On Sunday, 26 May 2013 at 14:19:13 UTC, mimi wrote:
Hi!
I am want to get list of fields types and offsets in struct by
the template.
I.e., lookup through this struct:
struct S {
int a;
string b;
someptr* c;
};
template Lookup!( S )(); returns something as:
field #0, int, offset 0
field #1, string, offset 8,
field #2, someptr, offset 16
How I can do this?
To get a TypeTuple containing this information you can do this:
template Lookup(S)
{
template Field(int index_, Type_, int offset_)
{
enum index = index_;
alias Type = Type_;
enum offset = offset_;
}
template impl(int i)
{
static if(i == S.tupleof.length)
alias impl = TypeTuple!();
else
alias impl = TypeTuple!(
Field!(i, typeof(S.tupleof[i]),
S.init.tupleof[i].offsetof),
impl!(i + 1));
}
alias Lookup = impl!0;
}
If you only want to format this information to a string it's even
simpler:
string lookup(S)()
{
auto r = "";
S s;
foreach(i, e; s.tupleof)
r ~= xformat("field #%s, %s, offset %s\n",
i, typeof(s.tupleof[i]).stringof,
s.tupleof[i].offsetof);
return r;
}
Then lookup!S will give you the string and you can use it at
compile time or at run time.
