I have written my Spotlight API code and it seems to be working okay. I can check it out in the spotlight but there's only one problem :
It won't take me to the desired view controller! How do I do that? I've added a
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "showIt" {
let ThatVC = segue.destinationViewController as! ItThat
}
}
but it still won't take me to the right spot. Where am I going wrong?
prepareForSegue is used to notify the view controller that a segue is about to be performed (what data to prepare, confirms destination, etc). prepareForSegue is only called when a segue has already been initiated. It does not however perform the segue itself.
If your segue is unconditional, just use a standard segue in Interface Builder (pull from the UIButton to your destination scene).
If your segue is conditional, pull from the UIButton's parent scene to the destination scene in Interface Builder. Once this is finished, you can create a new #IBAction and perform a segue manually.
#IBAction func fooAction() {
performSegueWithIdentifier("showIt", sender: self)
}
Just make sure "showIt" is the segue's identifier.
Related
I have some quite simple doubt regarding optional binding,global variable & wrapping and unwrapping . Since I am new to SWIFT, its very important to understand the tits & bits of their concepts.
1) In Swift if I declare a global variable, I have 2 options either to make it optional or non optional, so let I am having 2-4 or more optional variables . So is it advisable to optional bind all those variables in
viewDidLoad() method// so that I could use them without any problem of unwrapping and fatal error in my program.
2) Let me make myself more clear by the following example- I have 2 VC in my project VC1 & VC2 . VC2 has a text field in which user enters some value and displays it in a tabelview in VC1.
In Vc1
var namevc1 = NSMutableArray?//holds the input of textfield to be passed from VC2.
As you can see, my VC1 is the first view controller that loads when my project runs and I am using an optional variable to populate my tabke vuew that is
'arr'
So when the app runs for the first time its empty . So it might cause a fatal error while using its value in the code. So what is its solution whether to unbind it in the
viewDidLoad()
method or in all total declare an empty NSMutable array type in place of optional type .
Thanks in advance.
I'll start by repeating the my comment from above.
Possibly you've misunderstanding the concept of global variables in Swift.
If you have a global variable, you won't have to "pass" it between any views/methods/classes etc, because the variable is defined at global scope (accessible everywhere).
Generally global variables is not a good idea, and something that you want to avoid.
Regarding the matter of global variables and swift, you really should include singletons into the discussion. See e.g. the following existing SO thread(s):
Any reason not use use a singleton "variable" in Swift?
(How to create a global variable?)
(Declaring Global Variables in Swift)
Communication between TableViewController and ViewController by means of segues (prepare for & unwind segues)
(This answer ended up being very and probably a bit too thorough, as I didn't know in detail what your current tableview/viewcontroller program state looks like. Sorry for the lengthy answer and any inconvenience it might bring to readers of it).
Now, lets leave global variables and discuss one (among other) viable options for the communication between the two controllers in your example. From your question, I'll summarize your example as follows
VC1: storyboard entry point, a UITableViewController consisting of UITableViewCells, where, in these cells, you display some text, say, via instances of UILabel.
VC2: a UIViewController, accessible from the cells of VC1, containing an UITextField instance. When user enters text into this text field, your want the text to be displayed in the associated cell in VC2 (associated in the sense that it was the cell in VC1 that was used to access VC2).
We'll associate VC1 and VC2 with (cocoa touch) classes TableViewController (TableViewController.swift) and ViewController (ViewController.swift), respectively. The cells in the table view controller will be associated with (cocoa touch) class TableViewCell (TableViewCell.swift). Details for these classes follow below.
For this simple example, note that we will not embed VC1 into a navigation controller (which is otherwise appropriate for table view -> view navigation).
We'll start in the storyboard, adding objects (drag-and-drop from object library) for a Table View Controller and a View Controller. The table view container will also, automatically, contain, in its Table View, a TableViewCell. Continuing in the storyboard:
Add a UILabel object to the TableViewCell container in the Table View Controller (align it as you wish)
In the View Controller, add a Text Field object and a Button object (align them as you wish).
Set the entry point to the Table View Controller.
Thereafter Ctrl-drag a 'Show' segue from the TableViewCell to the View Controller.
Select the Show segue and, from the Attributes inspector, enter an identifier for it, say, ShowDetail.
Finally, with the TableViewCell selected, (as above; from the attribute inspector), enter an identifier for the cell. Here, we'll use simply use identifier TableViewCell.
We now leave the storyboard for now and implement three classes, associated with the Table View Controller, the View Controller and the formers' TableViewCell.
We start with the Table View Controller, and implement our UITableViewController sub-class. Note that here, instead of using an NSMutableArray to hold the texts of the UITextLabel in each cell, we'll simply use a String array.
// TableViewController.swift
Import UIKit
class TableViewController: UITableViewController {
// Properties
var userTextLabels = [String]()
var numberOfCells: Int?
override func viewDidLoad() {
super.viewDidLoad()
numberOfCells = loadSampleTextLabels() // Load sample labels.
}
func loadSampleTextLabels() -> Int {
userTextLabels += ["Label #1", "Label #2", "Label #3"]
return userTextLabels.count
}
// func numberOfSectionsInTableView(tableView: UITableView) ...
// func tableView(tableView: UITableView, numberOfRowsInSection section: Int) ...
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cellIdentifier = ("TableViewCell")
let cell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier, forIndexPath: indexPath) as! TableViewCell
// Text for current cell
let cellText = userTextLabels[indexPath.row]
cell.userSuppliedTextLabel.text = cellText
return cell
}
// ... communication?
}
Where the two commented out methods are standard methods used in any UITableViewController, for number of sections (e.g. return 1) and cells (e.g. return (numberOfCells ?? 0)) in the table, respectively. I'll leave fixing these to you.
Now, we associate the TableViewCell object(s) in the table view with instances of a subclass to UITableViewCell. Here, we'll use a very simple class for our cells; each cell just containing a single UILabel instance (created via storyboard Ctrl-drag as an #IBOutlet from the UILabel in the table view cells).
// TableViewCell.swift
import UIKit
class TableViewCell: UITableViewCell {
// Properties
#IBOutlet weak var userSuppliedTextLabel: UILabel!
// Ctrl-drag from UILabel (in TableViewCell) in storyboard
override func awakeFromNib() {
super.awakeFromNib()
}
override func setSelected(selected: Bool, animated: Bool) {
super.setSelected(selected, animated: animated)
}
}
Finally, for the view controller that is accessed from the table view cells: use a single #IBOutlet to the UITextField used for user text input, and handle events in this text field using the pre-existing UITextFieldDelegate. E.g.:
// ViewController.swift
import UIKit
class ViewController: UIViewController, UITextFieldDelegate {
// Properties
#IBOutlet weak var userSuppliedText: UITextField!
// Ctrl-drag from storyboard...
var cellText: String?
override func viewDidLoad() {
super.viewDidLoad()
userSuppliedText.text = cellText ?? "..."
// Handle the user input in the text field through delegate callbacks
userSuppliedText.delegate = self
}
// UITextFieldDelegate
func textFieldShouldReturn(textField: UITextField) -> Bool {
// User finished typing (hit return): hide the keyboard.
textField.resignFirstResponder()
return true
}
func textFieldDidEndEditing(textField: UITextField) {
cellText = textField.text
}
}
We've also declared a string property (cellText) here, that will as act as container for communication between VC1 and VC2.
We return to the storyboard and---from the Identity inspector---associate the three storyboard objects (Table View Controller, View Controller, TableViewCell) with their associated classes that we've just written above.
We're now almost at our goal; it only remains to specify how to communicate between the two controllers.
We'll begin with communication from VC1 to VC2. In your comment above, you were on the right track (for this specific solution, anyway) by looking at the prepareForSegue(...) method. In the class for the Table View Controller, we add the following method:
// ... add to TableViewController.swift
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
// Get the new view controller using segue.destinationViewController.
// Pass the selected object to the new view controller.
if segue.identifier == "ShowDetail" {
let viewController = segue.destinationViewController as! ViewController
if let selectedCell = sender as? TableViewCell {
let indexPath = tableView.indexPathForCell(selectedCell)!
let currentTextInCell = userTextLabels[indexPath.row]
viewController.cellText = currentTextInCell // <-- note this
}
}
}
Hence, for VC1->VC2 communication, we can (in this example) bring whatever existing text that is currently occupying the UILabel in the sender cell (as is specified by the String array userTextLabels). Look at the viewDidLoad(...) method in the ViewController.swift to see how this value is passed from VC1 and set as default text in the UITextField in VC2.
Now, for communication VC2->VC1, which was the specific communication direction you were asking about, add another method (programmatically), again to TableViewController.swift:
// ... add to TableViewController.swift
#IBAction func unwindToTableView(sender: UIStoryboardSegue) {
if let sourceViewController = sender.sourceViewController as? ViewController,
text = sourceViewController.cellText {
// ^ note 2nd clause of if let statement above
if let selectedIndexPath = tableView.indexPathForSelectedRow {
// Update cell text
userTextLabels[selectedIndexPath.row] = text
tableView.reloadRowsAtIndexPaths([selectedIndexPath], withRowAnimation: .None)
}
}
}
Here, we define an unwind action that, when triggered, retrieves the cellText property of the view controller that was the source of the segue, i.e., in our case, the instance of ViewController. But how do we trigger this action?
Return to the storyboard and the View Controller. Note the three little icons in the top of the View Controller object, more specifically, the right-most of these, named Exit. Ctrl-drag an action from your Button to the Exit icon, and select the unwindToTableView Action Segue. When you click your button the view controller, the view unwind (exit) and land at the unwindToTableView method in the TableViewController.
The resulting app should look something like this:
This was way longer than I had expected, but once you get started writing... Anyway, the method above uses, naturally, no global variables, but make use of references to future (prepareForSegue) or historic (unwindToTableView) views to get (generally from current or historic view) or set (generally in current of future view) values by using these references (to future/historic view).
Apple has their own very thorough tutorial on an example app in the tableviewcontroller/viewcontroller context that I would recommend going over. I found it very valuable myself when I started coding Swift.
Start Developing iOS Apps (Swift)
What I need was to detect which cell was selected on my tableView, and using the indexPath.row to get the index of my object array which is personList, and pass that data to another View Controller and print on the label.
However, I received an error fatal error: unexpectedly found nil while unwrapping an Optional value
Below are my codes.
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath){
selectedCell = indexPath.row
performSegueWithIdentifier("DetailScreen", sender: nil)
}
override func performSegueWithIdentifier(identifier: String, sender: AnyObject?) {
//detailedView.personName = personList[selectedCell].GetPersonName()
detailedView.LastNameLabel.text = personList[selectedCell].GetLastName()
}
The problem is that you initialize the detailedView in the wrong way. Do it like this:
// IMPORTANT: Override prepareForSegue for your purpose, not performSegueWithIdentifier
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "DetailScreen" {
// Do the initialization here. You don't need a global variable.
if let detailedView = segue.destinationViewController as? PersonDetailScreen {
//detailedView.personName = personList[selectedCell].GetPersonName()
detailedView.LastNameLabel.text = personList[selectedCell].GetLastName()
}
}
}
PS: You are overriding the wrong function.
EDIT
As mentioned in your comment didSelectRowAtIndexPath and prepareForSegue doesn't coexist because the method you used for creating the segue is wrong. And with that, your code is doing more wrong than doing the right thing. Right now you might have created the segue by control dragging starting from the UITableView prototype cell to the destination view controller. Now when you do this what happens is, you are telling that the segue must be performed on the clicking on that particular cell itself, which means you are setting its action right in the storyboard. So even if you don't implement didSelectRowAtIndexPath, your code will still navigate to the second ViewController when the cell is clicked. But your requirement is that you must do some custom operations when the cell is clicked and then navigate to the second viewcontroller. For doing that, delete the current segue and then create a new segue with the same identifier like the way you create a normal segue - by control dragging from the source ViewContoller(not the tableview cell prototype) to the destination view controller. Then replace the override func performSegueWithIdentifier(identifier: String, sender: AnyObject?) function with the function I have provided in my original answer and then your code will work smooth.
PS: Make sure your Identifier is named correctly.
'NSInvalidArgumentException', reason: 'Receiver (<PersonDisplay.FirstViewController: 0x7feabaec2870>) has no segue with identifier 'DetailScreen''
This happens since you haven't set the name for the segue correctly in the storyboard. So rectify that as well. Specify the identifier for the segue in the storyboard.
You should pass valuable to detailedView and assign to label in viewDidLoad:
detailedView.lastName = personList[selectedCell].GetLastName()
Go viewDidload of detailedView:
detailedView.LastNameLabel.text = detailedView.lastName
I'm trying to pass variables from a view controller to another one. First, there's a connection screen. When the infos are verified, then I pass the username and other data to the whole program (that has a tab bar controller).
Here is the code. I'm using Xcode 6.4. In the previous version, the page would open but the variables didn't pass. Now it just gives me the above error.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if (segue.identifier == "lienConnecte") {
let nav = segue.destinationViewController as! UITabBarController // this line was just an attempt to find a solution
let vueFil = segue.destinationViewController as! FirstViewController
vueFil.utilisateur = utilisateur
}
}
Of course I know that in the storyboard, the segue points to the tab bar controller (because I need it afterwards), but I want the values to be passed to the FirstControllerView
Found the solution, for those who will see this post:
let tabBarController = segue.destinationViewController as! UITabBarController
let vueFil = tabBarController.viewControllers![0] as! FirstViewController
You cannot turn one thing into another, like some sort of magician, by saying as. You have to get a reference to the actual thing you're after. If there's a FirstViewController that is one of the child view controllers of the UITabBarController, then first get a reference to the UITabBarController (which you already know how to do), and then obtain its viewControllers property — those are its children, and you can, from there, get the one you want by its index number.
Your tab view controller is a container view controller that owns child view controllers. Presumably, FirstViewController is one of these child view controllers. Therefore, your tab view controller and your FirstViewController are different instances. You can access a tab bar's children with the viewControllers property:
let firstVC = tabVC.viewControllers?.first
// firstVC should be your FirstViewController
(Xcode6-beta3, Swift, iOS8, iPad)
In an iPad split-view controller, how do I link the Master View Controller to the Detail View Controller?
In other words, when the user taps on an item on the left, how do I change the view on the right?
I know that in didSelectRowAtIndexPath, I need to call a method... but how do I call a method in the Detail View Controller from the Master View Controller?
Example
Imagine an app to display information on different types of cheeses. We begin by dragging a split-view controller onto the storyboard. A table of items in the master view on the left is set up to read as follows.
Swiss
Cheddar
Brie
On the right, there is simply a Web View inside of the detail view controller, named cheeseViewController. Therein, HTML documents about the selected cheese will be displayed.
An IBOutlet is wired from the web view into cheeseViewController, and a method named 'changeCheese' is set up in the Detail View Controller delegate to swap out the document.
How can I make a tap on "Cheddar" change the information in the detail view?
EDIT: Do I have to modify my AppDelegate.swift file? Using a Master-Detail template, I tried the following, with no luck:
func application(application: UIApplication!, didFinishLaunchingWithOptions launchOptions: NSDictionary!) -> Bool {
// Override point for customization after application launch.
let splitViewController = self.window!.rootViewController as UISplitViewController
let navigationController = splitViewController.viewControllers[splitViewController.viewControllers.count-1] as UINavigationController
splitViewController.delegate = navigationController.topViewController as Paragraph
return true
}
I hope I understood your problem correctly: You would like to show the detail information of a selected cheese in your Detailview.
When you create a new Master-Detail-View application in XCode 6 Beta 3, there will be a variable called "detailItem" in your DetailViewController.Swift file:
var detailItem: AnyObject? {
didSet{
self.configureView()
}
You set this detailItem in your MasterViewController.Swift file in the following function:
override func prepareForSegue(segue: UIStoryBoardSegue, sender: AnyObject?){
if segue.identifier == "yourSegueIdentifier" {
let indexPath = self.tableView.indexPathForSelectedRow()
let cheeese = yourCheeseArrayWithDetailInformation[indexPath.row]
(segue.destinationViewController as DetailViewController).detailItem = cheeese
}
}
(Assuming, that you have linked the views with a segue with the identifier: "yourSegueIdentifier" and an array of detailinfo called "yourCheeseArrayWithDetailInformation")
The above mentioned function "configureView" in the DetailView can now access your detailItem, which contains the contents of "cheeese"
I hope this helps you.
Why don't you just post a Notification from didSelectRowAtIndexPath in your Master and add an observer in your Detail View most likely inside your viewDidLoad. You also can handle the selector within the observer method with closure.
If you didn't create a master-detail app (so you have no detailItem), you might use this:
if let
mySplitViewController = splitViewController,
detailView = mySplitViewController.childViewControllers.last as? DetailViewController {
// do something with it
}
I am new to IOS developing and recently started in Xcode 4.5. I saw for every viewController that i could set some identity variables including the storyboard ID. What is this, and how can I use it?
I started searching on stackoverflow and couldn't find any explanation for it.
I assumed it's not just some stupid label that I can set to remember my controller right? What does it do?
The storyboard ID is a String field that you can use to create a new ViewController based on that storyboard ViewController. An example use would be from any ViewController:
//Maybe make a button that when clicked calls this method
- (IBAction)buttonPressed:(id)sender
{
MyCustomViewController *vc = [self.storyboard instantiateViewControllerWithIdentifier:#"MyViewController"];
[self presentViewController:vc animated:YES completion:nil];
}
This will create a MyCustomViewController based on the storyboard ViewController you named "MyViewController" and present it above your current View Controller
And if you are in your app delegate you could use
UIStoryboard *storyboard = [UIStoryboard storyboardWithName:#"MainStoryboard"
bundle: nil];
Edit: Swift
#IBAction func buttonPressed(sender: AnyObject) {
let vc = storyboard?.instantiateViewControllerWithIdentifier("MyViewController") as MyCustomViewController
presentViewController(vc, animated: true, completion: nil)
}
Edit for Swift >= 3:
#IBAction func buttonPressed(sender: Any) {
let vc = storyboard?.instantiateViewController(withIdentifier: "MyViewController") as! ViewController
present(vc, animated: true, completion: nil)
}
and
let storyboard = UIStoryboard(name: "MainStoryboard", bundle: nil)
To add to Eric's answer and update it for Xcode 8 and Swift 3:
A storyboard ID does exactly what the name implies: it identifies. Just that it identifies a view controller in a storyboard file. It is how the storyboard knows which view controller is which.
Now, don't be confused by the name. A storyboard ID doesn't identify a 'storyboard'. A storyboard, according to Apple's documentation, 'represents the view controllers for all or part of your app’s user interface.' So, when you have something like the picture below, you have a storyboard called Main.storyboard which has two view controllers, each of which could be given a storyboard ID (their ID in the storyboard).
You can use a view controller's storyboard ID to instantiate and return that view controller. You can then go ahead to manipulate and present it however you want. To use Eric's example, say you want to present a view controller with identifier 'MyViewController' when a button is pressed, you would do it this way:
#IBAction func buttonPressed(sender: Any) {
// Here is where we create an instance of our view controller. instantiateViewController(withIdentifier:) will create an instance of the view controller every time it is called. That means you could create another instance when another button is pressed, for example.
let vc = storyboard?.instantiateViewController(withIdentifier: "MyViewController") as! ViewController
present(vc, animated: true, completion: nil)
}
Please take note of changes in syntax.