- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
    //刪除處理
    if ([string isEqualToString:@""]) {
        return YES;
    }
    //首位不能為.號
    if (range.location == 0 && [string isEqualToString:@"."]) {
        return NO;
    }
    return [self isRightInPutOfString:textField.text withInputString:string range:range];
}


- (BOOL)isRightInPutOfString:(NSString *) string withInputString:(NSString *) inputString range:(NSRange) range{
    //判斷只輸出數(shù)字和.號
    NSString *passWordRegex = @"[0-9\\.]";
    NSPredicate *passWordPredicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",passWordRegex];
    if (![passWordPredicate evaluateWithObject:inputString]) {
        return NO;
    }
    //邏輯處理
    if ([string containsString:@"."]) {
        if ([inputString isEqualToString:@"."]) {
            return NO;
        }
        //限制兩位小數(shù)
        NSRange subRange = [string rangeOfString:@"."];
        if (range.location - subRange.location > 2) {
            return NO;
        }
    }
    return YES;
}