// undokumentierte Methoden nutzen
@interface UIAlertView (extended)
- (UITextField *) textFieldAtIndex: (int) index;
- (void) addTextFieldWithValue: (NSString *)value label:(NSString *)label;
@end

// alert view erstellen 
UIAlertView *myAlert = [[UIAlertView alloc]
                          initWithTitle: @"Überschrift"
                          message:@"Text"
                          delegate:self
                          cancelButtonTitle:@"Abbrechen"
                          otherButtonTitles:@"OK", nil];
 
// Texteingabefelder hinzufügen
[myAlert addTextFieldWithValue:@"" label:@"Hinweistext"];
[myAlert addTextFieldWithValue:@"vorbelegter Text" label:@""];
   
// Texteingabefelder konfigurieren
UITextField *textfield = [myAlert textFieldAtIndex:0];
textfield.clearButtonMode = UITextFieldViewModeWhileEditing;
textfield.keyboardType = UIKeyboardTypeAlphabet;
textfield.keyboardAppearance = UIKeyboardAppearanceAlert;
textfield.autocapitalizationType = UITextAutocapitalizationTypeWords;
textfield.autocorrectionType = UITextAutocorrectionTypeNo;
  
textfield = [myAlert textFieldAtIndex:1];
textfield.clearButtonMode = UITextFieldViewModeWhileEditing;
textfield.keyboardType = UIKeyboardTypeURL;
textfield.keyboardAppearance = UIKeyboardAppearanceAlert;
textfield.autocapitalizationType = UITextAutocapitalizationTypeNone;
textfield.autocorrectionType = UITextAutocorrectionTypeNo;

[myAlert show];