由于笔者的水平不太行，在这个贴里记录一些自己犯过的不太容易被发现的错误
20221029
基类
class CBase
{
public:
virtual ~CBase() {}
private:
virtual bool __fooV() { return true; }
friend class CFactory;
};
继承类
class CDerived : public CBase
{
private:
virtual bool __fooV(int x) { return x > 100; }
friend class CFactory;
};
工厂类
class CFactory
{
public:
template <typename TDerived, class... TArgs>
requires std::is_base_of<CBase, TDerived>::value
static TDerived* createResource(TArgs&&... vArgs)
{
TDerived* pDerived = new TDerived();
assert(pDerived);
CBase* pBase = pDerived;
bool IsInitSucceed;
if (sizeof...(vArgs) > 0) IsInitSucceed = pDerived->__fooV(std::forward<TArgs>(vArgs)...);
else IsInitSucceed = pBase->__fooV();
if (!IsInitSucceed)
{
delete pDerived;
pDerived = nullptr;
}
return pDerived;
}
};
CDerived* pDerived = CFactory::createResource<CDerived>();
期望：在函数 CFactory::createResource 的实例化中，由于模板参数包的大小为0，所以最后当然会执行else分支的部分，那么不管if部分的话，编译肯定是能顺利通过的吧？
事实：编译的时候可不会管哪些函数会不会被执行到，CBase::__fooV 对 CDerived 不可见，自然编译就失败了。
修改方法：在 CDerived 中override __fooV()
标签：__,pDerived,c++,class,CFactory,CBase,有趣,fooV From： https://www.cnblogs.com/hinanawitenshi/p/16840364.html