I want to write iOS application based on VIPER architecture, so my goal is to get segue from router. I call view.performSegue(withIdentifier: sender:) from router and as sender i put closure that returns me a segue.
I want to override method prepare(for: sender:) for all view controllers in UIKit.
Actually I understand, that I can inherit from all classes, that have that method, and override it, but I want to do it once, for example in protocol, and after use it everywhere.
Any suggestions?
func prepare(for segue: UIStoryboardSegue, sender: Any?){
if let closure = sender as? (UIStoryboardSegue) -> (){
closure(segue)
}
}
You can try to create a BasicViewController which implement your override prepare function and use this when create another viewControllers.
Related
Say I have two screens. Screen A has a picker and a button, which triggers a segue to screen B, which displays some content depending on the option selected by the picker.
How do I have the information as to what picker was selected in A, passed to B? So far, I have A doing:
#IBAction func pickThing(_ value: Int) {
self.thing = value;
}
Which seems to work; I believe that it is detecting the value and storing it. However, when I try adding #IBOutlet weak var thingLabel: WKInterfaceLabel! to match the label in B, I can only set the value of it when the app first loads.
If I put self.thingLabel.setText("test") in the awake() function, it sets the label to "test", so that works. But changing it to self.thingLabel.setText("thing \(self.thing)") doesn't work - it sets it to whatever self.thing is initialized as, but doesn't change it later. So awake() is not the right method to use. I've also tried putting it in willActivate and in pickThing, but neither of them did anything.
Is there some method that gets called when a screen is switched to? If not, how can I send data from one screen to the next?
For example on ViewController A use this function
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let vc = segue.destination as? ViewControllerB {
vc.thing = self.thing
}
}
Or you can use closures in same methods and callback change from B ViewController on A
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let vc = segue.destination as? ViewControllerB {
vc.clouser = { [weak self] thingB in
guard let `self` = self else { return }
self.thing = thingB
}
}
}
You need to make a variable in view controller B titled something like "parentVC," which would be of view controller A's class. In view controller A's class, you need to call prepare(for segue UIStoryboardSegue, sender: Any?). In this method, you can access the segue's destination property, which would be view controller B. From here you can set view controller B's "parentVC" property to "self," i.e. view controller A. Then in view controller B's class you can access properties of view controller A by using the "parentVC" variable. The code in view controller A's class would look something like this:
func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.destination is ViewControllerB {
let viewControllerB = segue.destination as? ViewControllerB
viewControllerB.parentVC! = self
}
}
So I experimented with these 2 different ways of declaring a ViewController variable and it seemed to offer me the same results. However, I do feel there must be a difference between setting the destinationVC variable because if not, won't people use the more straightforward way of just declaring a new object?
[using segue.destination as! ViewControllerName]
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "changeCityName" {
let destinationVC = segue.destination as! ChangeCityViewController
destinationVC.delegate = self
}
}
[using ViewControllerName()]
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "changeCityName" {
let destinationVC = ChangeCityViewController()
destinationVC.delegate = self
}
}
In the prepareForSegue method, these two methods of creating a new VC differs greatly.
If you use segue.destination, you refer to the specific VC that the segue is going to, i.e. the one in your storyboard that the segue is connected to. If you create a new VC, then the VC you created won't be the same one as the segue is going to. i.e. you are dealing with a separate VC. Setting the delegate of the newly created VC won't do anything to the VC that is actually being presented.
If you are talking about the difference between using a segue to present a VC and this:
let vc = SomeViewController()
self.present(vc, animated: true)
Then the difference is less. If you use segues, then the views in the view controller will be read from the storyboard (NIB) file. If you create the VC by calling the initializer, you will have to handle adding the views in your view controller class.
Result may be visually same but its not true.
If you don't put any code inside prepare(for segue) still you will get same result(visually)
prepare(for segue) is called when UIViewControllers are connected through storyboard.
Since UIViewControllers are already connected in storyboard, so the destination UIViewController is called on your desired event.
In your first case using (segue.destination as! ViewControllerName) which is correct way of using segue.
Before going further one more thing is to be discussed about and that is
Why we are required to write code inside prepare(for segue) if its already connect through storyboard
1.From one button action you can connect several segues depending on your requirements, but each time button is pressed same prepare(for segue) method will be called, so to differentiate which UIViewController is to be called we do something like this
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if(segue.identifier == "FirstViewControllerIdentifier")
{
}else if(segue.identifier == "SecondViewControllerIdentifier"){
}else if(segue.identifier == "ThirdViewControllerIdentifier"){
}else{
// and so no
}
}
Now here we get object of destination controller(UIViewController) already being prepared.So we are not required to make a new object of destination controller
2.We can pass data to destination controller and also we can set delegate
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if(segue.identifier == "FirstViewControllerIdentifier")
{
// here we get object of first view controller and set delegate
let firstVC = segue.destination as! FirstViewController
firstVC.delegate = self
}else if(segue.identifier == "SecondViewControllerIdentifier"){
// here we get object of second view controller and pass some data to it
let secondVC = segue.destination as! SecondViewController
secondVC.someData = someData
}else if(segue.identifier == "ThirdViewControllerIdentifier"){
}else{
// and so no
}
}
Now in your second case using ViewControllerName() (the wrong code)
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if(segue.identifier == "FirstViewControllerIdentifier")
{
// here we create object of first view controller.This object is different from the destination view controller
//you create an object and set a delegate but after that you are not using that object and that object is totallu useless.
let firstVC = FirstViewController()
firstVC.delegate = self
// above code does not affect any thing but the contoller which is to be presented is destination view controller which is connected through storyboard
}
}
Hope you understand how to use segue and let me know if there is any problem
I have a MainViewController, that has a container view inside it that embeds a UIPageViewController. MainViewController conforms the protocols UIPageViewControllerDelegate, UIPageViewControllerDataSource
and I want the embedded UIPageViewController to be delegated by the MainViewController.
Is that even possible?
Basically I am trying to have a similar attitude to having a collection view inside a view controller as an outlet from storyboard, and then to setup the delegates for it (collectionView.delegate = self, assuming self delegates it)
So this attitude with a UIPageViewController.
The obstacle I encounter is that there is no PageView as opposode to PageViewController (comparing to collection views, I have CollectionView as opposed to CollectionViewController.
Here are the steps you could use to produce this:
You can get a reference to your UIPageViewController by overriding func prepare(for segue: UIStoryboardSegue, sender: Any?) in MainViewController. This function is triggered when your embedded controller is made a child.
Given you gave your segue a name (let's use pageSegue for this example), you are able to do something like this in MainViewController:
func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "pageSegue", let controller = segue.destination as? UIPageViewController {
controller.delegate = self
controller.dataSource = self
}
}
You can add a reference to your page view controller to your main view controller in the following way:
var walkthroughPageViewController: WalkthroughPageVC? {
return self.children.first as? WalkthroughPageVC
}
from here, you can just set walkthroughPageViewController.delegate = self
This method only works of course if you have one embedded view controller.
If you have more than one, Thomas' method above is better for grabbing the specific view controller you want.
Lets say I have 2 ViewControllers, in my MainViewController I have a button which performs a segue to SecondViewController. When button tapped, I'm saving some initial data to coreData, so it takes some time.
Here is the thing that I want to do;
While passing between ViewControllers, I want to show ActivityIndicator, but its starts after SecondViewController is opened. Could you help me? I'm new to Swift.
Here is the code I used in my MainVC:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if (segue.identifier == "SecondViewController") {
SwiftSpinner.show("Loading") // Act. indicator found on github
willRunOnce() // Here Im saving data to CoreData
SwiftSpinner.hide()
}
}
Instead of adding code of ActivityIndicator in prepare(for:sender:) method you need to call it in the Button action and after that call performSegue(withIdentifier:sender:) method.
#IBAction func onBtnSkip(_ sender: UIButton) {
SwiftSpinner.show("Loading") // Act. indicator found on github
willRunOnce() // Here Im saving data to CoreData
SwiftSpinner.hide()
//Now performSegue
self.performSegue(withIdentifier: "identifier", sender: nil)
}
I just going crazy on Swift Popover “return” values. I am new to Objectiv-C as well as SWIFT but I try to focus on SWIFT.
I checked out tutorials around Google and StackOverflow about how to manage iOS popovers, learned a lot but the last peace I couldn’t make it. It is great so see how easy it is made using Swift and Xcode 6, love it, but I could not figure out how to get back the selected value from my popover to my calling view controller.
So here is my problem:
(SIDENOTE: I am using SWIFT and do all using storyboard)
I have created a master ViewController with a button to select currencies. This button opens a “select currency” popover (linked to the CurrencyTableViewController (CTV) by CTRL-Dragging it to the CTV-Controller.
So far so good. The thing is, I have no idea how to get back the selected table row (currency) from the CTV-Table ;-( So I need the selected currency (table row) in the calling ViewController.
This is an excerpt from my ViewController (which is calling the popover)
class ViewController: UIViewController, UIPopoverPresentationControllerDelegate
[...]
// This button is calling the popover
#IBAction func buttonCurrency(sender: AnyObject) {
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if let controller = segue.destinationViewController as? CurrencyTableViewController {
controller.popoverPresentationController?.delegate = self
return
}
}
[...]
Hopefully somebody can help me with that missing last mile how to get back the selected row value back to my ViewController.
Thanks in advance
Cheers
John
I made quick example, hope it helps:
// This is you popover's class
#objc protocol CurrencySelectedDelegate {
func currencySelected(currName: String)
}
class MyPopOverController: UIViewController {
weak var delegate: CurrencySelectedDelegate?
#IBAction func readyButtonPressed(sender: AnyObject) {
// Do what you want
delegate?.currencySelected("Euro/Dollar etc....")
// close popover
}
}
// ViewController
class ViewController: UIViewController, CurrencySelectedDelegate {
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "mySegue" { // your identifier here
let controller = segue.destinationViewController as! MyPopOverController
controller.delegate = self
}
}
}
And remember just declare that currencySelected function in your ViewController.