1、std::static_pointer_cast():当指针是智能指针时候,向上转换,用static_cast 则转换不了,此时需要使用static_pointer_cast。 2、std::dynamic_pointer_cast():当指针是智能指针时候,向下转换,用dynamic_cast 则转换不了,此时需要使用dynamic_pointer_cast(此处注意:base基类需要至少有一个virtual成员函数(即多态类...
std::shared_ptr<T>(dynamic_cast<T*>(r.get())以及std::shared_ptr<T>(const_cast<T*>(r.get()))似乎(might seem)有相同的效果,但是这些表达式会造成程序产生未定义行为,未定义行为就是可能会尝试销毁删除同一个对象多次
dynamic_pointer_cast不是语言关键字,在标准库<memory>中定义,位于std命名空间中,专用于智能指针shared_ptr的转换。可以理解为智能指针领域的dynamic_cast操作符。 总结一下:它们的基本区别,就是dynamci_cast用于裸指针和引用等动态类型的转型,而dynamic_pointer_cast主要用于智能指针的转型。 例子: //注意:dynamic_po...
I defined a structure, like the one below that stored pointers already cast to the types I wanted. I then populated the struct (setting the ones that were not supported by the "real" object to null),having allocated it on the heap and then just casted a double to return to my script,...
Can I just say, please don't cast the return value of malloc? It is not required and can hide errors. I agree that the cast is not required in C. It is mandatory in C++, so I usually add them just in case I have to port the code in C++ one day. However, I wonder how cast...
例如基类Father ,Son继承Father,派生类Son.。Father—>Son则为向下转换,Son—>Father则为向上转换。向上转换为隐士转换,向下转换需要dynamic_cast或者c的转换方式。 向上转换: struct Father { //基类Father }; struct Son:Father { //基类Father的派生类B ...
This is fine and is a fairly common technique for implementing "object-orientation" in C. Because the memory layout ofstructs is well-defined in C, as long as the two object share the same layout then you can safely cast pointers between them. That is, the offset of thetypemember is th...
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spDeriveDown = dynamic_pointer_cast<CDerive>(spBaseDown); if (spDeriveDown == NULL) //由于会进行类型的检查,这边是返回NULL cout << "spDeriveDown is null" << endl; /* shared_ptr<CDerive> spDeriveDown; shared_ptr<CBase> spBaseDown; ...
spDeriveDown= dynamic_pointer_cast<CDerive>(spBaseDown);if(spDeriveDown == NULL)//由于会进行类型的检查,这边是返回NULLcout <<"spDeriveDown is null"<<endl;/*shared_ptr<CDerive> spDeriveDown; shared_ptr<CBase> spBaseDown; spBaseDown = make_shared<CDerive>(); ...