Swift Alert弹出窗口出现在模拟器iphone4s（8.1）中，而不是iphone4s（7.1）中

Question

I have written code to display a simple alert popup when a button is clicked. When trying the app in simulator iPhone 4s (8.1), it's working as expected, but when trying in simulator iPhone 4s (7.1), the app keeps crashing.

Here the code:

@IBAction func buttonPressed(sender: UIButton) {

    let controller = UIAlertController(title: "This is a title", message: "Hello, my friend", preferredStyle: UIAlertControllerStyle.Alert)
    let cancelAction = UIAlertAction(title: "Phew!", style: .Cancel, handler: nil)
    controller.addAction(cancelAction)
    self.presentViewController(controller, animated: true, completion: nil)
}

Here's the error message:

The first line code (the one creating the "controller" constant) is highlighted in green with the message "Thread 1: EXC_BAD_ACCESS(Code=1,address=0x10)"

I would appreciate any help

Answer 1

UIAlertController is available for iOS >= 8.0

You have to use UIAlertView for iOS < 8.0

Answer 2

UIAlertController is only available in iOS 8.0 and on wards unfortunately, here is documentation and it states this on the right: https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIAlertController_class/#//apple_ref/doc/uid/TP40014538-CH1-SW2

I believe this replaced the now deprecated UIAlertView which can be found here in Apple Documentation: https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIAlertView_Class/index.html#//apple_ref/occ/cl/UIAlertView

Swift doesn't like the old but consider and "if" clause and create both a UIAlertView and UIAlertController for the respective iOS system using the app.

Answer 3

Thanks to recommended links from Dom Bryan, I managed the following solution:

@IBAction func buttonPressed(sender: UIButton) {

    if NSClassFromString("UIAlertController") == nil{
        let alert = UIAlertView(title: "This is a title", message: "I am an iOS7 alert", delegate: self, cancelButtonTitle: "Phew!")
        alert.show()
    }else{
        let controller = UIAlertController(title: "This is a title", message: "Hello, my friend", preferredStyle: .Alert)
        let cancelAction = UIAlertAction(title: "Phew!", style: .Cancel, handler: nil)
        controller.addAction(cancelAction)
        self.presentViewController(controller, animated: true, completion: nil)
    }
}

And it's working fine on iOS7 and iOS8 devices