iOS: How to present UIAlertController in iCloud Singleton? (Swift) - ios

Question

I'm creating a Singleton to manage my iCloud setup and configuration.
As part of the iCloud Design Guide the document states:
https://developer.apple.com/library/ios/documentation/General/Conceptual/iCloudDesignGuide/Chapters/iCloudFundametals.html
Listing 1-4 Inviting the user to use iCloud
if (currentiCloudToken && firstLaunchWithiCloudAvailable) {
UIAlertView *alert = [[UIAlertView alloc]
initWithTitle: #"Choose Storage Option"
message: #"Should documents be stored in iCloud and
available on all your devices?"
delegate: self
cancelButtonTitle: #"Local Only"
otherButtonTitles: #"Use iCloud", nil];
[alert show];
}
I've converted this to a UIAlertController in Swift but how can I run self.presentViewController(alert, animated: true, completion: nil) from my singleton?
Obviously my singleton does not have a member named 'presentViewController'
Is there anyway to do this or do I need to setup a Post Notification, present the Alert somewhere else in my program and then save/retrieve the user's selection?

Answer 1

1) Add custom protocol delegate to your singleton, and this delegate will return UIViewController instance
protocol TestSingletonDelegate : NSObjectProtocol {
func responderViewControllerForTestSingleton(singleton: TestSingleton)->UIViewController
}
And in your class:
let delegate: TestSingletonDelegate
func presentAlertView() {
let alertView = UIAlertView();
if (self.delegate.respondsToSelector("responderViewControllerForTestSingleton:")) {
let viewController = self.delegate.responderViewControllerForTestSingleton(TestSingleton())
viewController.presentViewController(alertView, animated: YES, completion: nil)
}
}
2) Add instance var to your singleton class, and story UIViewController variable there

Answer 2

I had the same issue, I solved it in my case by simply returning the alertController to the singleton and then presenting it there.
In the AlertView Class I have the below code for a simple alert that can take the title and message as input and display's only one OK button to dismiss the alert:
func alert(#alertTitle: String, alertMessage: String) -> UIAlertController {
var alertController = UIAlertController(title: alertTitle, message: alertMessage, preferredStyle: .Alert)
var okButton = UIAlertAction(title: "OK", style: .Default, handler: nil)
alertController.addAction(okButton)
return alertController
}
Note that in the above method I am not presenting the alert controller to the view rather just returning it to whom ever is calling the method.
Then in the class where I called the method I am doing the below code:
** Just a note that the class where I am calling the alert is a ViewController in Objective-C. I'll provide swift code below as well**
// Creating an instance of the AlertView class and initializing it
AlertView *testAlert = [[AlertView alloc] init];
/* Creating a UIAlertController object and then calling the method I created in the AlertView class. This way the returned UIAlertController will be assigned to this UIAlertController
*/
UIAlertController *alertController = [testAlert alertWithAlertTitle:#"Genius!" alertMessage:#"Pure Genius"];
// Finally presenting the alert controller
[self presentViewController:alertController animated:true completion:nil];
NOTE: that I've found that you have to do this outside of ViewDidLoad. It doesn't work in ViewDidLoad and gives the below error:
Attempt to present <UIAlertController: 0x1555118f0> on <ViewController: 0x155509790> whose view is not in the window hierarchy!
Instead you can do this in viewDidAppear method.
Now Swift Version of ViewController:
// Created a function to show the alert
func showAlert() {
// Creating an instance of the AlertView class and initializing it
var testAlert : AlertView = AlertView()
/* Creating a UIAlertController object and then calling the method I created in the AlertView class. This way the returned UIAlertController will be assigned to this UIAlertController
*/
var alertController : UIAlertController = testAlert.alert(alertTitle: "Genius", alertMessage: "Pure Genius")
// Finally presenting the alert controller
self.presentViewController(alertController, animated: true, completion: nil)
}
One more thing if you are trying to show this alert in a Singleton outside of the ViewController then you can retrieve the top view controller as below and then present the alert controller to it:
Objective - C:
UIViewController *topViewController = [UIApplication sharedApplication].keyWindow.rootViewController;
[topViewController presentViewController:alertController animated:true completion:nil];
Swift:
if let topViewController = UIApplication.sharedApplication().keyWindow?.rootViewController? {
topViewController.presentViewController(alertController, animated: true, completion: nil)
}

Answer 3

class SharedDataSingleton {
init(){
//println("Hellow World")
}
var sample = "Hellow word"
func showAlertView(title alerTitle:String ,message alertMessage:String, preferredStyle style:UIAlertControllerStyle, okLabel: String, cancelLabel: String, targetViewController: UIViewController,okHandler: ((UIAlertAction!) -> Void)!, cancelHandler: ((UIAlertAction!) -> Void)!){
let alertController = UIAlertController(title: alerTitle, message: alertMessage, preferredStyle: style)
let okAction = UIAlertAction(title: okLabel, style: .Default, handler: okHandler)
let cancelAction = UIAlertAction(title: cancelLabel, style: .Default,handler: cancelHandler)
// Add Actions
alertController.addAction(okAction)
alertController.addAction(cancelAction)
// Present Alert Controller
targetViewController.presentViewController(alertController, animated: true, completion: nil)
}
}
let sharedDataSingletonInstance = SharedDataSingleton()
> Access the values like below
sharedDataSingletonInstance.showAlertView(title: "Sample",
message: "Sample",
preferredStyle: UIAlertControllerStyle.Alert,
okLabel: "Ok",
cancelLabel: "Cancel",
targetViewController: self,
okHandler: { (action) -> Void in
println("The user is not okay.")
},
cancelHandler: { (action) -> Void in
println("The user is not okay.")
})
}
> Global Variables can be also accessed anywhere in our project
sharedDataSingletonInstance.sample