C++0x class factory with variadic templates problem
- by randomenglishbloke
I have a class factory where I'm using variadic templates for the c'tor parameters (code below). However, when I attempt to use it, I get compile errors; when I originally wrote it without parameters, it worked fine.
Here is the class:
template< class Base, typename KeyType, class... Args >
class GenericFactory
{
public:
GenericFactory(const GenericFactory&) = delete;
GenericFactory &operator=(const GenericFactory&) = delete;
typedef Base* (*FactFunType)(Args...);
template <class Derived>
static void Register(const KeyType &key, FactFunType fn)
{
FnList[key] = fn;
}
static Base* Create(const KeyType &key, Args... args)
{
auto iter = FnList.find(key);
if (iter == FnList.end())
return 0;
else
return (iter->second)(args...);
}
static GenericFactory &Instance() { static GenericFactory gf; return gf; }
private:
GenericFactory() = default;
typedef std::unordered_map<KeyType, FactFunType> FnMap;
static FnMap FnList;
};
template <class B, class D, typename KeyType, class... Args>
class RegisterClass
{
public:
RegisterClass(const KeyType &key)
{
GenericFactory<B, KeyType, Args...>::Instance().Register(key, FactFn);
}
static B *FactFn(Args... args)
{
return new D(args...);
}
};
Here is the error: when calling (e.g.)
// Tucked out of the way
RegisterClass<DataMap, PDColumnMap, int, void *> RC_CT_PD(0);
GCC 4.5.0 gives me:
In constructor 'RegisterClass<B, D, KeyType, Args>::RegisterClass(const KeyType&) [with B = DataMap, D = PDColumnMap, KeyType = int, Args = {void*}]':
no matching function for call to 'GenericFactory<DataMap, int, void*>::Register(const int&, DataMap* (&)(void*))'
I can't see why it won't compile and after extensive googling I couldn't find the answer. Can anyone tell me what I'm doing wrong (aside from the strange variable name, which makes sense in context)?
