• Max Samukha (47/47) Jul 26 2007 The problem is to write a generic function that would be able to take

Max Samukha <samukha voliacable.com.removethis> writes:

The problem is to write a generic function that would be able to take
the name of a struct or class data member and return a string
representing the type of that member, both at compile time and at run
time.

I came up with the following (hackish) solution (for dmd 2.003):

// Had to add this to workaround the foreach on tuples bugs
private template Members(T, size_t idx = 0)
{
    static if (idx < T.tupleof.length)
    {
        const char[][] members = ([T.tupleof[idx].stringof]
            ~ Members!(T, idx + 1).members);
        const char[][] types = ([typeof(T.tupleof[idx]).stringof]
            ~ Members!(T, idx + 1).types);
    }
    else
    {
        const char[][] members = [];
        const char[][] types = [];
    }
}

string getMemberType(T)(string memberName)
{
    foreach (i, s; Members!(T).members)
    {
        if (s.length > memberName.length
            && s[$ - memberName.length .. $] == memberName
            && s[$ - memberName.length - 1] == '.')
            return Members!(T).types[i];
    }

    assert(false, "No member "  ~ memberName ~ " for type " ~
T.stringof);
}

class A
{
    char[][] a;
}

void main()
{
   //writefln(a);

   static compileTime = getMemberType!(A)("a");
   auto runTime = getMemberType!(A)("a");

   writefln("Compile time: " ~ compileTime);
   writefln("Run time: " ~ runTime);
}

--------
Does anybody know a better way? Maybe using the new __traits? Thanks.