Re: has_interface trait
On 22 Mai, 00:09, pfultz2 wrote:
[...]
Now say I have two classes like this:
class A
{
public:
void foo()
{
printf("foo is called\n");
}
};
class B
{
};
[...]
So i would like to create a trait to query whether [T has a
member function foo or not], something like this:
bool aHas = has_interface<A>::value; //True
bool bHas = has_interface<B>::value; //False
[...]
I though maybe i could use SFINAE to do this, but I cant figure out a
way to deduce this. Perhaps there is another way to do this. Basically
if it throws a compiler error on constructing the interface, i want it
to return a false value. Does any have any ideas?
I'm not sure whether it's possible in C++03. But In C++0x this should
work:
typedef char one;
typedef char (&two)[2];
template<class T> T&& declval();
template<class T>
struct has_foo_member {
template<class U, class = decltype(declval<U>().foo()) >
static one test(U*);
static two test(...);
static const bool value = sizeof(test(declval<T*>()))==1;
};
unless some foo member function is private in which case you'll get a
compile-time error anyway.
Cheers,
SG
--
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
[ comp.lang.c++.moderated. First time posters: Do this! ]