControl) {
print("value is ", sender.selectedSegmentIndex);
}
}
where the View is stored in an .XIB file.
And the code for my main vc is
class ViewController: UIViewController, UITableViewDataSource {
let questionsTableIdentifier = "QuestionsTableIdentifier"
#IBOutlet var tableView:UITableView!
var questionsArray = [String]();
var questionsCellArray = [QuestionsTableViewCell]();
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
let path = Bundle.main.path(forResource:
"Questions", ofType: "plist")
questionsArray = NSArray(contentsOfFile: path!) as! [String]
tableView.register(QuestionsTableViewCell.self,
forCellReuseIdentifier: questionsTableIdentifier)
let xib = UINib(nibName: "QuestionsTableViewCell", bundle: nil)
tableView.register(xib,
forCellReuseIdentifier: questionsTableIdentifier)
tableView.rowHeight = 108;
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return questionsArray.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(
withIdentifier: questionsTableIdentifier, for: indexPath)
as! QuestionsTableViewCell
let rowData = questionsArray[indexPath.row]
cell.question = rowData
return cell
}
#IBAction func calculate(_ sender: UIButton) {
var score = 0
for cell in tableView.visibleCells as! [QuestionsTableViewCell] {
score += cell.selection.selectedSegmentIndex
}
let msg = "Score is, \(score)"
print(msg)
}
#IBAction func reset(_ sender: UIButton) {
for cell in tableView.visibleCells as! [QuestionsTableViewCell] {
cell.selection.selectedSegmentIndex = 0;
}
}
}
What I'd like to do is just keep track of all 'selection' changes of the Questions cells in an array, and then use that array in cellForRowAt. I'm just confused as to how i can dynamically keep track of changes from a view in another class. I'm new to Swift and would like to solve this is a proper MVC fashion. Thanks
Instead of a simple string array as data source create a class holding the text and the selected index
class Question {
let text : String
var answerIndex : Int
init(text : String, answerIndex : Int = 0) {
self.text = text
self.answerIndex = answerIndex
}
}
Declare questionArray as
var questions = [Question]()
Populate the array in viewDidLoad with
let url = Bundle.main.url(forResource: "Questions", withExtension: "plist")!
let data = try! Data(contentsOf: url)
let questionsArray = try! PropertyListSerialization.propertyList(from: data, format: nil) as! [String]
questions = questionsArray.map {Question(text: $0)}
In the custom cell add a callback and call it in the segmentChanged method passing the selected index, the property question is not needed, the label is updated in cellForRow of the controller
class QuestionsTableViewCell: UITableViewCell {
#IBOutlet weak var questionLabel: UILabel!
#IBOutlet weak var selection: UISegmentedControl!
var callback : ((Int) -> ())?
#IBAction func segmentChanged(_ sender: UISegmentedControl) {
print("value is ", sender.selectedSegmentIndex)
callback?(sender.selectedSegmentIndex)
}
}
In cellForRow add the callback and update the model in the closure
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: questionsTableIdentifier, for: indexPath) as! QuestionsTableViewCell
let question = questions[indexPath.row]
cell.questionLabel.text = question.text
cell.selection.selectedSegmentIndex = question.answerIndex
cell.callback = { index in
question.answerIndex = index
}
return cell
}
To reset the segmented controls in the cells set the property in the model to 0 and reload the table view
#IBAction func reset(_ sender: UIButton) {
questions.forEach { $0.answerIndex = 0 }
self.tableView.reloadData()
}
Now you could calculate the score directly from the model instead of the view.
Don't try to use cells to hold information. As the user scrolls through your table view, cells that scroll out of view will get recycled and their field settings will be lost. Also, newly dequeued cells will have the settings from the last time they were used.
You need to refactor your code to read/write information into a data model. Using an array of Structs as a data model is a reasonable way to go. (Or, as vadian suggests in his answer, and array of Class objects, so you get reference semantics.)
You have an IBAction segmentChanged() in your custom cell class. The next trick is to notify the view controller when the user changes the selection, and to update cells when you set them up in cellForRowAt.
I suggest defining a protocol QuestionsTableViewCellProtocol, and have the view controller conform to that protocol:
protocol QuestionsTableViewCellProtocol {
func userSelected(segmentIndex: Int, inCell cell: UITableViewCell)
}
}
Add a delegate property to your QuestionsTableViewCell class:
class QuestionsTableViewCell: UITableViewCell {
weak var delegate: QuestionsTableViewCellProtocol?
//The rest of your class goes here...
}
Update your cell's segmentChanged() method to invoke the delegate's userSelected(segmentIndex:inCell:) method.
In your view controller's cellForRowAt, set the cell's delegate to self.
func userSelected(segmentIndex: Int, inCellCell cell: UITableViewCell) {
let indexPath = tableView.indexPath(for: cell)
let row = indexPath.row
//The code below assumes that you have an array of structs, `dataModel`, that
//has a property selectedIndex that remembers which cell is selected.
//Adjust the code below to match your actual array that keeps track of your data.
dataModel[row].selectedIndex = segmentIndex
}
Then update cellforRowAt() to use the data model to set the segment index on the newly dequeued cell to the correct index.
Also update your calculate() function to look at the values in your dataModel to calculate the score, NOT the tableView.
That's a rough idea. I left some details out as "an exercise for the reader." See if you can figure out how to make that work.
i need an help, see this class
import UIKit
protocol TypesTableViewControllerDelegate: class {
func typesController(controller: TypesTableViewController, didSelectTypes types: [String])
}
class TypesTableViewController: UITableViewController {
let possibleTypesDictionary = ["bakery":"Bakery", "bar":"Bar", "cafe":"Cafe", "grocery_or_supermarket":"Supermarket", "restaurant":"Restaurant"]
var selectedTypes: [String]!
weak var delegate: TypesTableViewControllerDelegate!
var sortedKeys: [String] {
return possibleTypesDictionary.keys.sort()
}
// MARK: - Actions
#IBAction func donePressed(sender: AnyObject) {
delegate?.typesController(self, didSelectTypes: selectedTypes)
}
// MARK: - Table view data source
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return possibleTypesDictionary.count
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("TypeCell", forIndexPath: indexPath)
let key = sortedKeys[indexPath.row]
let type = possibleTypesDictionary[key]!
cell.textLabel?.text = type
cell.imageView?.image = UIImage(named: key)
cell.accessoryType = (selectedTypes!).contains(key) ? .Checkmark : .None
return cell
}
// MARK: - Table view delegate
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
tableView.deselectRowAtIndexPath(indexPath, animated: true)
let key = sortedKeys[indexPath.row]
if (selectedTypes!).contains(key) {
selectedTypes = selectedTypes.filter({$0 != key})
} else {
selectedTypes.append(key)
}
tableView.reloadData()
}
}
here the user can tap a cell of the tableView so that his prefer types are used on the next viewController for a search, now i need to build a class that do the same thing but there is no a tableview rather only 6 buttons in a view that the user can tap (so a viewController with only 6 different buttons to tap). The problem is that i don't know how to pass to the next viewController what buttons have been pressed and what are not, how can i build this class?
here is the function in the other class that need to know what buttons have been pressed
func fetchNearbyPlaces(coordinate: CLLocationCoordinate2D) {
mapView.clear()
dataProvider.fetchPlacesNearCoordinate(coordinate, radius:searchRadius, types: searchedTypes) { places in
for place: GooglePlace in places {
let marker = PlaceMarker(place: place)
marker.map = self.mapView
where is "types: serchedTypes"
What you wanna do is called delegation here is how you do it:
Make a protocol like this one:
protocol TransferProtocol : class
{
func transferData(types:[String])
}
Make the view controller with the buttons conform to that protocol, I like to do it by adding extensions to my classes like so:
extension ButtonsViewController:TransferProtocol{
func transferData(types:[String]){
//Do whatever you want here
}
}
Declare a variable in your Table View Controller class with the protocol you created as its type, this is called a delegate
weak var transferDelegate:TransferProtocol?
Before you segue to the Buttons View Controller you want to set that view controller as the delegate you just created like so:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let vc = segue.destination as? ButtonsViewController
transferDelegate = vc
vc?.transferData(types: selected)
}
If done correctly you should be able to work with the array you built in the Table View Controller(TypesTableViewController)
I have this in my storyboard.
ViewController -> Tableview -> Custom cell
the custom cell has inside a collection view.
Inside my ViewController i have some filter buttons that i want to filter the array data of the collection view and reload it also.
So I tried to make a delegate method with the following code
protocol ReloadTheDataDelegate: class {
func reloadTheCV()
}
class NearMeViewController: UIViewController {
weak var delegate: ReloadTheDataDelegate?
#IBAction func anAction(_sender : AnyObject){
requests.weekendEventData.sort() { $0.realDate < $1.realDate }
delegate?.reloadTheCV()
}
}
class WeekendTableViewCell: UITableViewCell, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource, UICollectionViewDelegate, ReloadTheDataDelegate {
#IBOutlet public weak var weekendCV: UICollectionView!
func reloadTheCV() {
print("done") //never printed
weekendCV.reloadData()
}
override func awakeFromNib() {
super.awakeFromNib()
if let myViewController = parentViewController as? NearMeViewController {
myViewController.delegate = self
}
weekendCV.register(UINib(nibName: "WeekendCollectionViewCell", bundle: nil),
forCellWithReuseIdentifier: "phoneweekendcell")
weekendCV.delegate = self
weekendCV.dataSource = self
}
}
And the extension that i take the ViewController
extension UIView {
var parentViewController: UIViewController? {
var parentResponder: UIResponder? = self
while parentResponder != nil {
parentResponder = parentResponder!.next
if let viewController = parentResponder as? UIViewController {
return viewController
}
}
return nil
}
}
Could anyone explain why the function reloadTheCV() is never called ?
NearMeViewController delegate (ReloadTheDataDelegate ) is nil. Due to that its not printing. You didn't set the delegate and this approach is too complex also.
So, Instead of approaching with protocol concept. Simply you can reload the cell's collection view with the following manner.
Add the following function on your NearMeViewController. And call whenever you need reload the collection view.
func reloadCellCV() {
for cell in tableView.visibleCells {
if let cell = cell as? WeekendTableViewCell {
DispatchQueue.main.async {
cell.weekendCV.reloadData()
}
}
}
}
Can anyone help me to give reason to use delegate/protocol oriented or get superview, as I know swift use protocol oriented on code but for grab parent view or controller we still can use get superview like
Get superview example:
extension UIView {
var parentViewController: UIViewController? {
var parentResponder: UIResponder? = self
while parentResponder != nil {
parentResponder = parentResponder!.next
if let viewController = parentResponder as? UIViewController {
return viewController
}
}
return nil
}
}
Use delegate example:
protocol SomeDelegate {
func didClick()
}
class Child {
var delegate: SomeDelegate?
}
What Pros and Cons to use delegate or get superview ?
Example for parentView:
class Cell {
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
self.parentViewController.view.makeToast("Something !")
}
}
Example for delegate:
class Parent: SomeDelegate {
func didClick() {
self.view.makeToast("Something !")
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableview.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as? Cell
cell.delegate = self
return cell
}
}
class Cell {
var label: UILabel
var delegate: SomeDelegate?
func configure() {
label.addGestureRecognizer(UILongPressGestureRecognizer(
target: self,
action: #selector(copyAction(_:))
))
}
#objc private func copyAction(_ sender: UILongPressGestureRecognizer) {
guard let delegate = self.delegate else {
return
}
delegate.didClick()
}
}
Delegate is preferred, not the superview. some reasons below
A view added in stack is not always retained in memory after its addition. especially when no strong reference maintained (this differs when view added from XIB or SB). So in this case calling superview might sometime crash with an unrecognized selector sent on some random instance.
One can create a view and never add to another view. ex for sake of removing you might comment just addsubview line leaving other code as is. At this time also the superview is nil.
Usage of custom views under uicontrols with own reusable view stack like Collectionview,TableView etc. would change superviews in runtime. so not always guaranteed to call same superview instance.
i edited my question , because set textfield maybe can't be simple, need references so this is my code, but still have issue :
this code for TableViewController :
import UIKit
protocol PaymentSelectionDelegate{
func userDidSelectPayment(title: NSString?)
}
class PopPaymentTableViewController: UITableViewController {
var delegate : PaymentSelectionDelegate!
override func viewDidLoad() {
super.viewDidLoad()
}
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath?) {
self.dismissViewControllerAnimated(true){
if self.delegate != nil{
if let ip = indexPath{
var payItem : PayMethod
payItem = self.myList[ip.row] as! PayMethod
var title = payItem.paymentName
self.delegate.userDidSelectPayment(title)
}
}
}
}
}
and for code TransactionViewController :
import UIKit
class TransactionViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate, PaymentSelectionDelegate, UITextFieldDelegate, UIPopoverPresentationControllerDelegate{
#IBOutlet var paymentTextField: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
}
func resign(){
paymentTextField.resignFirstResponder()
}
func textFieldShouldBeginEditing(textField: UITextField) -> Bool {
if (textField == paymentTextField){
resign()
performSegueWithIdentifier("seguePayment", sender: self)
}
}
func adaptivePresentationStyleForPresentationController(controller: UIPresentationController) -> UIModalPresentationStyle {
return .None
}
func userDidSelectPayment(title: NSString?) {
paymentTextField.text = title as! String
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "seguePayment"{
var VC = segue.destinationViewController as! UINavigationController
var controller = VC.popoverPresentationController
if controller != nil{
controller?.delegate = self
var paymentVC = PopPaymentTableViewController()
paymentVC.delegate = self
}
}
}
}
this issue is: variable delegate in TableViewController like seems always nil, so cant set value
NB : sorry i edited totally my question, because so many answer say cant be set textfield just like that
The context of where your TransactionViewController is, is not completely clear, but you are instantiating a new ViewController. If you want to refer to an existing ViewController, this is not the instance you are using here. If you want to create a new one and show it after your didSelectRowAtIndexPath, you have to make sure, that the TextField is instantiated in the init-Method of your ViewController. As you are not instantiating it from a Storyboard, it seems that your TransactionViewController is created programmatically. Probably you are setting the TextField only in viewDidLoad or something else after the init().
You are trying to set text to paymentTextField which is still no initialized.
For this you have to set text to paymentTextField in viewDidLoad method in TransactionViewController.
remove transVC.paymentTextField.text = title from didSelectRowAtIndexPath
Add it in TransactionViewController's viewDidLoad
override func viewDidLoad() {
super.viewDidLoad()
self.paymentTextField.text = self.payName
}
It is not correct way to do that. You have not initialised text field and trying to set it's text. First initialise text field:
transVC.paymentTextField = UITextField()
Then try to do something.