Re: Assigning Interface to Object
"Andrej Mitrovic" wrote in message news:mailman.764.1295584412.4748.digitalmars-d-le...@puremagic.com... > Speaking of COM.. has anyone successfully used COM interfaces in D2? > I'm asking because a few months ago I gave them a try but I kept > having random access violations. And I *do* mean random, sometimes > adding/removing print statements that don't even touch the state of > the program would cause a crash. I couldn't even transfer the D1 COM > example to D2, even though the D1 example works fine. > > I might have to investigate this further soon. Yes, mostly with DirectX. One problem I think I ran into was that I found more then one definiton of IUnknown, and only one made derived interfaces COM interfaces.
Re: Assigning Interface to Object
"Mandeep Singh Brar" wrote in message news:ihf3gs$2kve$1...@digitalmars.com... > Hi, > > I was just thinking if implementing interfaces as abstract classes could > be a workaround. Since D anyways allows multiple inheritance, so would it > make sense > to just declare interfaces as abstract classes. Would there be any reason > not to do that. > > Thanks & Regards > Mandeep The big one is that D _doesn't_ allow multiple inheritance.
Re: Assigning Interface to Object
Hi, I was just thinking if implementing interfaces as abstract classes could be a workaround. Since D anyways allows multiple inheritance, so would it make sense to just declare interfaces as abstract classes. Would there be any reason not to do that. Thanks & Regards Mandeep
Re: Assigning Interface to Object
Speaking of COM.. has anyone successfully used COM interfaces in D2? I once tried to create a DDraw proxy dll but I can't remember how good it worked. https://bitbucket.org/trass3r/ddrawproxy
Re: Assigning Interface to Object
Speaking of COM.. has anyone successfully used COM interfaces in D2? I'm asking because a few months ago I gave them a try but I kept having random access violations. And I *do* mean random, sometimes adding/removing print statements that don't even touch the state of the program would cause a crash. I couldn't even transfer the D1 COM example to D2, even though the D1 example works fine. I might have to investigate this further soon.
Re: Assigning Interface to Object
On Thu, 20 Jan 2011 02:01:26 -0500, Mandeep Singh Brar wrote: "This would be easily resolved if interfaces were known to be Objects. " But shouldnt this be the case, because there would be nothing called as an Interface which can be pointed to; it would be an Object which is implementing an interface which is being pointed to. So shouldnt Interfaces be Objects too. Otherwise, wouldnt it defeat the purpose of having Object as the base class for everything. The issue is COM interfaces. What bugs me about it is, whether an interface derives from IUnknown is known at compile time. I don't think it's possible to define an interface that *doesn't* derive from IUnknown that is not a D Object. I believe the compiler even handles IUnknown interfaces differently. I think the problem is that COM support was added when compile-time functionality was in its infancy. There are quite a few legacy problems due to that. For instance, the builtin array sort routine does not use compile-time information. It would be nice to fix this problem, but I'm not sure how willing Walter is to do it. For sure, we need a solution to the opEquals problem. -Steve
Re: Assigning Interface to Object
> Object is only the base class for all D classes. Interfaces may also > represent COM objects or C++ classes, which are not subclasses of Object. Can't the compiler check if it is a normal D interface and then allow (implicit) casts to Object?
Re: Assigning Interface to Object
Mandeep Singh Brar wrote: "This would be easily resolved if interfaces were known to be Objects. " But shouldnt this be the case, because there would be nothing called as an Interface which can be pointed to; it would be an Object which is implementing an interface which is being pointed to. So shouldnt Interfaces be Objects too. Otherwise, wouldnt it defeat the purpose of having Object as the base class for everything. Object is only the base class for all D classes. Interfaces may also represent COM objects or C++ classes, which are not subclasses of Object. -- Simen
Re: Assigning Interface to Object
On 01/20/11 01:01, Mandeep Singh Brar wrote: > "This would be easily resolved if interfaces were known to be Objects. " > > But shouldnt this be the case, because there would be nothing called as an > Interface which can be pointed to; it would be an Object which is > implementing an > interface which is being pointed to. So shouldnt Interfaces be Objects too. > Otherwise, wouldnt it defeat the purpose of having Object as the base class > for > everything. > > Thanks > Mandeep There are actually Interfaces which don't necessarily imply inheritance from Object. The canonical example being IUnknown and it's own descendants, used for interacting with COM libraries. Another example -- as I understand the implementation at least -- are 'extern(C++)' interfaces, which are really API declarations for C++ classes. That said, these are special cases, and I would expect the assertion that interface <- Object to be true in all other cases. -- Chris N-S
Re: Assigning Interface to Object
> interface I {}
>
> ...
>
> I a = ...;
> I b = ...;
>
> if (a == b) //<-- ERROR
"1.065: compiles without error, though it seems to be equivalent to is
2.051: it's really weird "
I would guess this should be filed as a bug then.
Thanks
Mandeep
Re: Assigning Interface to Object
"This would be easily resolved if interfaces were known to be Objects. " But shouldnt this be the case, because there would be nothing called as an Interface which can be pointed to; it would be an Object which is implementing an interface which is being pointed to. So shouldnt Interfaces be Objects too. Otherwise, wouldnt it defeat the purpose of having Object as the base class for everything. Thanks Mandeep
Re: Assigning Interface to Object
Steven Schveighoffer wrote:
Nope. try it:
interface I { bool opEquals(I other); }
I a;
I b;
a == b; // same error.
The problem is that when TDPL was implemented, (Object)a == (Object)b
was redefined from a.opEquals(b) to object.opEquals(a, b), where object
is the module object.
That function's signature looks like this:
bool opEquals(Object lhs, Object rhs);
For some reason the compiler tries to do the same thing with interfaces,
but of course, there is no opEquals for your specific interface in
object. Even if there was, you'd likely get an overload error.
This would be easily resolved if interfaces were known to be Objects.
There's another way that should work, replacing the global opEquals in
object.di with this:
equals_t opEquals(T, U)(T lhs, U rhs)
if ((is(T == class) || is(T == interface)) && (is(U == class) || is(U
== interface)))
{
if (lhs is rhs)
return true;
if (lhs is null || rhs is null)
return false;
static if (__traits(compiles,{lhs.opEquals(rhs);}))
{
if (typeid(lhs) == typeid(rhs))
return lhs.opEquals(rhs);
static if (__traits(compiles,{lhs.opEquals(rhs) &&
rhs.opEquals(lhs);}))
{
return lhs.opEquals(rhs) &&
rhs.opEquals(lhs);
}
else static assert( false, T.stringof ~ " cannot be compared to a
" ~ U.stringof );
}
else static assert( false, T.stringof ~ " cannot be compared to a " ~
U.stringof );
}
There are some problems, however. This generates bloat, as instantiations
are created for each combination of types compared. Also, it is only tested
for a few simple cases.
--
Simen
Re: Assigning Interface to Object
On Sun, 16 Jan 2011 08:11:45 -0500, Stewart Gordon
wrote:
On 16/01/2011 08:23, "Jérôme M. Berger" wrote:
Stewart Gordon wrote:
On 15/01/2011 17:44, Steven Schveighoffer wrote:
Which unnecessarily complicates things. For example, you can't compare
two interfaces (try it!).
?
interface I {}
...
I a = ...;
I b = ...;
if (a == b) //<-- ERROR
1.065: compiles without error, though it seems to be equivalent to is
2.051: it's really weird
--
C:\Users\Stewart\Documents\Programming\D\Tests>dmd interface_equals.d
interface_equals.d(7): Error: function object.opEquals (Object lhs,
Object rhs)
is not callable using argument types (I,I)
interface_equals.d(7): Error: cannot implicitly convert expression (a)
of type i
nterface_equals.I to object.Object
interface_equals.d(7): Error: cannot implicitly convert expression (b)
of type i
nterface_equals.I to object.Object
--
Of course, if the interface declares an opEquals, it's a whole different
story
Nope. try it:
interface I { bool opEquals(I other); }
I a;
I b;
a == b; // same error.
The problem is that when TDPL was implemented, (Object)a == (Object)b was
redefined from a.opEquals(b) to object.opEquals(a, b), where object is the
module object.
That function's signature looks like this:
bool opEquals(Object lhs, Object rhs);
For some reason the compiler tries to do the same thing with interfaces,
but of course, there is no opEquals for your specific interface in
object. Even if there was, you'd likely get an overload error.
This would be easily resolved if interfaces were known to be Objects.
-Steve
Re: Assigning Interface to Object
Stewart Gordon wrote: Of course, if the interface declares an opEquals, it's a whole different story It is? Can't seem to get it to work here, and I get the same errors you get. -- Simen
Re: Assigning Interface to Object
On 16/01/2011 08:23, "Jérôme M. Berger" wrote:
Stewart Gordon wrote:
On 15/01/2011 17:44, Steven Schveighoffer wrote:
Which unnecessarily complicates things. For example, you can't compare
two interfaces (try it!).
?
interface I {}
...
I a = ...;
I b = ...;
if (a == b) //<-- ERROR
1.065: compiles without error, though it seems to be equivalent to is
2.051: it's really weird
--
C:\Users\Stewart\Documents\Programming\D\Tests>dmd interface_equals.d
interface_equals.d(7): Error: function object.opEquals (Object lhs,
Object rhs)
is not callable using argument types (I,I)
interface_equals.d(7): Error: cannot implicitly convert expression (a)
of type i
nterface_equals.I to object.Object
interface_equals.d(7): Error: cannot implicitly convert expression (b)
of type i
nterface_equals.I to object.Object
--
Of course, if the interface declares an opEquals, it's a whole different
story
Stewart.
Re: Assigning Interface to Object
Stewart Gordon wrote:
> On 15/01/2011 17:44, Steven Schveighoffer wrote:
>
>> Which unnecessarily complicates things. For example, you can't compare
>> two interfaces (try it!).
>
> ?
interface I {}
...
I a = ...;
I b = ...;
if (a == b) // <-- ERROR
--
mailto:jeber...@free.fr
http://jeberger.free.fr
Jabber: jeber...@jabber.fr
signature.asc
Description: OpenPGP digital signature
Re: Assigning Interface to Object
On 01/15/11 10:34, Simen kjaeraas wrote:
> Mandeep Singh Brar wrote:
>
>> Hi,
>>
>> I am not able to assign an interface to object. The following code
>> does not compile.
>>
>> module testObj;
>>
>> public interface testInterface {
>> void someMethod();
>> }
>> public class testObj
>> {
>> Object someCaller;
>> this(Object caller) {
>> someCaller = caller;
>> }
>> this(testInterface tI, bool xyz) {
>> someCaller = tI;
>> }
>> }
>>
>> Shouldn't this work?
>
> Nope. D allows interfaces to be special in certain cases (notably COM,
> though other may be added in the future), and this precludes making
> interfaces implicitly castable to Object.
>
I believe interfaces marked 'extern(C++)' (for using classes defined by
C++) are also somewhat special.
Still, one would think that the special cases (IUnknown and extern(C++))
would be enforced without affecting "typical" interfaces. Or is there
something about how D's vtbl and other affairs are laid out that I don't
know about -- such that casting from an interface to Object would lose
something?
-- Chris N-S
Re: Assigning Interface to Object
On 15/01/2011 17:44, Steven Schveighoffer wrote: Which unnecessarily complicates things. For example, you can't compare two interfaces (try it!). ?
Re: Assigning Interface to Object
On Sat, 15 Jan 2011 11:34:05 -0500, Simen kjaeraas
wrote:
Mandeep Singh Brar wrote:
Hi,
I am not able to assign an interface to object. The following code
does not compile.
module testObj;
public interface testInterface {
void someMethod();
}
public class testObj
{
Object someCaller;
this(Object caller) {
someCaller = caller;
}
this(testInterface tI, bool xyz) {
someCaller = tI;
}
}
Shouldn't this work?
Nope. D allows interfaces to be special in certain cases (notably COM,
though other may be added in the future), and this precludes making
interfaces implicitly castable to Object.
Which unnecessarily complicates things. For example, you can't compare
two interfaces (try it!).
Sorry, had to get my dig in there :P
-Steve
Re: Assigning Interface to Object
Trass3r wrote:
module testObj;
public interface testInterface {
void someMethod();
}
public class testObj
{
Object someCaller;
this(Object caller) {
someCaller = caller;
}
this(testInterface tI, bool xyz) {
someCaller = tI;
}
}
Shouldn't this work?
Doesn't really make sense.
If you cast it to Object you "loose" the interface methods.
Same way you lose methods of a subclass when you cast it to
a base class. That's allowed, though.
--
Simen
Re: Assigning Interface to Object
Mandeep Singh Brar wrote:
Hi,
I am not able to assign an interface to object. The following code
does not compile.
module testObj;
public interface testInterface {
void someMethod();
}
public class testObj
{
Object someCaller;
this(Object caller) {
someCaller = caller;
}
this(testInterface tI, bool xyz) {
someCaller = tI;
}
}
Shouldn't this work?
Nope. D allows interfaces to be special in certain cases (notably COM,
though other may be added in the future), and this precludes making
interfaces implicitly castable to Object.
--
Simen
Re: Assigning Interface to Object
But it is for only storage purposes. I can cast it back to the Interface later when required. Thanks Mandeep
Re: Assigning Interface to Object
module testObj;
public interface testInterface {
void someMethod();
}
public class testObj
{
Object someCaller;
this(Object caller) {
someCaller = caller;
}
this(testInterface tI, bool xyz) {
someCaller = tI;
}
}
Shouldn't this work?
Doesn't really make sense.
If you cast it to Object you "loose" the interface methods.
Assigning Interface to Object
Hi,
I am not able to assign an interface to object. The following code
does not compile.
module testObj;
public interface testInterface {
void someMethod();
}
public class testObj
{
Object someCaller;
this(Object caller) {
someCaller = caller;
}
this(testInterface tI, bool xyz) {
someCaller = tI;
}
}
Shouldn't this work?
Thanks & Regards
Mandeep
