On Sun, 14 Nov 2010 05:28:29 -0500, Per Ångström <d-n...@autark.se> wrote:
On 2010-11-11 17:21, Steven Schveighoffer wrote:
First, you can't forward-declare classes in one file that are defined in
another file, instead of importing. The reason is because in D, the
module is the namespace that the class is declared in.
So for instance, when you define IStudent in IStudent.d, it's full name
is IStudent.Istudent
if you did something like:
interface IStudent;
in ITeacher.d, then it's full name would be ITeacher.IStudent, not
IStudent.IStudent. So it's not the same.
I get it now. So there is no way out for me: I have to import any module
whose interfaces I use, even though I'm only referring to their names.
Second, you are only having fits about forward declarations because you
aren't used to it :)
Actually, I would say it's the other way around: I am used to them
(being able to refer to an unknown identifier as long as I don't use it)
in C and C++ and find it lacking in D.
I said that wrong, I meant forward *references* not forward
*declrations*. That is, referring to things that aren't declared yet.
> That being said, D has had many forward reference
bugs (I believe there are still a few active ones), so it doesn't always
*just work*. Plus there's the issue of circular imports causing code to
fail at runtime due to module construction dependencies.
But in any case, you shouldn't worry about it, just import away, and the
compiler can take it.
But I still think cutting down on intermodule dependencies is a good
thing, for ease of comprehension and unit testing.
Fortunately, by separating interface and implementation, one can at
least keep the implementation modules free from interdependencies. It's
not perfect but it's not a complete mess either.
It is one way to keep dependencies down. And less dependencies means less
coupling, meaning importing one module doesn't make you import (and
include the code for) many other modules. The compiler isn't yet mature
enough to trim out some code that is never used.
-Steve
