C++委托库实现之TypeLength

QLib::Event委托库下载 http://upload.programfan.com/upfile/200548160qevent.rar

QLib::Event委托库支持0-9参数的任意委托声明。

QLib::Event<void> ev0;

QLib::Event<int,int> ev1;

QLib::Event<int,int,int> ev2;

实现核心为TypeLength - 推导实际输入的参数个数。

struct NullType;

template <typename T1 = NullType, typename T2 = NullType, typename T3 = NullType, typename T4 = NullType, typename T5 = NullType, typename T6 = NullType, typename T7 = NullType, typename T8 = NullType, typename T9 = NullType>

struct Length

{

template <typename T1 = NullType>

struct Len

{

enum{value = 1};

};

template<>

struct Len<NullType>

{

enum {value = 0};

};

enum enum_len {value = Len<T1>::value + Len<T2>::value+Len<T3>::value+Len<T4>::value+Len<T5>::value+Len<T6>::value+Len<T7>::value+Len<T8>::value+Len<T9>::value};

};

利用Length::value可以得到实际输入的参数个数，例如

Length<void>::value为1;

Length<void,int,int>::value为3.