I'm a beginner trying to learn iOS.
I'm trying to show a sheet, but I'm finding it's not really showing anything.
This is what it looks like:
This is my relevant code:
class ViewController: UIViewController {
#IBAction func openMemoryLog(_ sender: UIButton) {
let memoryLogViewController = MemoryLogViewController()
present(memoryLogViewController, animated: true)
}
}
class MemoryLogViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
print("Memory log loaded")
if let presentationController = presentationController as? UISheetPresentationController {
presentationController.detents = [ .medium() ]
}
}
}
I can see the print statement going through, so it's at least loading. But don't know what's going on here. Looks like some sort of modal thing is happening, but the IB interface isn't showing.
When you use Storyboard / IB to design an interface, you have to instantiate that controller from the Storyboard - you cannot simply assign the class to a variable.
#IBAction func openMemoryLog(_ sender: UIButton) {
// if you designed MemoryLogViewController in Storyboard,
// you cannot create it like this:
//let memoryLogViewController = MemoryLogViewController() <-- wrong
// you need to instantiate it from the Storyboard
// for example, if you gave your controller a Storyboard ID of "memoryLogViewController":
if let memoryLogViewController = storyboard?.instantiateViewController(withIdentifier: "memoryLogViewController") {
present(memoryLogViewController, animated: true)
}
}
Related
I know this is a pretty common question but I've tried the various solutions offered here (that are not too old) and in numerous tutorials and I just can't seem to find out why it's still failing for me. Basically setting sendingViewController.delegate to self ends up being nil in sendingViewController. I understand this is very likely because the reference to the sendingViewController is being disposed of. But here is why I'm asking this again.
First, almost every tutorial and every other StackOverflow post is wiring up the mainViewController and the sendingViewController differently. I'm trying to make this work through a Navigation Controller, what one would think is the most common pattern for this.
In the app I'm building (which is more complex than the sample I'm going to show), the mainViewController calls the Settings viewController through a right navbar button. Then the user can select items from a list, which opens a controller with a searchBar and a tableView of items to select from. I need that third view controller to return the selected item from the table view to the settings screen. I'm using storyboards as well. I'm fairly new to Swift and I'm not ready to do all this "programmatically". Any way in the sending view controller, my delegate which should have been set in the calling view controller is nil and I can't invoke the protocol function in the main view controller to pass the data back.
I did a tutorial directly (not using Nav controllers) and I got that to work, but the moment I deviate away, it starts failing. I then put together a streamlined project with two view controllers: ViewController and SendingViewController. ViewController was embedded in a navigation controller and a right bar button was added to go to the SendingViewController. The SendingViewController has a single UI Button that attempts to call the protocol function and dismiss the SendingViewController. I'm not using Seque's, just a simple buttons and protocol/delegate pattern as I can.
My question is what am I missing to actually set the SendingViewController.delegate correctly?
Here's some code:
//ViewController.swift
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var showDataLabel: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
#IBAction func fetchDataButton(_ sender: UIBarButtonItem) {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let controller = storyboard.instantiateViewController(withIdentifier: "SendingViewController") as! SendingViewController
controller.delegate = self
print("fetching data")
present(controller, animated: true, completion: nil)
}
}
extension ViewController: SendingViewControllerDelegate {
func sendData(value: String) {
print("got Data \(value)")
self.showDataLabel.text = value
}
}
and
// SendingViewController.swift
import UIKit
protocol SendingViewControllerDelegate {
func sendData(value: String)
}
class SendingViewController: UIViewController {
var delegate: SendingViewControllerDelegate?
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
#IBAction func sendDataButton(_ sender: UIButton) {
print("attempting to send data \(self)")
print("to \(self.delegate)")
self.delegate?.sendData(value: "Hello World")
self.navigationController?.popViewController(animated: true)
}
}
Here is a screenshot of the Storyboard:
The ChildViewController does have a storyboard id name of "ChildViewController". All buttons and labels have their appropriate IBOutlet and IBAction's set up.
Help!
i copy paste your code .. its working perfect .. i make just one change
instead of pop you need to use dismiss as you are presenting from your base viewController
#IBAction func sendDataButton(_ sender: UIButton) {
print("attempting to send data \(self)")
print("to \(self.delegate)")
self.delegate?.sendData(value: "Hello World")
self.dismiss(animated: true, completion: nil)
}
here is the project link we.tl/t-NUxm9D26XN
I managed to get this working. In the receiving/parent view controller that needs the data:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let controller = segue.destination as! sendingViewController
controller.cityDelegate = self
}
Then in the sending view controller in my tableView did select row function:
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath)
{
let city = filtered[indexPath.row]
searchBar.resignFirstResponder()
self.navigationController?.popViewController(animated: true)
self.cityDelegate?.addCity(city)
self.dismiss(animated: true, completion: nil)
}
I don't think I should be both popping the view controller and dismissing it, but it works. Also in the view controller I did this:
private var presentingController: UIViewController?
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
presentingController = presentingViewController
}
override func didMove(toParent parent: UIViewController?) {
super.didMove(toParent: parent)
if parent == nil {
}
}
I don't know if I really need this didMove() or not since it doesn't really do anything.
But some combination of all this got it working.
In my other app I'm not using a navigation bar controller and the standard delegate/protocol method works like a charm.
I've set up a simple Swift project to try and wrap my head around delegates & protocols. The goal is to pass data between two classes (SendingClass & ReceivingClass). Two buttons in the SendingClass are linked to the delegate which should trigger the Protocol conforming function in the ReceivingClass to execute. This doesn't work unfortunately, I suspect it has to do with where and how I am declaring the ReceivingClass as the delegate.
Appreciate your insights, i'm just starting out!
I've tried setting the delegate in various locations (presently within viewDidLoad, but cant get it to work).
let vc = SendingClass()
vc.statusDelegate = self
SendingClass.swift
import UIKit
protocol StatusDelegate {
func statusChanged(state: Bool, sender: String)
}
class SendingClass: UIViewController {
var statusDelegate : StatusDelegate?
#IBAction func button1Pressed(_ sender: UIButton) {
statusDelegate?.statusChanged(state: true, sender: "Button 1")
}
#IBAction func button2Pressed(_ sender: UIButton) {
statusDelegate?.statusChanged(state: false, sender: "Button 2")
}
}
ReceivingClass.swift
import Foundation
import UIKit
class ReceivingClass: UIViewController, StatusDelegate {
override func viewDidLoad() {
let vc = SendingClass()
vc.statusDelegate = self
}
func statusChanged(state: Bool, sender: String) {
print("Sender = \(sender) , State = \(state)")
}
}
Expected: the ReceivingClass protocol conforming function (func statusChanged) should execute each time the buttons are pressed within the SendingClass.
Actual: Nothing happens
I am using this..
// create extension in your receiving class
extension ReceivingClass: PopUpVCDelegate {
func statusChanged(state: Bool, sender: String) {
print("Sender = \(sender) , State = \(state)")
}
}
// on sending class, when you present your receiving class on any button click
eg.
let resultController = self.storyboard?.instantiateViewController(withIdentifier: "PopUpVCID") as? PopUpVC
resultController?.delegate = self
self.present(resultController!, animated: true, completion: nil)
//or if not have button add on viewdidload in receiving class
// here is full eg
How to get data from popup view controller to custom table view cell?
For protocol and delegate, you use it when u want to bring a value from 2nd VC (presented by 1st or pushed by 1st VC) to 1st VC, which is the original.
From your code, I dont see you presenting or pushing your 2nd VC. that's why it's not working. Hopefully I answered your doubt.
However if you still want to bring a value over from 1st VC to 2nd VC. In second VC, create a variable to receive it
var ReceivedData = String()
then from your first VC, when u are going to push it,
let vc = SendingClass()
vc.ReceivedData = "Whatever you want it to receive"
If you're using storyboard segues, maybe the view controller is instantiated from there so probably you have to use the prepareForSegue and get the destination view controller (which is already instantiated for you) in the ReceivingClass view controller:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
super.prepare(for: segue, sender: sender)
if let destination = segue.destination as? SendingClass {
destination.delegate = self
}
}
Also be careful with delegate patter: the delegate property should be declared as a weak property to avoid retain-cycle
weak var delegate: MyDelegate?
Trying to pass data from one view controller MainScreenVC to Another RatesVC with protocol and extension, but that's not working, app crashing everytime . I'm clearly see that problem with code on second VC(because print showing correct data after action on first VC) but not sure where is error.
StoryBoard and 1st VC Example
Second VC
1st View controller
import UIKit
protocol transferNameOfCurrency {
func currencySelected(nameOfCurrency: String)
}
class MainScreenVC: UIViewController {
var transferCurrencyDelegate: transferNameOfCurrency?
var nameOfTheCurrency: String?
#IBAction func updateRates(_ sender: Any) {
nameOfTheCurrency = "EUR"
transferCurrencyDelegate?.currencySelected(nameOfCurrency:
nameOfTheCurrency)
print(nameOfTheCurrency)
}
}
2nd ViewController
import UIKit
class RatesVC: UIViewController {
var currencySelected: String?
override func viewDidLoad() {
super.viewDidLoad()
if let push = self.storyboard?.instantiateViewController(withIdentifier: "MainScreenVC") as? MainScreenVC
{
push.transferCurrencyDelegate = self
}
// Do any additional setup after loading the view.
}
}
extension RatesVC: transferNameOfCurrency {
func currencySelected(nameOfCurrency: String) {
currencySelected = nameOfCurrency
print(currencySelected)
}
}
The most obvious problem lies here:
if let push = self.storyboard?.instantiateViewController(withIdentifier: "MainScreenVC") as? MainScreenVC {
push.transferCurrencyDelegate = self
}
You have to realize that instantiateViewController creates a new view controller - it's not the reference to the view controller presented at the screen. In that code you just created a completely new view controller and then set its delegate to self, but otherwise nothing else.
Without knowing the context it is really hard to suggest anything - prepare(for:) segue might be the place where you want to set the delegate. Anyway, the problem is that you have to obtain a reference to the controller that is presented on the screen, the one that is supposed to be reacting to those events.
Moreover, from the memory management aspect, you should really consider making the delegate property a weak one to prevent memory leaks.
EDIT
So after seeing the minimal working example you provided at link, I think I can provide the solution on how to get that string to the SecondVC.
Your first view controller with comments:
import UIKit
class ViewController: UIViewController {
var newLine: String = "EUR"
#IBAction func push(_ sender: Any) {
// here the secondVC does not exist yet, calling delegate.transferWord() here would have no sense
// performSegue will create that secondVC, but now it does not exist, nor it is set up as the delegate
self.performSegue(withIdentifier: "ViewController", sender: navigationController)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let secondVC = segue.destination as? SecondVC, segue.identifier == "ViewController" {
// at this moment secondVC did not load its view yet, trying to access it would cause crash
// because transferWord tries to set label.text directly, we need to make sure that label
// is already set (for experiment you can try comment out next line)
secondVC.loadViewIfNeeded()
// but here secondVC exist, so lets call transferWord on it
secondVC.transferWord(word: newLine)
}
}
}
No need for delegates here, because your ViewController is the one pushing the SecondVC to the Navigation controller - that means that you can access it directly in prepare(for:), as you can see above.
Now the SecondVC is super simple (I omitted unnecessary code):
import UIKit
class SecondVC: UIViewController {
#IBOutlet weak var label: UILabel!
func transferWord(word: String) {
label.text = word
}
}
Storyboards can stay as they are.
i have a ViewController which is already loaded from the beginning of the app Lunching i need when the user logout from his AccountViewController ,so the Logout Icon in Side menu got hidden.
So in the Homepage i made that Protocol :
protocol HomeViewControllerDelegate {
func Menucheck()
}
then assign the delegate in ViewDidload():
var delegate: HomeViewControllerDelegate?
override func viewDidLoad() {
super.viewDidLoad()
delegate?.Menucheck()
then in the Side MenuViewController i did like that:
in ViewDidLoad():
let secondVC = Storyborad.instantiateViewController(withIdentifier: "HomeViewController") as! HomeViewController
secondVC.delegate = self
then i have used the delegate function like that:
extension SideMenuViewController: HomeViewControllerDelegate {
func Menucheck() {
print("i can hear you :) ")
if(preferences.double(forKey: User_ID) == 0)
{
LogoutSideIcon.isHidden = true
}else {
LogoutSideIcon.isHidden = false
}
}
Now when i go to homeViewController i suppose to see ("i can hear you") at least ,but actually nothing happen,i have tried to add to (Viewdidload) instead ,and i have tried to add it to a button action but nothing is happen ...
I have the following class below. The idea is it will use a custom Progress Window View Controller to handle progress of various different events. The problem is since this is in a class and not a view controller it's self, I'm not sure how to make the progressWindow actually show up after I instantiate it from the storyboard?
How do I do this? Currently I get an error that the application tried to present model view controller on itself.
import Foundation
import UIKit
class StatusProgress{
static var cancelCode = {}
static var runCode = {}
static var theProgressWindowController = ProgressWindowViewController()
static var returningViewControllerIdentifier = ""
static let storyboard = UIStoryboard(name: "Main", bundle: nil)
static func run(){
// This will run in parralel but on main queue. Has to be on this Queue because it might involve UI
dispatch_async(dispatch_get_main_queue(), {
// Update the UI on the main thread.
StatusProgress.runCode()
});
}
static func cancel(){
dispatch_async(dispatch_get_main_queue(), {
StatusProgress.cancelCode()
dispatch_sync(dispatch_get_main_queue(),{
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier(returningViewControllerIdentifier)
vc.presentViewController(vc, animated: true, completion: nil)
})
});
}
static func show(){
dispatch_async(dispatch_get_main_queue(),{
theProgressWindowController = self.storyboard.instantiateViewControllerWithIdentifier("progressWindow") as! ProgressWindowViewController
theProgressWindowController.presentViewController(theProgressWindowController, animated: true, completion: nil) //use own instance to show it's self? (throws error! application tried to present modal view controller on itself. Presenting controller is <Inventory_Counter.ProgressWindowViewController: 0x1466ea390>.')
})
}
}
My problem is essentially I need a replacement for this line of code.
theProgressWindowController.presentViewController(theProgressWindowController, animated: true, completion: nil)
I forgot to mention here is the code that runs it inside another view controller.
SyncViewController.swift
import UIKit
class SyncViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func yesSyncButtonAction(sender: UIButton) {
StatusProgress.returningViewControllerIdentifier = "syncWindow"
StatusProgress.runCode = {
print("run code test")
}
StatusProgress.cancelCode = {
print("cancel code test")
}
StatusProgress.show()
}
#IBAction func noSyncActionButton(sender: UIButton) {
tabBarController?.selectedIndex = 1 //assume back to inventory section
}
/*
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
// Get the new view controller using segue.destinationViewController.
// Pass the selected object to the new view controller.
}
*/
}
The biggest problem is that your StatusProgress class is instantiating and showing a view controller. View controllers should instantiate and show other view controllers, model objects should not. So you need to move the logic for presenting the new view controller into you SyncViewController. Then use delegation to communicate to the SyncViewController that the syncing is done.
protocol StatusProgressDelegate {
func statusProgress(status: StatusProgress, shouldShow: Bool)
func statusProgress(status: StatusProgress, shouldCancel: Bool)
}
Your StatusProgress object would have a delegate that conforms to that protocol and call that delegate inside of its show and cancel methods. This means that you need to make the static functions instance methods, and write an initializer for the class so you can instantiate it.
If the view life cycle events are not much important for you, you may just add the view of your progress controller to view of your current controller. or it's even better if you supply the UIView parameter in your show() function.
static func show(attachToView: UIView ){
dispatch_async(dispatch_get_main_queue(),{
theProgressWindowController = self.storyboard.instantiateViewControllerWithIdentifier("progressWindow") as! ProgressWindowViewController
attachToView.addSubview(theProgressWindowController.view)
})
}
After all you'd better to remove your progress view from superview
static func cancel(){
dispatch_async(dispatch_get_main_queue(),{
theProgressWindowController = self.storyboard.instantiateViewControllerWithIdentifier("progressWindow") as! ProgressWindowViewController
theProgressWindowController.view.removeFromSuperview()
})
}