UITextField限制小数点后两位

//textField.text 输入之前的值 string 输入的字符
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    self.waitPayLabel.text = [NSString stringWithFormat:@"待支付¥%@ |优惠¥%@",self.totalTF.text,self.exclusiveMoneyTF.text];

    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 == '.')
                {
                    [textField.text stringByReplacingCharactersInRange:range withString:@""];
                    return NO;
                }
                if (single == '0')
                {
                }
            }
            
            if([textField.text length]==1)
            {
            
                NSString *first = [textField.text substringToIndex:1];//字符串开始
                if ([first isEqualToString:@"0"])//首字母是0的时候
                {
                    if(single == '.')
                    {
                        isHaveDian=YES;
                        return YES;
                    }
                    else
                    {
                        [textField.text stringByReplacingCharactersInRange:range withString:@""];
                        return NO;
                    }
                }
                else
                {
                    return YES;
                }
            }
            if (single=='.')
            {
                if(!isHaveDian)//text中还没有小数点
                {
                    isHaveDian=YES;
                    return YES;
                }else
                {
                    [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:@"."];
                    int tt=range.location-ran.location;
                    if (tt <= 2)
                    {
                        return YES;
                    }
                    else
                    {
                        return NO;
                    }
                }
                else
                {
                    return YES;
                }
            }
        }else
        {
            //输入的数据格式不正确
            [textField.text stringByReplacingCharactersInRange:range withString:@""];
            return NO;
        }
    }
    else
    {
        return YES;
    }
}