若r为空,则新的shared_ptr亦然(但其存储指针不必为空)。否则,新的shared_ptr将与r的初始值共享所有权,但若dynamic_pointer_cast所进行的dynamic_cast返回空指针,则它为空。 令Y为typenamestd::shared_ptr<T>::element_type,则将分别通过求值下列表达式,获得所得std::shared_ptr的存储指针: ...
(Derived*d=dynamic_cast<Derived*>(b1);d!=nullptr){std::cout<<"成功从 b1 向下转换到 d\n";d->name();// 可以安全调用}Base*b2=new Derived;if(Derived*d=dynamic_cast<Derived*>(b2);d!=nullptr){std::cout<<"成功从 b2 向下转换到 d\n";d->name();// 可以安全调用}delete b1;delete...
template <class Ty, class Other> shared_ptr<Ty> dynamic_pointer_cast(const shared_ptr<Other>& sp); ParametersTy The type controlled by the returned shared pointer. Other The type controlled by the argument shared pointer. sp The argument shared pointer.Remarks...
std::dynamic_pointer_cast的别名在C++标准库中是否存在? std::dynamic_pointer_cast的别名是否可以提高代码的可读性? c++中的std::stod, stCPP程序说明std::stod():stof, std::stold amp; str, std::size_t* pos = 0 ); Return Value: 返回double类型的值 参数 str : 要转换的字符串 pos : 存储处...
Depending on the type of the referenced object, a write operation through the resulting pointer, reference, or pointer to data member might produce undefined behavior. const_cast仅在其位于的那句语句中生效,下一条语句后,原const对象还是const属性。The cast lasts only for the remainder of the ...
std::shared_ptr<T> static_pointer_cast( const std::shared_ptr<U>& r ) noexcept; (1) (C++11 起) template< class T, class U >std::shared_ptr<T> static_pointer_cast( std::shared_ptr<U>&& r ) noexcept; (2) (C++20 起) template< class T, class U >std::shared_ptr<T> ...
5253//sidecast for pointer54if(A* a = dynamic_cast<A*>(baseB1))55{56a->f();57}58else59{60std::cout <<"Not the right A type!"<<std::endl;61}62std::cout <<"---"<<std::endl;6364//sidecast for reference65try{66A& a = dynamic_cast<A&>(baseB2);67a.f();68}catch(con...
具体的资料是在http://en.cppreference.com/w/cpp/language/dynamic_cast看到的。 If the casted type is a pointer, the pointed object is checked whether it is the requested base class. If the check succeeds, pointer to the requested base class is returned, otherwiseNULLpointer is returned. ...
int* pi = reinterpret_cast<int*>(pf);简而言之,static_cast<> 将尝试转换,举例来说,如float-到-integer,而reinterpret_cast<>简单改变编译器的意图重新考虑那个对象作为另一类型。 指针类型(Pointer Types) 指针转换有点复杂,我们将在本文的剩余部分使用下面的类: ...
TAnd<TIsPointer<To>, TAnd<TIsCastableToPointer<typename TRemovePointer<To>::Type>, TIsCastable<From>>>::Value, To>::Type DynamicCast(From* Arg) { return dynamic_cast<To>(Arg); } 第三个版本: 在原生cpp中的dynamic_cast除了可以指针之间转换还可以引用之间转换 en.cppreference.com/w/cSafely...