Scott Meyes 是世界頂尖C++大師，著作有《Effective C++》，《More Effective C++》等，並發表許多著名評論和文章。
關鍵字：traits, partial specialization, 指向成員函數的指針, operator->*
DarkSpy 2002/4/24
/*NOTE
請使用g++ 2.97 or higher,
Intel C++ 5.0 or higher (6.0 beta for DarkSpy only [DarkSpy report bug])
編譯，其他主流編譯器無法正確通過, VC 居然出現 26 處錯誤 */
#include
#include // 包含 pair 和 make_pair
using namespace std;
template
strUCt MemFuncTraits { };
//partial specialization 1
template
struct MemFuncTraits {
typedef R ReturnType;
typedef O ObjectType;
};
//partial specialization 2
template
struct MemFuncTraits {
typedef R ReturnType;
typedef O ObjectType;
};
//partial specialization 3
template
struct MemFuncTraits {
typedef R ReturnType;
typedef O ObjectType;
};
//partial specialization 4
template
struct MemFuncTraits {
typedef R ReturnType;
typedef O ObjectType;
};
template
class PMFC {
public:
typedef typename MemFuncTraits ::ObjectType ObjectType;
typedef typename MemFuncTraits ::ReturnType ReturnType;
typedef std::pair CallInfo;
PMFC(const CallInfo& info) : _callinfo(info) { } //init
// 支持無參數類型，ReturnType = MemFuncPreType
ReturnType operator()() const
{ return (_callinfo.first->*_callinfo.second)(); }
// 支持具有參數類型
template
ReturnType operator()(Param1Type p1) const
{ return (_callinfo.first->*_callinfo.second)(p1); }
private:
CallInfo _callinfo;
};
template
class SmartPtrBase {
public:
SmartPtrBase(T *p) : ptr(p) { } //init
//partial specialization PMFC 並 重載 operator->*.
template
const PMFC operator->*(MemFuncPtrType pmf) const
{ return std::make_pair(ptr, pmf); }
private:
T* ptr;
};
template
class SP : private SmartPtrBase {
// g++ 3.0.2 都有錯誤，改為 public，估計是一個 bug。Intel C++沒有錯誤。
public:
SP(T *p) : SmartPtrBase (p) { }
using SmartPtrBase ::operator->*;
//強制將 private 繼承的 operator->* 繼承為 public 為 main 中調用。
};
class Wombat {
public:
int dig() { cout << "Digging..." << endl; return 1; }
int sleep() { cout << "Sleeping..." << endl; return 5; }
int eat() const { cout << "Eatting..." << endl; return 7; }
int move(int op) { cout << "Moving..." << endl; return 9; }
};
typedef int (Wombat::*PWMF)(); //for Wombat::dig(0, sleep()
typedef int (Wombat::*PWMFC)() const; //for Wombat::eat() const
typedef int (Wombat::*PWMF1)(int); //for Wombat::move()
main()
{
SP pw = new Wombat;
PWMF pmf = &Wombat::dig;
(pw->*pmf)(); // Digging...
pmf = &Wombat::sleep;
(pw->*pmf)(); // Sleeping...
PWMFC pmfc = &Wombat::eat;
(pw->*pmfc)(); // Eatting...
PWMF1 pmf1 = &Wombat::move;
(pw->*pmf1)(2); // Eatting...
return 0;
}
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