On 23/03/11 03:41, Steven Schveighoffer wrote:
On Mon, 21 Mar 2011 20:12:55 -0400, Nick Sabalausky <[email protected]> wrote:
I'm intending this thread as somewhat of a roundtable-like discussion.
Hopefully we can come up with good material for a short article on
Wiki4D,
or maybe the D website, or wherever.
The scenario: A coder is writing some D, compiles, runs and gets a
"Cyclic
dependency in static ctors" error. Crap! A pain for experienced D
users, and
very bad PR for new D users. (Hopefully we'll eventually get some
sort of
solution for this, but in the meantime D users just have to deal with
it.)
The question: What now? What strategies do people find useful for
dealing
with this? Any specific "first steps" to take? Best practices? Etc.
What one can try is to factor out the initialization code into a
separate module. Essentially if you have:
module a;
import f : someFunction;
import b; // conflicts because of circular dependencies
int aglobal;
static this()
{
aglobal = someFunction();
}
You can do something like:
module a_static;
import f : someFunction;
int aglobal;
static this()
{
aglobal = someFunction();
}
in a.d:
module a;
public import a_static;
import b;
Of course, there can be reprecussions -- you may need to have aglobal
declared in a.d. In those cases, one can try to hide the cycle as Max
Samuckha stated, but I'd rather see a compiler option than these kinds
of workarounds. The workarounds can be unobvious, but can be just as
dangerous.
-Steve
My own solution to this "problem" is to never have circular imports at
all. The build system I use prohibits them, so any careless introduction
of a circularity is spotted immediately and I refactor the code to
eliminate the circularity. I have never come across a valid need for
circularities, and have never had any trouble eliminating any that creep in.
Avoiding circularities has plenty of advantages, like progressive
development, testing and integration. On bigger projects these
advantages are very important, and even on small ones they are useful.
--
Graham St Jack
