So I have multiple buttons on one view segue'ing to other views. I have the function prepareForSegue() at the bottom of my code preparing one segue, however the app crashes when I use another segue on the view, even if it doesn't need any preparing.I think that the problem is that all of the segues use the prepareForSegue() function, however the storyboard ID is different than the view it is transitioning to.Is there any way to specify a prepareForSegue() function for each separate segue on the same view?Code:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let theVC: ViewController = segue.destinationViewController as! ViewController
theVC.receivedString = "true"
}
Thanks
In your prepareForSegue you should use a condition to check segue identifier like:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if(segue.identifier == "yourSegueToAnyController")
{
//do code for specific viewController
}
}
Related
I have a container view in my Storyboard that displays another view controller that I already programmed and stuff. I want to communicate between the main View Controller and the contained-view controller. I know how to use delegates and I am comfortable with using them, however I normally set up delegates when I initialize a ViewController, however in this case I don't know where to apply this, since the view controller is already there per the storyboard. Normally I would do something like this:
class HomeVC: UIViewController {
func initializeVC() {
resultsVC = self.storyboard?.instantiateViewController(withIdentifier: "resultsView") as! GoalsVC
resultsVC.calcDelegate = self //I set the "HomeVC" as the Delegate since it has all the functions I need
}
}
As mentioned above, since I never really created this view controller via code, I don't know how to assign a delegate (specially setting the delegate to "self" (where Self is the main View Controller)
You can assign delegate in prepareforsegue. Like below code
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if (segue.identifier == "container_segue") {
let controller = segue.destination as! containerController
controller.delegate = self
}
}
When project runs, this method called automatically because we had created segue in the storyboard.
By using segue.identifier you can check for which controller segue is going to happen and accordingly you can achieve your requirement.
As you are using storyboard for container view. There is a segue with embed type. Give this segue a identifier, say MyContainedViewControllerSegueId
Then in prepare(for segue:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "MyContainedViewControllerSegueId" {
// here you get your contained view controller as `segue.destination`
// cast it your subclassed view controller
// use delegate on that subclassed view controller for communication purpose.
}
}
I have 2 buttons in a view controller. If button 1 is clicked, then go to WebView controller. If button 2 is clicked then go to ArtView controller.
How to make override func prepare(for segue: UIStoryboardSegue, sender: Any?) have 2 destinations depending on the button clicked?
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destination = segue.destination as? WebViewController {
// your code
}
if let destination = segue.destination as? ArtViewController {
// your code
}
}
Hope it will help! :)
Have each button invoke a different segue, either by control-dragging segues directly from the button, or by calling performSegue(withIdentifier:sender:) from your buttons' IBAction code.
Then use code in prepare(for:sender:) to figure out which destination is being invoked.
You can:
Check the identifier on the segue (not recommended - fragile)
Check the class of the destination view controller (better than 1)
Have each view controller implement a protocol and check the protocol of the destination:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
switch segue.destination {
case let webView as WebViewProtocol:
//Your code for a web view
case let artView as ArtViewProtocol:
//Your code for an Art View
}
}
Option 3 is reliable while providing loose coupling (each case can trigger any view controller that conforms to the desired protocol. All it needs to know is that the destination understands the desired protocol.)
I am wondering about how the functions in the title work and also about the sender parameter.
Lets say a button click calls the performSegue method, does that also call the prepareSegue method as well? Is the prepareSegue method called before the performSegue method but after the button is pressed?
Also, is the "sender" parameter in both of the functions linked? If I pass in a string as the sender in the performSegue method, will that transfer over to the sender parameter in the prepareSegue method? In other words, if I set the sender parameter in the performSegue method as "Hi world", will the sender parameter in the prepareSegue method also be the same string?
Thanks
There are, effectively, two ways you can trigger a segue. The first is via an action on a UI element in Interface Builder, the second is using performSegueWithIdentifier:sender: in your code. I say 'effectively', because under the covers, when the scene is loaded from the storyboard, an action handler is configured that ultimately calls performSegueWithIdentifier:sender:
When performSegueWithIdentifier:sender: is called, the segue object is delivered to your view controller's prepareForSegue:sender: function.
In the case where the segue was initiated by an action on a UI element then the sender will be that UI element (i.e. if it is an action connection on a UIButton then the sender will be the UIButton instance).
If the segue is initiated by your code calling performSegueWithIdentifier:sender: then the sender will be whatever object you passed as the sender. This could be your view controller, a button, an array, anything. So yes, if you pass "Hello World" to performSegueWithIdentifier:sender: as the sender value then this will be the sender in prepareForSegue:sender:
In terms of the order of operations:
performSegueWithIdentifier:sender is called, either by your code or as a result of an action on a UI element
If your view controller implements shouldPerformSegueWithIdentifier:sender: then this function is called. If this function returns false then the segue is cancelled
The segue object and destination view controller object are created
If your view controller implements prepareForSegue:sender: then this function is called.
Once prepareForSegue:sender: returns, the segue completes.
The performSegue method calls a segue to be performed from one view to another. Before the segue actually takes place, the prepareForSegue method is called, and if you want to pass data between the views, you'd do it there.
The performSegue method doesn't take the parameter you want to send. It's only used to call the segue in the first place. Any data that you want to send will be done through prepareForSegue.
Here's an example.
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
performSegueWithIdentifier("test", sender: self)
//You can set the identifier in the storyboard, by clicking on the segue
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "test"{
var vc = segue.destinationViewController as! RandomViewController
vc.data = "Data you want to pass"
//Data has to be a variable name in your RandomViewController
}
}
Let me know if this helps!
The_Curry_Man's answer worked for me. Here's an update of his code for Swift 3.
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
performSegue(withIdentifier: "test", sender: self)
//You can set the identifier in the storyboard, by clicking on the segue
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "test"{
var vc = segue.destinationViewController as! RandomViewController
vc.data = "Data you want to pass"
//Data has to be a variable name in your RandomViewController
}
}
my two cents for beginners... In swift 3 is:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
}
So, if arriving controller (of class MyController) implements a "fillData" method:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destController = segue.destination as MyController{
destController.fillData(...)
}
}
Updated Method for Swift 5
performSegue(withIdentifier: "showNextViewController", sender: self)
Note : "showNextViewController" is identifier added for segue in storyboard
while sending any object to the particular object to another view controller by using perform segue with an identifier, Please follow the steps #Swift4
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "Detailed_Live_poll"{
let destinationNavigationController = segue.destination as! UINavigationController
let targetController = destinationNavigationController.topViewController as! NewLivePollViewController
targetController.dictQuestInf = sender as! NSDictionary
}
}
In my iOS project I use two kinds of UIStoryboardSegue, which present a view either within a navigation controller or as a modal view. I set the kind property in Interface Builder to:
Show (e.g. Push)
Present Modally
Now I want to be able to programmatically identify the kind of segue in order to customise the appearance of my ViewController. Like so:
class ViewController : UIViewController {
var isModal : Bool = false
...
}
class OtherViewController : ViewController {
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.destinationViewController is ViewController {
let vc = segue.destinationViewController as! ViewController
vc.isModal = TODO
}
}
}
I was hoping there would be a property, but I can't find it. I was also hoping that the segue class would differ, but I also can't find enough documentation.
I originally stumbled upon this problem trying to use the isModal in order to alternate between dismissing the ViewController vs. popping the ViewController. I have noticed that there now seems to be a better alternative, which is the UnwindSegue. However, I still need the flag in order to customise appearance..
Thanks
Maybe I'm totally wrong but can't you use the identifier of the segue?
For example name all modal view controllers with Modal<Name>. Then check
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?)
{
if segue.identifier.hasPrefix("Modal") {
let vc = segue.destinationViewController as! ViewController
vc.isModal = TODO
}
}
I have a segue running form a Collection View (wrapped in a view controller) in to a another view controller, how ever the function never gets called:
func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
println(segue.identifier)
println(sender)
println("SEGUE SELECTED: \(segue.identifier)")
if(segue.identifier == "segueToDetailView") {
let cell = sender as CollectionViewCell;
}
}
Have placed a breakpoint at start of function but never reached.
Any input appreciated.
I will suggest not to create segue(s) from cell or any object(like button).
Create segue from one ViewController to OtherViewController with unique identifier.
And then call the performSegueWithIdentifier yourself using the identifier.