• Qian Xu (8/8) Jan 21 2009 Hi All,
• Qian Xu (8/20) Jan 21 2009 what I have found is:
• Frits van Bommel (5/12) Jan 21 2009 if (is(class_A : intf_B))
• Qian Xu (8/21) Jan 21 2009 Thanks. Could you tell me, how to make a function for this? I do not kno...
• Trass3r (7/15) Jan 21 2009 Guess something like
• BCS (5/40) Jan 21 2009 if you want to check if an instance of C1 is a derived class that implem...
• Jarrett Billingsley (6/13) Jan 21 2009 At compile time, like Frits said, you can use is(class_A : intf_B).

Qian Xu <quian.xu stud.tu-ilmenau.de> writes:

Hi All,

can D check, whether a class A an Interface B supports?

like:

  if (supports(class_A, intf_B))
  {
     cast(intf_B) (class_A).hello();
  }

--Qian

Qian Xu <quian.xu stud.tu-ilmenau.de> writes:

Qian Xu wrote:

 Hi All,
 
 can D check, whether a class A an Interface B supports?
 
 like:
 
   if (supports(class_A, intf_B))
   {
      cast(intf_B) (class_A).hello();
   }
 
 --Qian

what I have found is:

  if (is(class_A == intf_B))
  {
    cast(intf_B) (class_A).hello();
  }

Is there any better one?

--Qian

Frits van Bommel <fvbommel REMwOVExCAPSs.nl> writes:

Qian Xu wrote:
 Hi All,
 
 can D check, whether a class A an Interface B supports?
 
 like:
 
   if (supports(class_A, intf_B))

     if (is(class_A : intf_B))
tests if 'class_A' is implicitly convertible to 'intf_B'. If the first 
is a class and the second an interface, that's equivalent to the class 
implementing the interface.

Qian Xu <quian.xu stud.tu-ilmenau.de> writes:

Frits van Bommel wrote:

 Qian Xu wrote:
 Hi All,
 
 can D check, whether a class A an Interface B supports?
 
 like:
 
   if (supports(class_A, intf_B))

 
      if (is(class_A : intf_B))
 tests if 'class_A' is implicitly convertible to 'intf_B'. If the first
 is a class and the second an interface, that's equivalent to the class
 implementing the interface.

Thanks. Could you tell me, how to make a function for this? I do not know
how to pass an Interface as parameter.

like
  bool supports(T)(T obj, interface_type t)
  {
    return (is(obj : t));
  }

Trass3r <mrmocool gmx.de> writes:

Qian Xu schrieb:
 Thanks. Could you tell me, how to make a function for this? I do not know
 how to pass an Interface as parameter.
 
 like
   bool supports(T)(T obj, interface_type t)
   {
     return (is(obj : t));
   }

Guess something like

bool supports(T, I) (T obj)
{
	return (is(obj : I));
}

should do it.

BCS <ao pathlink.com> writes:

Reply to Qian,

 Frits van Bommel wrote:
 
 Qian Xu wrote:
 
 Hi All,
 
 can D check, whether a class A an Interface B supports?
 
 like:
 
 if (supports(class_A, intf_B))
 

 if (is(class_A : intf_B))
 tests if 'class_A' is implicitly convertible to 'intf_B'. If the
 first
 is a class and the second an interface, that's equivalent to the
 class
 implementing the interface.

 Thanks. Could you tell me, how to make a function for this? I do not
 know how to pass an Interface as parameter.
 
 like
 bool supports(T)(T obj, interface_type t)
 {
 return (is(obj : t));
 }

Given 

 interface I {}
 class C1 {}
 class C2 : C1, I {}
 class C3 : C1 {}

if you want to check if an instance of C1 is a derived class that implements 
I use this

 null !is cast(I)c1

if you want it in a function

 bool IsA(TI, TC)(TC c)
 {
   return null !is cast(TI)c;
 }

Jarrett Billingsley <jarrett.billingsley gmail.com> writes:

On Wed, Jan 21, 2009 at 10:30 AM, Qian Xu <quian.xu stud.tu-ilmenau.de> wrote:
 Hi All,

 can D check, whether a class A an Interface B supports?

 like:

  if (supports(class_A, intf_B))
  {
     cast(intf_B) (class_A).hello();
  }

At compile time, like Frits said, you can use is(class_A : intf_B).

At runtime, you can use cast(intf_B)someInstance.  That returns 'null'
if someInstance does _not_ inherit from intf_B.

if(auto i = cast(intf_B)instanceOfA)
    i.hello();