How to implement a YesNo box as a ViewController method? - ios

Question

I would like to add a method to my ViewController that shows a message with text as an alert with a Yes and a No button. The result should be of type Bool (Yes/No).
What I have tried is the following:
func YesNoBox(msg: String) -> Bool
{
var retVal = false
let alert = UIAlertController(title: "", message: msg, preferredStyle: .alert)
let action_yes = UIAlertAction(title: "Yes", style: .default, handler:
{ _ in NSLog("The \"Yes\" alert occured."); retVal = true })
let action_no = UIAlertAction(title: "No", style: .cancel, handler:
{ _ in NSLog("The \"No\" alert occured."); retVal = false })
alert.addAction(action_yes)
alert.addAction(action_no)
self.present(alert, animated: true, completion: nil)
return retVal
}
However, the value of retVal is always false. If I was in C/C++, I guess I could resolve this issue with a pointer, but this is Swift (and I am pretty new to this).
Any idea anyone how I could get this working?
EDIT: The problem that I have is the following. On a ViewController I have a TextField. When I tap on the text field, the app should ask the user whether they want to paste the text from the clipboard. If yes, paste, otherwise give the TextField the focus (i.e. let the cursor blink in it). I tried to do this with 'textFieldShouldBeginEditing' and in this method I display the YesNoBox. The problem is that the TextField never gets the focus after the YesNoBox is closed. And when I use 'becomeFirstResponder()' after the Box call, the app freezes. I don't know what to do?

Answer 1

Use a completion
func yesNoBox(msg: String,completion:#escaping(Bool) -> ())
{
let alert = UIAlertController(title: "", message: msg, preferredStyle: .alert)
let action_yes = UIAlertAction(title: "Yes", style: .default, handler:
{ _ in
NSLog("The \"Yes\" alert occured.");
completion(true)
})
let action_no = UIAlertAction(title: "No", style: .cancel, handler:
{ _ in
NSLog("The \"No\" alert occured.");
completion(false)
})
alert.addAction(action_yes)
alert.addAction(action_no)
self.present(alert, animated: true, completion: nil)
}
call
yesNoBox(msg:"someMessage") { yes in
if yes {
// do yes action
}
else {
// do no action
}
}
2 Callbacks:
This function has 2 completions ( imagine we have a function that uploads an image and notifies the progress with a completion and another 1 to say done )
func uploadImage(data: Data,progress:#escaping(Float) -> (),completion:#escaping(Bool) -> ()) {
// implementation here
}
To call
self.uploadImage(someData) { progress in
print(progress)
}) { done in
print(done)
}

Answer 2

This can be achieved with completion handlers.
func showAlertWithOptions(title: String, message: String, completionHandler: #escaping (Bool) -> Void) {
let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
let action_yes = UIAlertAction(title: "Yes", style: .default, handler: { _ in
completionHandler(true)
})
let action_no = UIAlertAction(title: "No", style: .cancel, handler: { _ in
completionHandler(false)
})
alert.addAction(action_yes)
alert.addAction(action_no)
self.present(alert, animated: true, completion: nil)
}
Now call the function and add any other functions or actions that you want to perform depending on the action selected.
showAlertWithOptions(title: "Any title", message: "Any message") { success in
if success {
NSLog("The \"Yes\" alert occured.")
} else {
NSLog("The \"No\" alert occured.")
}
}