iOS UITextField输入限制长度

#pragma mark - <UITextFieldTextDidChangeNotification>
- (void)textFieldNotification:(NSNotification *)note {
    
    UITextField *textField = note.object;
    NSString *lang = [[UITextInputMode currentInputMode] primaryLanguage];
    if ([lang isEqualToString:@"zh-Hans"]) {
        
        UITextRange *selectedRange = [textField markedTextRange];
        UITextPosition *position = [textField positionFromPosition:selectedRange.start offset:0];
        if (!position) {
            
            if (textField.text.length > 4) {
                
                textField.text = [textField.text substringToIndex:4];
            }
        }
    } else {
        
        if (textField.text.length > 4) {
            
            textField.text = [textField.text substringToIndex:4];
        }
    }
}