我正在閱讀庫的源代碼。但我不明白這個模板定義如何工作的:我不明白這個C++模板如何工作
template <class A>
struct Use{
template <class T> struct AsVertexType: public T{typedef A VertexType; typedef VertexType * VertexPointer ;};
template <class T> struct AsEdgeType: public T{typedef A EdgeType; typedef EdgeType * EdgePointer ;};
template <class T> struct AsFaceType: public T{typedef A FaceType; typedef FaceType * FacePointer ;};
template <class T> struct AsTetraType: public T{typedef A TetraType; typedef TetraType * TetraPointer ;};
template <class T> struct AsHEdgeType: public T{typedef A HEdgeType; typedef HEdgeType * HEdgePointer ;};
};
這是如何使用使用<到declaire類>模板:
struct MyUsedTypes : public vcg::UsedTypes< vcg::Use<MyVertex> :: AsVertexType,
vcg::Use<MyEdge> :: AsEdgeType,
vcg::Use<MyFace> :: AsFaceType> {};
在使用<>模板定義,有兩個未知類型A和T.
以vcg::Use<MyVertex>::AsVertexType
爲例,我認爲A是MyVertex,但什麼是T?
補充
這裏是模板UsedTypes
template < template <typename> class A = DefaultDeriver, template <typename> class B = DefaultDeriver,
template <typename> class C = DefaultDeriver, template <typename> class D = DefaultDeriver,
template <typename> class E = DefaultDeriver, template <typename> class F = DefaultDeriver,
template <typename> class G = DefaultDeriver, template <typename> class H = DefaultDeriver >
class UsedTypes
: public Arity12<DummyTypes,
Use< Vertex< UsedTypes<A, B, C, D , E, F, G, H> > > :: template AsVertexType,
Use< Edge < UsedTypes<A, B, C, D , E, F, G, H> > > :: template AsEdgeType,
Use< Face < UsedTypes<A, B, C, D , E, F, G, H> > > :: template AsFaceType,
Use< HEdge < UsedTypes<A, B, C, D , E, F, G, H> > > :: template AsHEdgeType,
A, B, C, D, E, F, G, H > {};
等一系列元數模板定義的定義。這就像一個數學歸納法
template < class Base,
template <typename> class A >
class Arity1: public A<Base> {};
template < class Base,
template <typename> class A,
template <typename> class B >
class Arity2: public B<Arity1<Base, A>> {};
template < class Base,
template <typename> class A, template <typename> class B,
template <typename> class C >
class Arity3: public C<Arity2<Base, A, B>> {};
.
.
.
template < class Base,
template <typename> class A, template <typename> class B,
template <typename> class C, template <typename> class D,
template <typename> class E, template <typename> class F,
template <typename> class G, template <typename> class H,
template <typename> class I, template <typename> class J,
template <typename> class K, template <typename> class L >
class Arity12: public L<Arity11<Base, A, B, C, D, E, F, G, H, I, J, K>> {};
現在還很難說,模板參數T是什麼。
完整源代碼,請。 – curiousguy