• BC (4/4) Nov 21 2007 new question. since IInterface.classinfo returns IInterface, how to get
• Christopher Wright (23/26) Nov 21 2007 Do you have a variable that's passed as IInterface?
• Robert Fraser (7/10) Nov 21 2007 typeid.
• Christopher Wright (2/14) Nov 21 2007 Error: foo is used as a type.
• Ary Borenszweig (3/18) Nov 22 2007 Probably
• Christopher Wright (9/29) Nov 22 2007 Yes, but then you have:
• Robert Fraser (4/19) Nov 22 2007 Oops, shouldn't shoot my mouth off unless I actually know what I'm
• Jarrett Billingsley (5/7) Nov 21 2007 Something to keep in mind is that an interface doesn't necessarily point...

BC <NOTmi_emayl_adrez hotmail.com.remove.not> writes:

new question. since IInterface.classinfo returns IInterface, how to get
the actual value of the concrete class?

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Christopher Wright <dhasenan gmail.com> writes:

BC wrote:
 new question. since IInterface.classinfo returns IInterface, how to get
 the actual value of the concrete class?
 

Do you have a variable that's passed as IInterface?

---
interface IFoo {}
class Foo : IFoo {}
void whatever (IFoo foo) {
    assert (foo.classinfo is Foo.classinfo);
}
---

That should, I think, work. It fails.

I believe that .classinfo is a static field, which is why it fails. It 
needs to be accessed in a virtual way. Since typeof() is compile-time, 
it doesn't help.


You can do the ultra-cruddy way, if you're just looking for equality 
with some known type, which is naturally completely untested:

bool isType!(T)(Object o) {
    auto vtbl = (*(cast(void*[]*)&o))[0];
    return vtbl == T.classinfo.vtbl.ptr;
}

If you have a classinfo dictionary, that doesn't help, unless you start 
storing by vtbl ptr instead.

Of course, Walter's free to change the layout of objects any time he 
wishes, so this is quite version-specific.

Robert Fraser <fraserofthenight gmail.com> writes:

BC wrote:
 new question. since IInterface.classinfo returns IInterface, how to get
 the actual value of the concrete class?
 

typeid.

interface Foo { }
class Bar : Foo { }
// ...
Foo foo = new Bar();
TypeInfo ti = typeid(foo);

Christopher Wright <dhasenan gmail.com> writes:

Robert Fraser wrote:
 BC wrote:
 new question. since IInterface.classinfo returns IInterface, how to get
 the actual value of the concrete class?

 
 typeid.
 
 interface Foo { }
 class Bar : Foo { }
 // ...
 Foo foo = new Bar();
 TypeInfo ti = typeid(foo);

Error: foo is used as a type.

Ary Borenszweig <ary esperanto.org.ar> writes:

Christopher Wright wrote:
 Robert Fraser wrote:
 BC wrote:
 new question. since IInterface.classinfo returns IInterface, how to get
 the actual value of the concrete class?

 typeid.

 interface Foo { }
 class Bar : Foo { }
 // ...
 Foo foo = new Bar();
 TypeInfo ti = typeid(foo);

 
 Error: foo is used as a type.

Probably

typeid(typeof(foo))

Christopher Wright <dhasenan gmail.com> writes:

Ary Borenszweig wrote:
 Christopher Wright wrote:
 Robert Fraser wrote:
 BC wrote:
 new question. since IInterface.classinfo returns IInterface, how to get
 the actual value of the concrete class?

 typeid.

 interface Foo { }
 class Bar : Foo { }
 // ...
 Foo foo = new Bar();
 TypeInfo ti = typeid(foo);

 Error: foo is used as a type.

 
 Probably
 
 typeid(typeof(foo))

Yes, but then you have:

---
void whatever (IFoo foo) {
    writefln(typeof(foo).stringof);
}

whatever(new Foo()); // prints IFoo
---

typeof is strictly compile-time. BC's looking for a runtime check.

Robert Fraser <fraserofthenight gmail.com> writes:

Christopher Wright wrote:
 Robert Fraser wrote:
 BC wrote:
 new question. since IInterface.classinfo returns IInterface, how to get
 the actual value of the concrete class?

 typeid.

 interface Foo { }
 class Bar : Foo { }
 // ...
 Foo foo = new Bar();
 TypeInfo ti = typeid(foo);

 
 Error: foo is used as a type.

Oops, shouldn't shoot my mouth off unless I actually know what I'm 
talking about.

Attempt 2: A series of casts and .classinfo should work.

"Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:

"BC" <NOTmi_emayl_adrez hotmail.com.remove.not> wrote in message 
news:op.t15gsgmttn71h3 hal9000xp...
 new question. since IInterface.classinfo returns IInterface, how to get
 the actual value of the concrete class?

Something to keep in mind is that an interface doesn't necessarily point to 
a D class, which is probably why this information isn't available in the 
general case.