Hi, I've been following the D language off and on for several
years, have read Andrei's D book, but haven't ever posted here
before. Mostly, I come from a C++ and C# background. Recently, I
was playing with D using the derelict bindings for the SDL
library.
The SDL library uses handles in the form of struct pointers for
resource management. In C++ I like using unique and shared
pointers to manage C handles. Additionally, I like being able to
specify custom clean up functions for specific resources. For
example:
typedef std::unique_ptr<HandleType, HandleDeleter> handle_ptr;
My question is: what's the status of D's struct Unique? It looks
like struct RefCounted is current, but I can't tell with Unique.
There's several comments in the source that say: doesn't work
yet. It seems like some of it could be made to work as intended.
For example, the commented out code to disallow construction via
an lvalue:
// this(U)(ref Unique!(U) u) = null; // commented out
// this(this) = null;
Couldn't this be written:
@disable this(U)(ref Unique!(U) u);
@disable this(this);
Seems to work when I try it. It stopped the copy from working,
but I can still do a move. Like this:
Unique!(int) i1 = new int;
Unique!(int) i2 = move(i1); // works!
Next, I'd like to be able to use a custom deleter. For example, a
naive implementation I could write would be something like:
struct Unique2(T, string D = "delete")
{
...
~this()
{
debug(Unique2) writeln("Unique destructor of ", (_p is
null)? null: _p);
if (_p !is null)
{
mixin(""~D~" (_p);"); // delete _p;
_p = null;
}
}
...
So, I could do things like:
Unique2!(int, "free") i1 = cast(int*)malloc(int.sizeof); // lame
example
A real implementation would allow more interesting deleters in
the form of delegates, but I'm already stretching my D skillz.
Anyway, am I missing something here? Is there a better D language
feature I'm not thinking about that provides the same
functionality as C++'s std::unique_ptr<> with custom deleters;
besides putting scope (exit) everywhere?
-Chris
