Auf diese Weise können Sie das Problem in einem SSN-Überprüfungsfeld behandeln. Sie können die maximale Länge ändern und ifbei Bedarf die Anweisungsprüfung für den Tastaturtyp entfernen .
Es gibt auch eine Logik zum Unterdrücken der Warnungen für die maximale Länge, wenn der Benutzer tippt, anstatt Daten einzufügen.
Im Kontext dieses Codes gibt presentAlert()/presentAlert:es nur einige grundlegende Funktionen, die eine UIAlertController(oder eine Legacy- UIAlertView) Funktion unter Verwendung der übergebenen Nachrichtenzeichenfolge darstellen.
Swift 5
// NOTE: This code assumes you have set the UITextField(s)'s delegate property to the
// object that will contain this code, because otherwise it would never be called.
//
// There are also some better stylistic approaches in Swift to avoid all the
// nested statements, but I wanted to keep the styles similar to allow others
// to contrast and compare between the two languages a little easier.
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
// Handle backspace/delete
guard !string.isEmpty else {
// Backspace detected, allow text change, no need to process the text any further
return true
}
// Input Validation
// Prevent invalid character input, if keyboard is numberpad
if textField.keyboardType == .numberPad {
// Check for invalid input characters
if CharacterSet(charactersIn: "0123456789").isSuperset(of: CharacterSet(charactersIn: string)) {
// Present alert so the user knows what went wrong
presentAlert("This field accepts only numeric entries.")
// Invalid characters detected, disallow text change
return false
}
}
// Length Processing
// Need to convert the NSRange to a Swift-appropriate type
if let text = textField.text, let range = Range(range, in: text) {
let proposedText = text.replacingCharacters(in: range, with: string)
// Check proposed text length does not exceed max character count
guard proposedText.count <= maxCharacters else {
// Present alert if pasting text
// easy: pasted data has a length greater than 1; who copy/pastes one character?
if string.count > 1 {
// Pasting text, present alert so the user knows what went wrong
presentAlert("Paste failed: Maximum character count exceeded.")
}
// Character count exceeded, disallow text change
return false
}
// Only enable the OK/submit button if they have entered all numbers for the last four
// of their SSN (prevents early submissions/trips to authentication server, etc)
answerButton.isEnabled = (proposedText.count == 4)
}
// Allow text change
return true
}
Ziel c
// NOTE: This code assumes you have set the UITextField(s)'s delegate property to the
// object that will contain this code, because otherwise it would never be called.
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
// Handle backspace/delete
if (!string.length)
{
// Backspace detected, allow text change, no need to process the text any further
return YES;
}
// Input Validation
// Prevent invalid character input, if keyboard is numberpad
if (textField.keyboardType == UIKeyboardTypeNumberPad)
{
if ([string rangeOfCharacterFromSet:[NSCharacterSet decimalDigitCharacterSet].invertedSet].location != NSNotFound)
{
[self presentAlert: @"This field accepts only numeric entries."];
return NO;
}
}
// Length Validation
NSString *proposedText = [textField.text stringByReplacingCharactersInRange:range withString:string];
// Check proposed text length does not exceed max character count
if (proposedText.length > maxCharacters)
{
// Present alert if pasting text
// easy: pasted data has a length greater than 1; who copy/pastes one character?
if (string.length > 1)
{
// Pasting text, present alert so the user knows what went wrong
[self presentAlert: @"Paste failed: Maximum character count exceeded."];
}
// Character count exceeded, disallow text change
return NO;
}
// Only enable the OK/submit button if they have entered all numbers for the last four
// of their SSN (prevents early submissions/trips to authentication server, etc)
self.answerButton.enabled = (proposedText.length == maxCharacters);
// Allow text change
return YES;
}