Re: Passing a module in a template parameter list to __traits(allMembers, module)

[Ali Çehreli]

On 02/26/2013 11:03 AM, Ben Gertzfield wrote:
Hi folks,
In preparation for my upcoming talk at DConf 2013, I'm working on a
compile-time dependency injection prototype for D.

I'd like part of public interface for this system to take a module at
compile time, and return a list of the classes in that module. Something
like:

string GetMembers(T)() {
auto members = [__traits(allMembers, T)];
return join(result, ", ");
}

If I pass a module to __traits(allMembers, foo.bar) outside a template
parameter list, it works great, but as soon as I pass it through a
template parameter list, I get an odd error:

Error: template instance GetMembers!(std) GetMembers!(std) does not
match template declaration GetMembers(T)()

Here's the code I'm working on. Any thoughts on whether this is
possible, and if so, what I'm doing wrong?

http://pastebin.com/BgZ67h8P

Thanks,

Ben

Hi Ben, I am in the same boat and I am about to post questions here 
about code problems. :)

Your first code works with three modifications:

1) std.stdio is not a type, so the template parameter list cannot be 
(T). I used 'alias'.

2) For syntax reasons, you must parenthesize (std.stdio) when passing as 
a template parameter

3) (You couldn't get to this yet.) A typo: result -> members

import std.array;
import std.stdio;
import std.traits;

string GetMembers(alias T)() {
  auto members = [__traits(allMembers, T)];
  return join(members, ", ");
}

void main() {
    stdout.writefln("Got members: %s", GetMembers!(std.stdio));
}

Ali