I have an AlertController with a text field and two button: CANCEL and SAVE. This is the code:
@IBAction func addTherapy(sender: AnyObject)
{
let addAlertView = UIAlertController(title: "New Prescription", message: "Insert a name for this prescription", preferredStyle: UIAlertControllerStyle.Alert)
addAlertView.addAction(UIAlertAction(title: "Cancel",
style: UIAlertActionStyle.Default,
handler: nil))
addAlertView.addAction(UIAlertAction(title: "Save",
style: UIAlertActionStyle.Default,
handler: nil))
addAlertView.addTextFieldWithConfigurationHandler({textField in textField.placeholder = "Title"})
self.presentViewController(addAlertView, animated: true, completion: nil)
}
What I want to do is implement a check on the textfield for disabling the SAVE button when the textfield is empty just like Pictures Application of iOS when you want create a NewAlbum. Please someone can explain me what to do?
A TextField is a type of control that shows an editable text interface. In SwiftUI, a TextField typically requires a placeholder text which acts similar to a hint, and a State variable that will accept the input from the user (which is usually a Text value).
There is a much simpler way without using notification center, in swift:
weak var actionToEnable : UIAlertAction?
func showAlert()
{
let titleStr = "title"
let messageStr = "message"
let alert = UIAlertController(title: titleStr, message: messageStr, preferredStyle: UIAlertControllerStyle.alert)
let placeholderStr = "placeholder"
alert.addTextField(configurationHandler: {(textField: UITextField) in
textField.placeholder = placeholderStr
textField.addTarget(self, action: #selector(self.textChanged(_:)), for: .editingChanged)
})
let cancel = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.cancel, handler: { (_) -> Void in
})
let action = UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler: { (_) -> Void in
let textfield = alert.textFields!.first!
//Do what you want with the textfield!
})
alert.addAction(cancel)
alert.addAction(action)
self.actionToEnable = action
action.isEnabled = false
self.present(alert, animated: true, completion: nil)
}
func textChanged(_ sender:UITextField) {
self.actionToEnable?.isEnabled = (sender.text! == "Validation")
}
I would first create the alertcontroller with the save action initially disabled. Then when adding the textfield inculde a Notification to observe its change in the handler and in that selector just toggle the save actions enabled property.
Here is what I am saying:
//hold this reference in your class
weak var AddAlertSaveAction: UIAlertAction?
@IBAction func addTherapy(sender : AnyObject) {
//set up the alertcontroller
let title = NSLocalizedString("New Prescription", comment: "")
let message = NSLocalizedString("Insert a name for this prescription.", comment: "")
let cancelButtonTitle = NSLocalizedString("Cancel", comment: "")
let otherButtonTitle = NSLocalizedString("Save", comment: "")
let alertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)
// Add the text field with handler
alertController.addTextFieldWithConfigurationHandler { textField in
//listen for changes
NSNotificationCenter.defaultCenter().addObserver(self, selector: "handleTextFieldTextDidChangeNotification:", name: UITextFieldTextDidChangeNotification, object: textField)
}
func removeTextFieldObserver() {
NSNotificationCenter.defaultCenter().removeObserver(self, name: UITextFieldTextDidChangeNotification, object: alertController.textFields[0])
}
// Create the actions.
let cancelAction = UIAlertAction(title: cancelButtonTitle, style: .Cancel) { action in
NSLog("Cancel Button Pressed")
removeTextFieldObserver()
}
let otherAction = UIAlertAction(title: otherButtonTitle, style: .Default) { action in
NSLog("Save Button Pressed")
removeTextFieldObserver()
}
// disable the 'save' button (otherAction) initially
otherAction.enabled = false
// save the other action to toggle the enabled/disabled state when the text changed.
AddAlertSaveAction = otherAction
// Add the actions.
alertController.addAction(cancelAction)
alertController.addAction(otherAction)
presentViewController(alertController, animated: true, completion: nil)
}
//handler
func handleTextFieldTextDidChangeNotification(notification: NSNotification) {
let textField = notification.object as UITextField
// Enforce a minimum length of >= 1 for secure text alerts.
AddAlertSaveAction!.enabled = textField.text.utf16count >= 1
}
I am doing this in another project - I got this pattern directly from apple examples. They have a very good example project outlining a few of these patterns in the UICatalog examples: https://developer.apple.com/library/content/samplecode/UICatalog/Introduction/Intro.html
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