OK, here's what I have now - two templates that are self contained and
work well:
The first uses opDispatch to dispatch to a member. The second is a
simple string function that generates the appropriate code. As discussed
the latter composes but the former doesn't.
mixin template dispatchToMember(alias member, methods...)
{
import std.algorithm : among;
import std.traits : ParameterTypeTuple;
template opDispatch(string sym)
if ((methods.length == 0 || sym.among(methods)))
{
auto ref opDispatch(ParameterTypeTuple!(__traits(getMember,
member, sym)) args)
{
return __traits(getMember, member, sym)(args);
}
}
}
string forwardToMember(string member, string[] funs...)
{
string result = " import std.traits : hasMember,
ParameterTypeTuple;\n";
foreach (fun; funs)
{
result ~= "
static if (hasMember!(typeof("~member~"), `"~fun~"`))
auto "~fun~"(ParameterTypeTuple!(typeof("~member~"."~fun~")) args)
{
return "~member~"."~fun~"(args);
}\n";
}
return result;
}
Andrei
