Question on how to convert empty std::tm to timestamp and convert back in a MySQL database

[asmwarrior]

Question on how to convert empty std::tm to timestamp and convert back in a MySQL database

[asmwarrior]

It looks like I can't compare the if (row.timestamp == std::tm()), so I change the code like below:

bool IsTmEmpty(const std::tm& time) {
    return (time.tm_year == 0 &&
            time.tm_mon == 0 &&
            time.tm_mday == 0 &&
            time.tm_hour == 0 &&
            time.tm_min == 0 &&
            time.tm_sec == 0);
}

And later, I use such code:

    static void to_base(const MyClass& row, values& v, indicator& ind)
    {
        v.set("id", row.id);
        
        // check to see whether the row.timestamp is an empty null "std::tm", if true, set the field value as NULL
        if ( IsTmEmpty(row.timestamp) )
        {
            v.set("timestamp", soci::i_null);
        }
        else
        {
            v.set("timestamp", row.timestamp);
        }

        ind = i_ok;
    }

But sadly, the above code still can't be built. The issue happens here: v.set("timestamp", soci::i_null);, I'm currently don't know how to use the null indicator.

Thanks.

[asmwarrior]

OK, I think I found the solution, it is inside the document:

See here:

https://github.com/SOCI/soci/blob/884808c294e4809064650f3e5aed9102d8a68d56/docs/types.md?plain=1#L303C1-L303C73

So, the final code which works is like below:

    static void to_base(const MyClass& row, values& v, indicator& ind)
    {
        v.set("id", row.id);

        // check to see whether the row.timestamp is an empty null "std::tm", if true, set the field value as NULL
        v.set("timestamp", row.timestamp, IsTmEmpty(row.timestamp) ? i_null : i_ok);

        ind = i_ok;
    }