C++11 特性了解

Kernel Panic 总结了 C++11 中的 5 个实用特性:自动类型推导、强类型枚举、Unique 指针、static_assert、Lambdas 表达式。


Auto Type Deduction 自动类型推导


auto 关键字让用户得以使用 C++ 内置的类型推导特性。


Unique 指针


Unique 指针是 C++11 版本的智能指针类。


一旦你用 unique_ptr 关键字定义了一个对象,那么下列事件只要发生一个,对象就会被销毁并释放内存:


  • unique_ptr 管理的对象被销毁。

  • unique_ptr 管理的对象通过赋值操作符指向另一个指针,或调用了reset()方法。

#include "stdafx.h"
#include "TestCpp11.h"
#include <memory>
#include <vector>
#include <iostream>

#define MAX_LOADSTRING 100

// Global Variables:
HINSTANCE hInst;        // current instance
TCHAR szTitle[MAX_LOADSTRING];     // The title bar text
TCHAR szWindowClass[MAX_LOADSTRING];   // the main window class name

// Forward declarations of functions included in this code module:
ATOM    MyRegisterClass(HINSTANCE hInstance);
BOOL    InitInstance(HINSTANCE, int);
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
INT_PTR CALLBACK About(HWND, UINT, WPARAM, LPARAM);

class A
{
public:
 A() :m_pStr(nullptr), m_num(0){ OutputDebugString(_T("A()\r\n")); };
 A(UINT num) :m_pStr(nullptr),m_num(num){ OutputDebugString(_T("A()\r\n")); };
 ~A(){ OutputDebugString(_T("~A()\r\n")); };
 UINT GetNum(){ return m_num; };
private:
 TCHAR* m_pStr;
 UINT m_num;
};

int APIENTRY _tWinMain(_In_ HINSTANCE hInstance,
                     _In_opt_ HINSTANCE hPrevInstance,
                     _In_ LPTSTR    lpCmdLine,
                     _In_ int       nCmdShow)
{
 UNREFERENCED_PARAMETER(hPrevInstance);
 UNREFERENCED_PARAMETER(lpCmdLine);

  // TODO: Place code here.
 MSG msg;
 HACCEL hAccelTable;

 // Initialize global strings
 LoadString(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
 LoadString(hInstance, IDC_TESTCPP11, szWindowClass, MAX_LOADSTRING);
 MyRegisterClass(hInstance);

 // Perform application initialization:
 if (!InitInstance (hInstance, SW_HIDE))
 {
  return FALSE;
 }

 hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_TESTCPP11));
 {
  std::unique_ptr<A> Smartptr(new A);
  if (Smartptr->GetNum() == 0)
  {
   OutputDebugString(_T("Smartptr->GetNum() == 0\r\n"));
  }
 }
 
 std::vector<A*> tVector;
 A* pA1 = new A;
 A* pA2 = new A(2);
 A* pA3 = new A(4);
 tVector.push_back(pA1);
 tVector.push_back(pA2);
 tVector.push_back(pA3);
 //std::vector<A*>::iterator aitertor;
 for (auto aitertor = tVector.begin(); aitertor != tVector.end(); aitertor++)
 {
  UINT i = (*aitertor)->GetNum();
  std::cout << i << std::endl;
 }

 // Main message loop:
 /*while (GetMessage(&msg, NULL, 0, 0))
 {
 if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
 {
 TranslateMessage(&msg);
 DispatchMessage(&msg);
 }
 }
 */
 return (int) 0;
}



//
//  FUNCTION: MyRegisterClass()
//
//  PURPOSE: Registers the window class.
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
 WNDCLASSEX wcex;

 wcex.cbSize = sizeof(WNDCLASSEX);

 wcex.style   = CS_HREDRAW | CS_VREDRAW;
 wcex.lpfnWndProc = WndProc;
 wcex.cbClsExtra  = 0;
 wcex.cbWndExtra  = 0;
 wcex.hInstance  = hInstance;
 wcex.hIcon   = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_TESTCPP11));
 wcex.hCursor  = LoadCursor(NULL, IDC_ARROW);
 wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
 wcex.lpszMenuName = MAKEINTRESOURCE(IDC_TESTCPP11);
 wcex.lpszClassName = szWindowClass;
 wcex.hIconSm  = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));

 return RegisterClassEx(&wcex);
}

//
//   FUNCTION: InitInstance(HINSTANCE, int)
//
//   PURPOSE: Saves instance handle and creates main window
//
//   COMMENTS:
//
//        In this function, we save the instance handle in a global variable and
//        create and display the main program window.
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
   HWND hWnd;

   hInst = hInstance; // Store instance handle in our global variable

   hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);

   if (!hWnd)
   {
      return FALSE;
   }

   ShowWindow(hWnd, nCmdShow);
   UpdateWindow(hWnd);

   return TRUE;
}

//
//  FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM)
//
//  PURPOSE:  Processes messages for the main window.
//
//  WM_COMMAND - process the application menu
//  WM_PAINT - Paint the main window
//  WM_DESTROY - post a quit message and return
//
//
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
 int wmId, wmEvent;
 PAINTSTRUCT ps;
 HDC hdc;

 switch (message)
 {
 case WM_COMMAND:
  wmId    = LOWORD(wParam);
  wmEvent = HIWORD(wParam);
  // Parse the menu selections:
  switch (wmId)
  {
  case IDM_ABOUT:
   DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
   break;
  case IDM_EXIT:
   DestroyWindow(hWnd);
   break;
  default:
   return DefWindowProc(hWnd, message, wParam, lParam);
  }
  break;
 case WM_PAINT:
  hdc = BeginPaint(hWnd, &ps);
  // TODO: Add any drawing code here...
  EndPaint(hWnd, &ps);
  break;
 case WM_DESTROY:
  PostQuitMessage(0);
  break;
 default:
  return DefWindowProc(hWnd, message, wParam, lParam);
 }
 return 0;
}

// Message handler for about box.
INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
 UNREFERENCED_PARAMETER(lParam);
 switch (message)
 {
 case WM_INITDIALOG:
  return (INT_PTR)TRUE;

 case WM_COMMAND:
  if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
  {
   EndDialog(hDlg, LOWORD(wParam));
   return (INT_PTR)TRUE;
  }
  break;
 }
 return (INT_PTR)FALSE;
}


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