here is my protocol definition.
protocol ActivityIndicatorDelegate: class {
func showIndicator()
func hideIndicator()
func barcodeError()
func categoryError()
func descError()
func reasonError()
func costError()
}
Then in my Custom cell class I create weak reference and I call delegate function
class ProductTableViewCell: UITableViewCell {
weak var indicatorDelegate: ActivityIndicatorDelegate?
#IBAction func stockUpdate(_ sender: Any) {
indicatorDelegate?.categoryError()
}
}
Then in my UITableViewController class
class ProductTableViewController:
UITableViewController,ActivityIndicatorDelegate{
override func viewDidLoad() {
super.viewDidLoad()
let cellDelegate = ProductTableViewCell()
cellDelegate.indicatorDelegate = self
}
func categoryError() {
//self.showAlert(alertTitle: "Error!", alertMessage: "Category Should not be empty")
print("Error")
}
}
I have written all these in a single file. What I'm doing wrong here? Can some one help me to solve this. Thanks in advance.
You should not set the delegate in viewDidLoad. This will only set the delegate of the cell that you just created, instead of all the cells in the table view.
You should do this in celForRowAtIndexPath:
let cell = tableView.dequeue...
// configure the cell...
cell.indicatorDelegate = self
Related
I am a beginner in Swift, and I do not yet understand all the elements.
I am trying to execute a function present in a ViewController (ProjectTabBarController) from another ViewController (ProjectInfosViewController). I end up with an error when I execute the function from the second.
For the context, it is for a navigation button of 3 UIViewController belonging to a UITabBarViewController, itself embedded in a UINavigationController
Thank you in advance ! (Sorry for my bad English)
import UIKit
//MARK:-TAB CONTROLLER
class ProjectTabBarController: UITabBarController {
#IBOutlet weak var ui_saveButton: UIBarButtonItem!
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func saveAction(_ sender: Any) {
// code
disableSaveButton() // ALL IT'S FINE HERE
}
func enableSaveButton() {
ui_saveButton.title = "Save"
ui_saveButton.isEnabled = true
}
func disableSaveButton() {
ui_saveButton.title = "Saved"
ui_saveButton.isEnabled = false
} }
//MARK:-PROJECT INFORMATIONS
class ProjectInfosViewController: UIViewController, UITextFieldDelegate {
let superController = ProjectTabBarController()
override func viewDidLoad() {
super.viewDidLoad()
}
func textFieldDidChangeSelection(_ textField: UITextField) {
superController.enableSaveButton() // BUT HERE, DOESN'T
} }
//MARK:-PROJECT FIXTURES
class ProjectFixturesViewController: UIViewController, UITableViewDataSource {
}
//MARK:-PROJECT CONTACT
class ProjectContactViewController: UIViewController {
}
This
let superController = ProjectTabBarController()
is a new vc that's not presented , if the vc is inside the tabController then do
let res = self.tabBarController as! ProjectTabBarController
res.......// call what you need
This is the error Xcode outputs
Unexpectedly found nil while unwrapping an Optional value
I have a viewcontroller that has a tableview and a few buttons; the buttons allow me to insert or remove data. It seems that when I click on Add (which brings up a new viewcontroller via segue as a sheet) the app crashes with the error above. Clicking on remove doesn't have this affect. So it has to do with something regarding the new viewcontroller as a guess. The console doesn't go further into the error other than printing out (lldb)
Here's my code
override func viewDidLoad() {
super.viewDidLoad()
alarmTableView.dataSource = self //error occurs here
alarmTableView.delegate = self //if i remove the above line if will occur here too.
}
My Viewcontroller which the above viewDidLoad func is embedded lists the protocols I need
class ViewController: NSViewController, NSTableViewDelegate, NSTableViewDataSource {
#IBOutlet weak var addAlarm: NSButton!
#IBOutlet weak var resetDataButton: NSButton!
#IBOutlet var alarmArrayController: NSArrayController!
#IBOutlet weak var alarmTableView: NSTableView!
#IBOutlet weak var deleteAll: NSButton!
#objc let moc: NSManagedObjectContext
required init?(coder: NSCoder) {
self.moc = CoreDataHandler.getContext()
super.init(coder: coder)
}
override func prepare(for segue: NSStoryboardSegue, sender: Any?) {
let destinationController = segue.destinationController as! AddAlarmViewController
//pass data to next controller here
}
#IBAction func deleteAllAction(_ sender: Any) {
if (alarmTableView.selectedRow >= 0) {
if (CoreDataHandler.deleteAllObjectsInEntity(entityName: "Alarm")) {
//remove from nsarray controller
for object in alarmArrayController.arrangedObjects as! [Alarm] {
print(object)
alarmArrayController.removeObject(object)
}
alarmTableView.reloadData()
}
}
else {
printInfo(str: "There are no alarms to delete")
}
}
/* Response to the remove alarm button - It removes a selected alarm object from the table */
#IBAction func resetDataAction(_ sender: Any) {
if (alarmTableView.selectedRow >= 0) {
let selectedAlarm = self.alarmArrayController.selectedObjects.first as! Alarm
alarmArrayController.remove(atArrangedObjectIndex: alarmTableView.selectedRow)
CoreDataHandler.deleteObjectInEntity(entityName: "Alarm", obj: selectedAlarm)
alarmTableView.reloadData()
}
else {
//will need a warning or play a sound.
printInfo(str: "Please select an alarm")
}
}
override func viewDidLoad() {
super.viewDidLoad()
printInfo(str: "viewdidload")
print(alarmTableView)
if (alarmTableView != nil) {
printInfo(str: "AlarmTableView Is initialised")
alarmTableView.dataSource = self
alarmTableView.delegate = self
}
else {
printInfo(str: "AlarmTableView is not initialised")
}
}
override var representedObject: Any? {
didSet {
// Update the view, if already loaded.
}
}
func printInfo(str: String) {
print("ViewController: \(str)")
}
func tableView(_ tableView: NSTableView, heightOfRow row: Int) -> CGFloat {
return 100.0
}
}
class AddAlarmViewController: ViewController {
#IBOutlet weak var closeButton: NSButton!
override func viewDidLoad() {
super.viewDidLoad()
// Do view setup here.
printClassInfo(str: "viewDidLoad")
CoreDataHandler.saveTestData()
}
#IBAction func closeButtonAction(_ sender: Any) {
self.dismissViewController(self)
}
func printClassInfo(str: String) {
print("AddAlarmViewController \(str)")
}
}
If I remove the lines where the error occurs the app run fine. But I want to override the delegate and datasource and use the functions to further customise the table. I'm also using Cocoa Bindings.
Why am I getting this error?
Update
I haven't solved it yet, but i placed a couple of print statements in my viewDidLoad function. It seems that when the app is first loaded, the table view is initialised. But after when I clicked on the Add button, the table view is then set to nil for some odd reason, as if another table view has been initialised. However the data is still visible
Problem:
class AddAlarmViewController: ViewController {
//...
override func viewDidLoad() {
super.viewDidLoad()
//...
}
}
Your AddAlarmViewController is a subclass of ViewController instead of NSViewController.
In AddAlarmViewController's viewDidLoad you call super.viewDidLoad() which basically calls ViewController's viewDidLoad.
But... in this case ViewController is a new instance as the super class of AddAlarmViewController and none of it's properties are initialized.
Whatever it be, it's probably not what you want.
Solution:
class AddAlarmViewController: NSViewController {
//... rest as it is
}
I have subclassed UITableViewCell. Here I have made an outlet for a button. When that button have been clicked on, it should execute a function in a different ViewController. I have tried this:
override func awakeFromNib() {
super.awakeFromNib()
reloadTableView.addTarget(self, action: #selector(multiplayerChannelView.tappedOnReloadTableView), for: .touchUpInside)
}
However, this crashes with this error:
[test.CreateChannelCell tappedOnReloadTableView]: unrecognized selector sent to instance 0x7fc1198b5200
The function exists, with no typo. Why does this not work? This question looks the same only it is not written in swift 3.0 How to set Action for UIButton in UITableViewCell
multiplayerChannelView is the viewcontroller which holds the UITableView. I got a seperated .swift file with the UITableViewCell subclassed.
add this in the cellForRowAtIndexPath
cell.your_button.addTarget(self, action: #selector(self.tappedButton(sender:)), for: .touchUpInside);
And anywhere in the same UIVeiwController define the function as below
func tappedButton(sender : UIButton){
// Your code here
}
You can do it by creating delegate in your tableViewCell class.
protocol CustomTableViewCellDelegate {
func buttonPressed ()
}
then initialize your delegate like below in your tableViewCell
var delegate: CustomTableViewCellDelegate?
and for button action put below code in your tableViewCell class
#IBAction func cellButtonPressed (sender : UIButton) {
if (self.delegate != nil) {
self.delegate?.buttonPressed()
}
On button click check wether delegate is not nil , please set cell.delegate = self in cellForRowAtIndex method
In the last just add code for button action in your classes where you have used customTableViewCell class
extension ViewController : CustomTableViewCellDelegate {
func buttonPressed () {
// Perfom your code on button action
}
}
your CustomTableViewCellDelegate looks like below:
import UIKit
protocol CustomTableViewCellDelegate {
func buttonPressed ()
}
class CustomTableViewCell: UITableViewCell {
var delegate: CustomTableViewCellDelegate?
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
}
#IBAction func cellButtonPressed (sender : UIButton) {
if (self.delegate != nil) {
self.delegate?.buttonPressed()
}
}
Hope it work for you!
write below code in file VC2
import UIKit
class tblCell : UITableViewCell
{
#IBOutlet weak var btnAction: UIButton!
#IBAction func btnAction(_ sender: AnyObject)
{
print(sender.tag) // you can identify your cell from sender.tag value
// notification is fire here and call notification from VC1
NotificationCenter.default.post(name:NSNotification.Name(rawValue: "buttonAction"), object: nil)
}
}
class VC2: UIViewController,UITableViewDelegate,UITableViewDataSource
{
#IBOutlet weak var tblview: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
tblview.delegate = self
tblview.dataSource = self
// Do any additional setup after loading the view.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Table veiw
func tableView(_ tblBlog: UITableView, numberOfRowsInSection section: Int) -> Int {
return 10
}
func tableView(_ tblBlog: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
{
let cell : tblCell = tblview.dequeueReusableCell(withIdentifier: "Cell") as! tblCell
cell.btnAction.tag = indexPath.row
return cell
//
}
}
write below code in file VC1
class VC1: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func viewWillAppear(_ animated: Bool)
{
// this notification is call when it fire from VC2
NotificationCenter.default.addObserver(self, selector: #selector(ButtonClick), name: NSNotification.Name(rawValue: "buttonAction"), object: nil)
}
func ButtonClick()
{
// code when button is clicked you wanto perfrom
}
}
in my view controller, i have set up like this.
protocol MenuDelegate {
func updateIndexOfMenuExpanded(index: Bool)
}
class ViewController: UIViewController,UITableViewDataSource, UITableViewDelegate {
var delegate : MenuDelegate?
func performaction() -> Void{
delegate!.updateIndexOfMenuExpanded(false)
}
}
and in my baseviewcontroller
class BaseViewController: UIViewController, MenuDelegate{
func updateIndexOfMenuExpanded(index: Bool){
self.menuIsExpanded = index
}
}
please help. thank you.
You have to set the delegate first.
let viewController = ViewController()
let baseViewController = BaseViewController()
viewController.delegate = baseViewController
It would also be wise to make the delegate a weak reference and to not force unwrap with !.
class ViewController: UIViewController,UITableViewDataSource, UITableViewDelegate {
weak var delegate : MenuDelegate?
func performaction() {
delegate?.updateIndexOfMenuExpanded(false)
}
}
Delegate is used when you want to pass data between viewcontrollers.this aproach is one to one
Here is the answer how to pass data using delegate
in viewcontroller
define protocol in view controller
protocol ViewController1BackClicked {
func btnBackClicked(str : String)
}
class ViewController1: UIViewController {
var strTitle : String?
var delegate : ViewController1BackClicked?
override func viewDidLoad() {
super.viewDidLoad()
if strTitle != nil{
title = strTitle
}
}
override func viewWillDisappear(animated: Bool) {
delegate?.btnBackClicked("Krutarth")
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
now Protocol is created.to pass data in another view controller
viewcontroller 1 we want to access data
func btnBackClicked(str: String) {
title = str
}
output : Krutarth
this is example how to use protocol
I'm fairly new at iOS programming. I have this setup:
ViewController view on IB, with class ViewController
SecondController view on IB, with class secondController
I have protocol:
protocol SecondControllerDelegate {
func getSomething() -> String
}
and I have delegate variable on SecondController:
class secondController: UIViewController {
var delegate: SecondControllerDelegate?
#IBOutlet weak var labelStatus: UILabel!
override func ViewDidLoad() {
super.viewDidLoad()
}
#IBAction func buttonTouch(sender: AnyObject) {
labelStatus.text = delegate?.getSomething()
}
func try () {
labelStatus.text = "testing"
}
}
Now, according to the hints everywhere, in order so I can call delegate?.getSomething() at SecondController.buttonTouch(), I need to set like this on viewController:
class ViewController: UIViewController, SecondControllerDelegate {
override func viewDidLoad () {
super.viewDidLoad()
SecondController.delegate = self
}
func doSomething () -> String {
return "testing"
}
}
But this generates error 'SecondController.type' does not have a member named 'delegate'.
Some other websites say:
class ViewController: UIViewController, SecondControllerDelegate {
var secondController = SecondController()
override func viewDidLoad () {
super.viewDidLoad()
secondController.delegate = self
}
func doSomething () -> String {
return "testing"
}
}
With this, there are no error. But if I do something on the second screen that should call the delegate, it doesn't call the delegate, like the SecondController is two different objects (one is created by StoryBoard, one is created manually within the ViewController), i.e. the labelStatus that should have changed to "testing", doesn't change at all. But it changes if function try() is called. How am I supposed to do this?
EDIT: I forgot to mention that I used NavigationController, and segue to transition from first screen to second screen.
Because you try to learn how to build a delegate in Swift, I have written you a plain delegate example below
protocol SecondViewControllerDelegate {
func didReceiveInformationFromSecondViewcontroller (information: String)
}
class ViewController: UIViewController, SecondViewControllerDelegate {
func openSecondViewController () {
if let secondViewControllerInstance: SecondViewController = storyboard?.instantiateViewControllerWithIdentifier("SecondViewController") as? SecondViewController {
secondViewControllerInstance.delegate = self
navigationController?.pushViewController(secondViewControllerInstance, animated: true)
}
}
func didReceiveInformationFromSecondViewcontroller(information: String) {
////Here you get the information, after sendInfoToViewController() has been executed
}
}
class SecondViewController: UIViewController {
var delegate: SecondViewControllerDelegate?
func sendInfoToViewController () {
delegate?.didReceiveInformationFromSecondViewcontroller("This ist the information")
}
}
UPDATE
Following the same thing in using Storyboard Segues
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if let secondViewControllerInstance: SecondViewController = segue.destinationViewController as? SecondViewController {
secondViewControllerInstance.delegate = self
}
}