标签:类型转换 std 转换 cout 派生类 C++ basePtr 基类 指针
#include <iostream>
#include <memory>
struct Base
{
int a;
virtual void f() const { std::cout << "I am base!\n";}
virtual ~Base(){}
};
struct Derived : Base
{
void d()
{ std::cout << "Derived:d()\n"; }
void f() const override
{ std::cout << "I am derived!\n"; }
~Derived(){}
};
int main(){
auto basePtr = std::make_shared<Base>();
std::cout << "Base pointer says: ";
basePtr->f();
auto derivedPtr = std::make_shared<Derived>();
std::cout << "Derived pointer says: ";
derivedPtr->f();
// 上行的转换(派生类到基类的转换)
std::cout << "Derived pointer static_pointer_cast to Base says: ";
std::static_pointer_cast<Base>(derivedPtr)->f();
// 直接转型,不构造临时 shared_ptr
// 下行的转换(基类到派生类的转换)
std::cout << "Base pointer static_cast to derived says: ";
static_cast<Derived*>(basePtr.get())->d();
// 构造临时 shared_ptr ,然后调用 operator->
// 下行的转换(基类到派生类的转换)
std::cout << "Base pointer static_pointer_cast to derived says: ";
std::static_pointer_cast<Derived>(basePtr)->d();
// 转换成对象
// 下行的转换(基类到派生类的转换)
Derived& derived = static_cast<Derived&>(*basePtr);
std::cout << "Base pointer static_cast to derived Obeject says: ";
derived.d();
// std::cout << "Base pointer dynamic_cast to derived says: ";
// dynamic_cast<Derived*>(basePtr.get())->f(); //段错误
// Derived& derived1 = dynamic_cast<Derived&>(*basePtr);
// derived1.d(); // 异常
// 下行的转换(基类到派生类的转换)
auto downcastedPtr = std::dynamic_pointer_cast<Derived>(basePtr);
if(downcastedPtr)
{
std::cout << "Base pointer dynamic_pointer_cast to derived says: ";
downcastedPtr->d();
}
// All pointers to derived share ownership
std::cout << "Pointers to underlying derived: "
<< derivedPtr.use_count()
<< "\n";
}
标签:类型转换,std,转换,cout,派生类,C++,basePtr,基类,指针 来源: https://www.cnblogs.com/codebai/p/16224295.html
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