Calling delegate method from Swift's Extension class

Question

All I am implementing a UIAlertView extension for callback implementation like UIAlertView+Block in Objective C but the delegate method is not calling from this class any help. Thanks in advance.

Answer 1

The callback from the alert view runs in a background thread and the code receiving it is probably running in the main thread, as per apple documentation:

From the Apple iOS Documentation on Notification Centers:

In a multithreaded application, notifications are always delivered in the thread in which the notification was posted, which may not be the same thread in which an observer registered itself.

You need to call the notification back in the main thread otherwise strange things can happen

dispatch_async(dispatch_get_main_queue(), {
    //Call your notification from here
    NSNotificationCenter.defaultCenter().postNotificationName(mySpecialNotificationKey, object: self)
})

Answer 2

This is the updated answer after solving the issue.

typealias SelectBlock = (buttonIndex : Int) -> Void
typealias CancelBlock = () -> Void
private var blockSelect : SelectBlock?
private var blockCancel : CancelBlock?
extension UIAlertView {

    //Initilization
    func initWithTitle(
        title : String ,
        message : String,
        onSelect : SelectBlock?,
        onCancel : CancelBlock?,
        otherButtonTitles : [String]){

            //Initialize
            self.title = title
            self.delegate = self
            self.message = message

            //Block
            if let onSelectObj = onSelect? {
                blockSelect = onSelectObj
            }
            if let onCancelObj = onCancel? {
                blockCancel = onCancelObj
            }

            //Other buttons
            for buttons in otherButtonTitles {
                self.addButtonWithTitle(buttons)
            }

            //Cancel index
           // println("buttons \(self.numberOfButtons)")
            self.cancelButtonIndex = 0
            self.show()
    }

    func alertView(alertView: UIAlertView, didDismissWithButtonIndex buttonIndex: Int) {
        println("Index \(buttonIndex)")
        if buttonIndex == alertView.cancelButtonIndex {
            blockCancel!()

           // println("Cancel")
        }else{
            blockSelect!(buttonIndex: buttonIndex)
            // println("Retry")
        }
    }
}