Placement New實現自More Effective C++ Item4

#include <iostream>

using namespace std;
class EquipmentPiece
{
public:
    EquipmentPiece(int IDNumber)
    {
        this->IDNumber = IDNumber;
    }
    void PrintOut()
    {
        cout << IDNumber << endl;
    }
private:
    int IDNumber;
};

int main()
{
    // 爲大小爲 10 的數組 分配足夠的內存
    // EquipmentPiece 對象;
    // operator new[] 函數
    char *rawMemory = new char[10*sizeof(EquipmentPiece)];
    // 或者void *rawMemory = operator new[](10*sizeof(EquipmentPiece));
    //  EquipmentPiece *bestPieces = static_cast<EquipmentPiece*>(rawMemory);
    // make bestPieces point to it so it can be treated as an
    // EquipmentPiece array
    EquipmentPiece *bestPieces = reinterpret_cast<EquipmentPiece*>rawMemory;
    // construct the EquipmentPiece objects in the memory
    // 使用"placement new"
    for (int i = 0; i < 10; ++i)
        new (&bestPieces[i]) EquipmentPiece(i);
    for (int i = 0; i < 10; ++i)
        bestPieces[i].PrintOut();
    // 以與構造 bestPieces 對象相反的順序
    // 解構它。
    for (int i = 9; i >= 0; --i)
        bestPieces[i].~EquipmentPiece();
    // deallocate the raw memory
    delete[]rawMemory;
    return 0;
}

運行結果如圖：

轉存失敗重新上傳取消