I had a situation where a subview contains a button to dismiss it. I present an alert to confirm the action. It sends a message to the delegate - which is the view controller containing the subview - to remove the subview
Originally I presented a UIAlertView from a UIView. Refactoring for UIAlertController, since the UIAlertController can't present itself like a UIAlertView can, I came up with the following (in Swift; easily translated to ObjC):
Add a protocol to the subview:
protocol MySubviewDelegate {
// called when user taps subview/delete button
// or, you could call it from a gesture handler, etc.
func displayAlert(alert : UIAlertController)
// called when user confirms delete from the alert controller
func shouldRemoveSubview(sender : AnyObject)
}
Add a delegate for the subview, and add a handler for the button/gesture tap:
class MySubview : UIView {
var subviewDelegate : MySubviewDelegate!
...
func handleTap(sender : AnyObject) {
// set up the alert controller here
var alert = UIAlertController(title: "Confirm Delete",
message: "This action is permanent. Do you wish to continue?",
preferredStyle: UIAlertControllerStyle.Alert)
// Cancel action
// nil handler means "no action if Cancel button selected"
alert.addAction(UIAlertAction(title: "Cancel",
style: UIAlertActionStyle.Cancel,
handler: nil))
// Confirm action
alert.addAction(UIAlertAction(title: "Confirm",
style: UIAlertActionStyle.Default,
handler: { (action : UIAlertAction!) -> Void in
// call delegate method to perform confirmed action, - i.e. remove
self.subviewDelegate.shouldRemoveSubview(self)
}))
// call delegate method to display alert controller
// send alert object to delegate
self.subviewDelegate.displayAlert(alert)
}
}
Set the calling UIViewController as the delegate of the subview, e.g., in its viewDidLoad() method, and include protocol methods:
class viewController : UIViewController, MySubviewDelegate {
override func viewDidLoad() {
super.viewDidLoad()
self.subviewDelegate = self
...
}
func displayAlert(alert : UIAlertController) {
presentViewController(alert, animated: true, completion: nil)
}
func shouldRemoveSubview(sender : AnyObject) {
// cast as UIView / MySubview subclass
var subview = sender as MySubview
// remove the subview / perform the desired action
subview.removeFromSuperview()
...
}
...
}
This avoids the need to find the topmost view controller, or pass references to view controllers to subviews (other than in an object/delegate relationship).
