Re: Interface file

[Jan Johansson via Digitalmars-d]

On Wednesday, 30 September 2015 at 18:01:57 UTC, Adam D. Ruppe 
wrote:
On Wednesday, 30 September 2015 at 17:51:50 UTC, Jan Johansson 
wrote:
The interface file (I called it test.di):

FYI there's no actual difference between .di files and .d 
files. The way D is meant to be used is you write the 
declarations together, then if you want to, you can 
automatically strip the bodies out of a .d file (dmd -H does 
it) and that makes the .di file.


But you always substitute the .di file for the .d file with the 
same name. They cannot be used together like a .h and .cpp file.


You can put an interface in a separate module than a class. 
Then you import the interface module from both locations, 
though your factory function won't work like that.

Try something like:

itest.d:

module itest;
interface IMyTest {
  void Write(string message);
}

test.d:

public import itest; // import the interface definition too
import std.stdio;

private class MyTest : IMyTest {
    void Write(string message) {
        writeln(message);
    }
}

public IMyTest createInstance() {
    return new MyTest;
}



main.d:

import test;
import std.stdio;

 void main() {
     auto p = createInstance();
     p.Write("Hello, World!");
 }



And that should work.

  dmd test.d test.di -lib -oftest

would be more like `dmd itest.d test.d -lib -oftest`

  dmd main.d test.di test.a

and `dmd main.d itest.d test.a`



Or you could just compile it all at once with `dmd main.d 
test.d itest.d`

Thanks,

But (there is always a but) ;-)

The main.d should rely on itest.d, not test.d, otherwise I do the 
declaration for the library itself, but the main.d includes the 
test.d - the implementation (not the declaration).

If I change the 'dmd main.d test.d test.a' to 'dmd main.d itest.d 
test.a', then I got a new error: itest.d:(.text._Dmain+0x5): 
undefined reference to `_D5itest14createInstanceFZC5itest7IMyTest'

The linker get confused about the separation of the declaration 
and implementation.

Best regards
Jan Johansson