I am beginner in swift and working on one project where I am using collectionView. From collectionView, I want to transfer some values to details view but I am getting the above mentioned error. Values are not nil but somehow, it is giving this error while performing segue. Anybody help me, I am badly stuck here.
//In my CollectionView Controller.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if(segue.identifier == "DetailsView")
{
if let vc:DetailsViewController = segue.destinationViewController as? DetailsViewController
{
vc.details.text = self.description
vc.line.text = self.subText
vc.startTime.text = self.formatted_time
}
}
}
//DetailsViewController
import UIKit
class DetailsViewController: UIViewController {
#IBOutlet var startTime: UILabel!
#IBOutlet var line: UILabel!
#IBOutlet var details: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}
This basically means your IBOutlets are not yet initialised.
You should set strings and then in the viewDidLoad set you labels.
So to sum up:
Add string properties in your DetailsViewController
Set these string properties in your preparForsegue function
in the viewDidLoad of your DetailsViewController, set your labels
Your code should look like something like this :
//In my CollectionView Controller.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if(segue.identifier == "DetailsView")
{
if let vc:DetailsViewController = segue.destinationViewController as? DetailsViewController
{
vc.detailsString = self.description
vc.lineString = self.subText
vc.startTimeString = self.formatted_time
}
}
}
//DetailsViewController
import UIKit
class DetailsViewController: UIViewController {
#IBOutlet var startTime: UILabel!
#IBOutlet var line: UILabel!
#IBOutlet var details: UILabel!
var startTimeString: String?
var lineString: String?
var detailsString: String?
override func viewDidLoad() {
super.viewDidLoad()
startTime.text = tmpStartTimeString
line.text = tmpLineString
details.text = tmpDetailsString
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}
Double check my code, I've wrote it very quickly ;)
The IBOutlets in a destination view controller aren't set until some time after prepareForSegue finishes
In DetailsViewController, add three instance variables:
var startTime: String?
var line: String?
var details: String?
Then in prepareForSegue, set those three values:
vc.details = self.description
vc.line = self.subText
vc.startTime = self.formatted_time
Then in viewDidLoad of DetailsViewController
detailsLabel.text = self.details
lineLabel.text = self.line
startTimeLabel.text = self.startTime
As the two answer above are point out when you create an instance of a UIViewController like for example in the prepareForSegue when you call segue.destinationViewController as? DetailsViewController this not mean that the #IBOutlet's are injected or initialized yet. The #IBOutlet's are initialized when the view is fully loaded, so you can do two of the following options:
Create variables in your UIViewController in which you can save the values after the init of the UIViewController in the prepareForSegue and then in the viewDidLoad() of the another UIViewController you set the values for the #IBOutlet's.
Another option is call the view (e.g let _ = vc.view) property when you create the instance of the UIViewController, in this way you can force the view to load load fully and you can set your #IBOutlet's from the prepareForSegue.
I hope this help you.
Related
The variable latitude in ViewController1 is visible. Why is the variable from another ViewController empty? Whenever I run the code the .text property of ActualCoordinatesText label is empty...
class ViewControllerGpsMaps: UIViewController {
#IBOutlet weak var ActualCoordinatesText: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func GetCoordinates(_ sender: Any) {
GetActualCoordinates()
}
public func GetActualCoordinates() {
let sb = storyboard?.instantiateViewController(withIdentifier: "ViewController1") as! ViewController
ActualCoordinatesText.text = sb.latitude
}
}
Thanks for the help!
You are recreating a new instance of ViewController1 that means that the data included is the initialized value...
If your ViewControllerGPSMaps is called by VieController1 you should use the prepare(for segue:, sender:) of the ViewController1 to "give" the data you want to transfer...
I have ViewController, which has a textfield and a button. The user enters his name into the textfield and hits the DONE button. When he hits the button, he is segued to GifteeDetails, which is a different view controller. There is a label in that viewController that is supposed to display his name. But, his name doesn't show up. I don't receive an error.
Here's ViewController:
#IBOutlet weak var textGifteeName: UITextField!
#IBAction func toDetails(_ sender: Any) {
performSegue(withIdentifier: "toDetails", sender: nil)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let destDetails: GifteeDetails = segue.destination as! GifteeDetails
destDetails.nametext = textGifteeName.text!
destDetails.agetext = "\(Int(age)! - 2000 + 17)"
destDetails.locationstext = labelGifteeLocationsPreview.text!
destDetails.intereststext = labelGifteeInterestsPreview.text!
}
Here's GifteeDetails:
var nametext = String()
var agetext = String()
var locationstext = String()
var intereststext = String()
#IBOutlet weak var labelGifteeName: UILabel!
#IBOutlet weak var labelGifteeAge: UILabel!
#IBOutlet weak var labelGifteeLocations: UILabel!
#IBOutlet weak var labelGifteeInterests: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
nametext = labelGifteeName.text!
agetext = labelGifteeAge.text!
locationstext = labelGifteeLocations.text!
intereststext = labelGifteeInterests.text!
}
Sorry about all the !. Swift gives me an error unless I have them.
You are updating the strings nametext and others, which are not connected to your labels.
You need to replace this piece of code:
destDetails.nametext = textGifteeName.text!
destDetails.agetext = "\(Int(age)! - 2000 + 17)"
destDetails.locationstext = labelGifteeLocationsPreview.text!
destDetails.intereststext = labelGifteeInterestsPreview.text!
With:
destDetails.labelGifteeName.text = textGifteeName.text!
destDetails.labelGifteeAge.text = "\(Int(age)! - 2000 + 17)"
destDetails.labelGifteeLocations.text = labelGifteeLocationsPreview.text!
destDetails. labelGifteeInterests.text = labelGifteeInterestsPreview.text!
nametext is a String object, and it is different from labelGifteeName.text which is the String of the label you want to update.
If you use segue then pls remove it, and then create action method of that button in the FirstviewController and use pushViewController to move on the SecondviewController.
Swift 3
Example:
#IBAction func toDetails(_ sender: Any)
{
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewController(withIdentifier: "SecondView") as! SecondView
UserDefaults.standard.set(self. textGifteeName.text, forKey: "savedStringKey")
UserDefaults.standard.synchronize()
self.navigationController?.pushViewController(vc,
animated: true)
}
In SecondView:
override func viewDidLoad() {
super.viewDidLoad()
self.labelGifteeName.text = UserDefaults.standard.string(forKey: "savedStringKey")!
}
Please Update your func viewDidLoad() method in GifteeDetailsVC with labelGifteeName.text! = nametext , labelGifteeAge.text!= agetext instead of your code because you have already assigned the value in to strings i.e, nametext and agetext in ViewController, you need to display string value in label
I have a view controller embedded in another VC.
I would like to get the value of a variable from the main VC inside the embedded one. Specifically, I would like to change the text of label2 based on the value of label1.
I tried with "prepareForSegue", but it seems it's not triggered for embedded view controllers. I tried to isolate the problem in a test project:
Code for main VC:
class MyViewController: UIViewController {
#IBOutlet weak var label1: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
label1.text = "Hello"
}
}
Code for embedded VC:
class EmbeddedVC: UIViewController {
#IBOutlet weak var label2: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
}
Thanks for your help :)
A way to achiŠµve this is to get the child view controller instance in the parent's viewDidLoad. It appears that the parent's viewDidLoad: gets called after the child's viewDidLoad:, which means the label is already created in the child's view.
override func viewDidLoad() {
super.viewDidLoad()
if let childVC = self.childViewControllers.first as? ChildVC {
childVC.someLabel.text = "I'm here. Aye-aye."
}
}
First of all you can't set directly EmbeddedVC's lable2.text In prepareForSegue
because call sequence following below
MainVC's prepareForSeque this time EmbeddedVC's label2 is nil
EmbeddedVC's viewDidLoad called then label2 loaded
MainVC's viewDidLoad called then label1 loaded
so if you assign MainVC's label1.text to EmbeddedVC's label2.text in prepareForSeque
both label1 and label2 are nil so did not work
There are two way to solve this question
First Solution
MainViewController has EmbeddedVC and when MainVC's viewDidLoad called, assign label1.text to embeddedVC.label2.text
class MyViewController: UIViewController {
#IBOutlet weak var label1: UILabel!
var embeddedVC: EmbeddedViewController? = nil
override func viewDidLoad() {
super.viewDidLoad()
label1.text = "Hello"
embeddedVC?.label2.text = label1.text
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let embeddedVC = segue.destination as? EmbeddedViewController {
self.embeddedVC = embeddedVC
}
}
}
class EmbeddedViewController: UIViewController {
#IBOutlet weak var label2: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
}
Second Solution, use protocol and get MainVC's label text when viewWillAppear or viewDidAppear (later viewDidLoad called)
protocol EmbeddedVCDelegate: class {
func labelText() -> String?
}
class MyViewController: UIViewController, EmbeddedVCDelegate {
#IBOutlet weak var label1: UILabel!
// MARK: EmbeddedVCDelegate
func labelText() -> String? {
return label1.text
}
override func viewDidLoad() {
super.viewDidLoad()
label1.text = "Hello"
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let embeddedVC = segue.destination as? EmbeddedViewController {
embeddedVC.delegate = self
}
}
}
class EmbeddedViewController: UIViewController {
#IBOutlet weak var label2: UILabel!
weak var delegate: EmbeddedVCDelegate? = nil
override func viewDidLoad() {
super.viewDidLoad()
}
override viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
label2.text = delegate?.labelText()
}
}
You should try to use prepareForSegue like this:
if segue.identifier == "identifier" {
guard let destinationViewController = segue.destination as? VC2 else { return }
destinationViewController.label2.text = mytext
}
Where the segue identifier you assign in storyboard
I have two view. On my first view i create some data and send to other view lets name view2. So my view1 has code:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "showUserDetail" {
(segue.destinationViewController as! UserDetailTableViewController).detailContact = detailCoversationContact
}
}
In my detailCoversationContact i have detail about this one user, this detail like number, nick etc. Now as i expect this data are put to variable detailContact in my view2
And this is my cod in view2 this code is work:
class UserDetailTableViewController: UITableViewController {
#IBOutlet weak var nickNameLabel: UILabel!
var nickMy: String = ""
var detailContact: AnyObject? {
didSet {
// Update the user interface for the detail item.
if let detail = self.detailContact {
self.nickMy = (detail.valueForKey("nickName") as? String)!
}
}
}
override func viewDidLoad() {
super.viewDidLoad()
nickNameLabel.text = nickMy
}
}
When i send data to detailContact' i check is didSet if yes i set my nickMy and this is work. But what is first ? setting my var or viewDidLoad?
this is my code and not working and can someone explain why ?
class UserDetailTableViewController: UITableViewController {
#IBOutlet weak var nickNameLabel: UILabel!
var detailContact: AnyObject? {
didSet {
// Update the user interface for the detail item.
if let detail = self.detailContact {
self.title = detail.valueForKey("nickName") as? String
self.nickNameLabel?.text = (detail.valueForKey("nickName") as? String)!
}
}
}
override func viewDidLoad() {
super.viewDidLoad()
}
}
Ok this is self.title and work i see the name of user but title is from tableView. But my nickNameLabel is not change ? why ?
At the time of prepareForSegue, the IBOutlets have not been set up yet. So, self.nickNameLabel is still nil, and optional chaining makes self.nickNameLabel?.text = ... safely do nothing.
Set the value in viewDidLoad() when the IBOutlets have been set up:
override func viewDidLoad() {
super.viewDidLoad()
self.nickNameLabel?.text = (detail.valueForKey("nickName") as? String)!
}
Alternatively, you can trigger didSet by setting the detailContact to itself in viewDidLoad(). You have to trick Swift in order to do this because it thinks assigning detailContact to itself does nothing:
override func viewDidLoad() {
super.viewDidLoad()
detailContact = (detailContact) // trigger didSet to set up the label
}
After I click on a button I go to a new view controller.
I made it possible to make points with var score = 0 in a IBOutlet and to show to points I use Score.text = "\(++score)".
How can I pass the score to the 'Game over' screen/view controller to a label called "resultScore"?
Add an attribute secondViewController in the destination view controller, and use prepareForSegue
Current View Controller
override func prepareForSegue(segue: UIStoryboardSegue!, sender: AnyObject!) {
if (segue.identifier == "segueTest") {
var svc = segue!.destinationViewController as secondViewController;
svc.toPass = textField.text
}
}
in secondViewController you can define one variable like String
var toPass:String!
In the secondViewController under the viewDidLoad function add this code
println(\(toPass))
One easy way to achieve that is you can use NSUserDefault for that.
first of all in your playScene when you are increasing your score you can store your score this way:
Score.text = "\(++score)"
NSUserDefaults.standardUserDefaults().setInteger(score, forKey: "userScore")
After that in your next view controller you can get score this way:
resultScore = NSUserDefaults.standardUserDefaults().integerForKey("userScore")
Remember that type of your resultScore should be Int.
FirstViewController
#IBOutlet weak var textField: UITextField!
...
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if let vc = segue.destinationViewController as? GameOverViewController {
vc.score = Int(textField?.text)
}
}
...
SecondViewController
var score: Int!
#IBOutlet weak var label: UILabel!
...
override func viewDidLoad() {
super.viewDidLoad()
label.text = String(score)
}
This method will call when button was pressed, and in this place you may set some properties for your second view controller