判断是否textField保留两位小数（或者多位小数）

#pragma mark - UITextField delegate
//textField.text 输入之前的值 string 输入的字符
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

{

BOOL isHaveDian=YES;

    if ([textField.text rangeOfString:@"."].location == NSNotFound) {
        isHaveDian = NO;
    }
    if ([string length] > 0) {
    
        unichar single = [string characterAtIndex:0];//当前输入的字符
        if ((single >= '0' && single <= '9') || single == '.') {//数据格式正确
        
            //首字母不能为0和小数点
            if([textField.text length] == 0){
                if(single == '.') {
                    [self showError:@"亲，第一个数字不能为小数点"];
                    [textField.text stringByReplacingCharactersInRange:range withString:@""];
                    return NO;
                }
                if (single == '0') {
                    [self showError:@"亲，第一个数字不能为0"];
                    [textField.text stringByReplacingCharactersInRange:range withString:@""];
                    return NO;
                }
            }
            
            //输入的字符是否是小数点
            if (single == '.') {
                if(!isHaveDian)//text中还没有小数点
                {
                    isHaveDian = YES;
                    return YES;
                    
                }else{
                    [self showError:@"亲，您已经输入过小数点了"];
                    [textField.text stringByReplacingCharactersInRange:range withString:@""];
                    return NO;
                }
            }else{
                if (isHaveDian) {//存在小数点
                
                    //判断小数点的位数
                    NSRange ran = [textField.text rangeOfString:@"."];
                    if (range.location - ran.location <= 2) {
                        return YES;
                    }else{
                        [self showError:@"亲，您最多输入两位小数"];
                        return NO;
                    }
                }else{
                    return YES;
                }
            }
        }else{//输入的数据格式不正确
            [self showError:@"亲，您输入的格式不正确"];
            [textField.text stringByReplacingCharactersInRange:range withString:@""];
            return NO;
        }
    }
    else
    {
        return YES;
    }
}