C++语法游戏 ： 模仿C#的 using(...){}

游戏而已，，可以用来锻炼脑筋。。~~ //using.h #pragma once //for IUnknown #include "atlbase.h" #define USING_SCOPE_ASSERT(x) ATLASSERT(x); #define USING_SCOPE_INLINE inline #define Using(expression) if(UsingScope UsingScope_LocalVar=(expression)) class UsingScope { class Container { public: virtual ~Container() { } }; Container* pc; public: USING_SCOPE_INLINE operator bool () { return true; } USING_SCOPE_INLINE ~UsingScope() { delete pc; } template class SimplePointerContainer:public Container { T* p; public: SimplePointerContainer(T* p) { USING_SCOPE_ASSERT(p!=NULL); this->p=p; } virtual ~SimplePointerContainer() { delete p; } }; template USING_SCOPE_INLINE UsingScope(T* p) { pc=new SimplePointerContainer(p); } class IUnknownContainer:public Container { IUnknown* punk; public: IUnknownContainer(IUnknown* punk) { USING_SCOPE_ASSERT(punk!=NULL); this->punk=punk; } virtual ~IUnknownContainer() { punk->Release(); } }; USING_SCOPE_INLINE UsingScope(IUnknown* punk) { pc=new IUnknownContainer(punk); } class BSTRContainer:public Container { BSTR bstr; public: BSTRContainer(BSTR bstr) { USING_SCOPE_ASSERT(bstr!=NULL); this->bstr=bstr; } virtual ~BSTRContainer() { SysFreeString(bstr); } }; USING_SCOPE_INLINE UsingScope(BSTR bstr) { pc=new BSTRContainer(bstr); } //vc7 m 可以为System::IDisposable* 添加 .Dispose() 的调用 //以支持所有的do.net System::IDisposable的实现者 }; //usingT.h #include "Using.h" #define UsingT(type,varname,expression) if(UsingScopeT varname=(expression)) template class UsingScopeT { template class Container { public: T* p; Container(T* p) { USING_SCOPE_ASSERT(p!=NULL); this->p=p; } virtual ~Container(){} }; Container* pc; public: USING_SCOPE_INLINE operator bool () { return true; } USING_SCOPE_INLINE T* operator -> () { return (pc->p); } USING_SCOPE_INLINE operator T*() const { return (T*)(pc->p); } USING_SCOPE_INLINE T& operator*() const { return *(pc->p); } USING_SCOPE_INLINE T** operator&() { return &(pc->p); } USING_SCOPE_INLINE bool operator==(T* pT) const { return (pc->p) == pT; } USING_SCOPE_INLINE ~UsingScopeT() { delete pc; } template class SimplePointerContainer:public Container { public: SimplePointerContainer(T* p):Container(p) { } virtual ~SimplePointerContainer() { delete p; } }; template USING_SCOPE_INLINE UsingScopeT(T* p) { pc=new SimplePointerContainer(p); } class IUnknownContainer:public Container { public: IUnknownContainer(IUnknown* punk):Container(punk) { } virtual ~IUnknownContainer() { p->Release(); } }; USING_SCOPE_INLINE UsingScopeT(IUnknown* punk) { pc=new IUnknownContainer(punk); } class BSTRContainer:public Container { public: BSTRContainer(BSTR bstr):Container(bstr) { } virtual ~BSTRContainer() { SysFreeString(p); } }; USING_SCOPE_INLINE UsingScopeT(BSTR bstr) { pc=new BSTRContainer(bstr); } //vc7 m 可以为System::IDisposable* 添加 .Dispose() 的调用 //以支持所有的dotnet System::IDisposable的实现者 }; //Using.Cpp // Using.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include "atlbase.h" #include "Using.h" #include "UsingT.h" class ClassA { public: ClassA() { _tprintf(_T("ClassA()\n")); } virtual ~ClassA() { _tprintf(_T("~ClassA()\n")); } virtual void Write() { _tprintf(_T("ClassA::Write\n")); } }; class ClassB:public ClassA { public: virtual void Write() { _tprintf(_T("ClassB::Write\n")); } }; ClassA* CreateClassA() { return new ClassB(); } IUnknown* ReturnUnknown() { HRESULT hres; IUnknown* p; CLSID cid; hres=CLSIDFromProgID(L"JScript",&cid); hres=CoGetClassObject(cid,CLSCTX_INPROC_SERVER,NULL,IID_IClassFactory,(void**)&p); return p; } void DoIt() { CoInitialize(NULL); IUnknown* punk; Using(punk=ReturnUnknown()) { ClassA* pa; Using(pa=CreateClassA()) { _tprintf(_T("DoWork\n")); pa->Write(); } } UsingT(ClassB,pb,new ClassB()) { pb->Write(); ClassA* pa=pb; if(pa==pb) pa->Write(); } UsingT(IUnknown,p,ReturnUnknown()) { //p->.. } CoUninitialize(); } int main(int argc, char* argv[]) { DoIt(); return 0; }

原文转自：http://www.ltesting.net