A collection of template objects with different template parameters
As a kind of factory-method setup I want to register functors which each create objects of a different type, but meet a common interface - i.e all create objects subclassing a core class.
Say I have something like:
template <class T> struct FactoryMethod
{
X* create();
}
I cannot have (IIRC) std::map<std::string,FactoryMethod*>
because each FactoryMethod
template specialization is a separate type. But I could do:
struct IFactoryMethod
{
virtual X* create()=0;
};
template <class T> struct FactoryMethod : public IFactoryMethod
{
virtual X* 开发者_开发问答create();
};
std::map<std::string,IFactoryMethod*> factories;
Right? I am not aware standard STL has a way to make this neater though I guess boost does - however we don't use boost right now and I am interested anyway.
The idea is then factories
can be looked up based on type-name (read from XML for instance) to create the right type.
This is known as type erasure and is a fairly common idiom- although your map could of course be made of ownership-enforcing pointers and you could also use a virtual destructor like most sane people.
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