Remove/Update an element from NSMutableArray when User press backspace in UITextField - ios

Question

I am using one third-party library HashtagMentionController. Here is the method which I use
- (void) hashtagMentionController:(HashtagMentionController *)hashtagMentionController onMentionWithText:(NSString *)text range:(NSRange)range {
if ([text isEqualToString:#""]) {
if ([self.arrFinalUUID count] < 1) {
self.userListView.hidden = FALSE;
[self.txtNotes resignFirstResponder];
self.replaceRange = range;
self.matchedNames = [[self.names filteredArrayUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(id evaluatedObject, NSDictionary *bindings) {
return [evaluatedObject rangeOfString:text].location != NSNotFound;
}]]mutableCopy];
self.matchedNames = names;
[self.tableHashtag reloadData];
} else {
[self presentViewController:[Common alertWithTitle:NSLocalizedString(#"Alert", #"Message") withMessage:NSLocalizedString(#"You can not select more than 1 user", #"Message") preferredStyle:UIAlertControllerStyleAlert] animated:YES completion:NULL];
}
} else {
NSLog(#"backspace pressed");
}
}
I have added this method in my UITextView when user press #.
Now I want a user to add only one name is textfield. I show an alert when the user adds second but there is a problem in this method when I press backspace and remove all the text still there is a value in that array.
So I want to handle backspace in this method(When there is no user I want to allow the user to remove an old array and add new value)
I can update my question if anyone requires more info.
Thanks in advance.

Answer 1

Using this code you can able to detect backspace:
const char * _char = [string cStringUsingEncoding:NSUTF8StringEncoding];
int isBackSpace = strcmp(_char, "\b");
if ([self.arrFinalUUID count] < 1) {
if (isBackSpace == -8) {
NSLog(#"Backspace was pressed"); // So you can allow the user to remove an old array.
}
}
You just have to change you conditions with isBackSpace. Let me know if you required more information.
Hope this code will help you.

Answer 2

I didn't understood exactly what your requirement is but, so far I think you can use one of UITextField's delegate method textField:shouldChangeCharactersInRange:replacementString: By using this delegate method you can access every character you type live. Only single character in other words you can get which key is pressed on keyboard.
For more on this method go here for documentation.
For detecting spacebar and backspace keys I use the following code:
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
//Add this condition if you need to know about a specified text field.
if(textField==yourTextField)
{
NSLog(#"Tapped key is:%#",string);
if([string isEqualToString:#" "])
{
NSLog(#"Spacebar tapped.");
}
else if([string isEqualToString:#""]||(string.length==0))
{
NSLog(#"Backspace tapped.");
}
}
return YES;
}