UITextField 如何检查是否按下了删除键

Question

I am implementing a search bar from my local database that searches from db as user enters info.The issue is that i concat recent character and the previous ones and then send it for search.How can I REMOVE the character (last one) when back key is pressed.I am using

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

Thanks for the replies

Answer 1

You can get the string that is supposed to be in text field after this method:

NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string];

And that newString you probably can use 'as is' for searching the database.

If you just want to get the event when user deletes some characters in textField - then you can check it the following way:

if ([string length] == 0 && range.length > 0)
  //Some characters deleted

Answer 2

for swift users:

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {

    if string.characters.count == 0 && range.length > 0 {
        // Back pressed
        return false
    }

    return true
}

Answer 3

Better idea - in textField:shouldChangeCharactersInRange:replacementString: set up a conditional to return NO when there are no more characters...

if ((range.location == 0) && (string.length == 0))
{        
    NSLog(@"is cleared!");
    return NO;
}

return YES;

Answer 4

if (self.textView.text.length > 0) 
{ 
    [self.textView deleteBackward]; 
}