在 UITextField 中添加删除绑定（绑定删除）

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    if (string.length != 0) {
        return YES;
    }
    if (self.quoteText.length == 0) { // quoteText 就是目标字符串
        return YES;
    }
    // 计算当前光标相对于文本开始位置的偏移量
    NSInteger cursorOffset = [textField offsetFromPosition:textField.beginningOfDocument toPosition:textField.selectedTextRange.start];
    
    NSRange foundRange = [textField.text rangeOfString:self.quoteText];
    if (foundRange.location != NSNotFound) {
        if (foundRange.location <= cursorOffset &&
            foundRange.length + foundRange.location >= cursorOffset) {
            
            textField.text = [textField.text stringByReplacingCharactersInRange:foundRange withString:@""];
            // 光标移动到删除时的位置
            UITextPosition *beginPosition = [textField positionFromPosition:textField.beginningOfDocument offset:foundRange.location];
            UITextRange *newRange = [textField textRangeFromPosition:beginPosition toPosition:beginPosition];
            [textField setSelectedTextRange:newRange];
            
            return NO;
        }
        return YES;
    } else {
        return YES;
    }
}