On Tue, 01 Apr 2014 03:31:41 -0400, Frustrated <w...@where.com> wrote:
Basically in programming to interfaces I need to decide to call a
virtual method of an object if it exists else call a final method in the
interface:
interface A
{
static final void foo() { ... }
}
class B : A
{
void bar() { ... } // optional
}
class C : B
{
void bar() { ... } // optional
}
void main()
{
A a = new B; // or new C;
// if a.bar exists call it, else call foo
// code should work independent of the classes. (there might be
more)
}
The point of the code is simply to allow the class to implement bar
optionally but provide default behavior with foo. I need a way to
dynamically determine if bar exists and fall back on foo. This should be
possible.
e.g., suppose
class B : A { }
then I would like to b.bar() to actually call A.foo() (since bar doesn't
exist in b).
I guess the exist way would be to create an opDispatch and have it call
foo if bar is passed. This works great and does everything I need it to
except requires adding the code in the class which I can't have. Also
I'm not sure how it would work with virtual methods.
Detecting whether bar exists can only happen at compile time, since an
instance of A has no mechanism to detect whether it has bar. D does not
have very good runtime introspection, that would have to be built into the
TypeInfo struct (the mechanism exists to do it, but it has never been used
for that).
You could use this templates, but that would only work if the type of the
derived class is known at compile time.
This problem could easily be solved by virtual methods with default
implementation.
-Steve
