C++標(biāo)準(zhǔn)轉(zhuǎn)換運(yùn)算符dynamic

1、c+標(biāo)準(zhǔn)轉(zhuǎn)換運(yùn)算符dynamicdynamic_cast new_type (pression) dynamic_cast運(yùn)算符，應(yīng)當(dāng)算是四個(gè)里面最特別的一個(gè)，由于它涉及到編譯器的屬性設(shè)置，而且牽扯到的面對(duì)對(duì)象的多態(tài)性跟程序運(yùn)行時(shí)的狀態(tài)也有關(guān)系，所以不能徹低的用法傳統(tǒng)的轉(zhuǎn)換方式來(lái)替代。但是也因此它是最常用，最不行缺少的一個(gè)運(yùn)算符。 與ic_cast一樣，dynamic_cast的轉(zhuǎn)換也需要目標(biāo)類型和源對(duì)象有一定的關(guān)系：繼承關(guān)系。 更精確的說(shuō)，dynamic_cast是用來(lái)檢查兩者是否有繼承關(guān)系。因此該運(yùn)算符事實(shí)上只接受基于類對(duì)象的指針和引用的類轉(zhuǎn)換。從這個(gè)方面來(lái)看，似乎dynamic_cast

2、又和reinterpret_cast是全都的，但事實(shí)上，它們還是存在著很大的差別。 還是用代碼來(lái)說(shuō)明，讓編譯器來(lái)解釋吧。 / / cast_operator_comparison.p / language: c+ / complier: vial studio 2010, xcode3.2.6 / platfo: macbook pro 2010 / appliion: none / author: ider, syracuse university er.cs / ilude sing include iostream using namespace std; class parents p

3、ublic: parents(string n=parent) name = n; virtual parents() virtual void speak() cout ti am name , i love my children. endl; void work() cout ti am name , i ne to work for my family. endl; protected: string name; class children : public parents public: children(string n=child):parents(n) virtual chi

4、ldren() virtual void speak() cout ti am name , i love my parents. endl; *children inherit work() method from parents, *it could be treated like part- job. void study() cout ti am name , i need to study for future. endl; private: /string name; /inherit name member from parents class stranger public:

5、stranger(string n=stranger)name = n; virtual stranger() void self_introce() cout ti am a stranger endl; void speak() /cout i am a stranger endl; cout tdo not talk to name , is a stranger. endl; private: string name; int main() /* cast from child class to base class */ cout dynamic_cast from child cl

6、ass to base class: endl; children * daughter_d = new children(daughter who pretend to be my mother); parents * mother_d = dynamic_cast parents* (daughter_d); /right, cast with polymorphism mother_d- speak(); mother_d- work(); /mother_d- study(); /error, no such method cout static_cast from child cla

7、ss to base class: endl; children * son_s = new children(son who pretend to be my father); parents * father_s = static_cast parents* (son_s); /right, cast with polymorphism father_s- speak(); father_s- work(); /father_s- study(); /error, no such method cout endl; /* cast from base class to child clas

8、s */ cout dynamic_cast from base class to child class: endl; parents * father_d = new parents(father who pretend to be a my son); children * son_d = dynamic_cast children* (father_d); /no error, but not safe if (son_d) son_d- speak(); son_d- study(); ee cout tnull endl; cout static_cast from base cl

9、ass to child class: endl; parents * mother_s = new parents(mother who pretend to be a my daugher); children * daughter_s = static_cast children* (mother_s); /no error, but not safe if (daughter_s) daughter_s- speak(); daughter_s- study(); else cout tnull endl; cout endl; /* cast between non-related

10、class */ cout dynamic_cast to non-related class: endl; stranger* stranger_d = dynamic_cast stranger* (daughter_d); if (stranger_d) stranger_d- self_introduce(); stranger_d- speak(); else cout tnull endl; /stranger* stranger_s = static_cast stranger* (son_s); /error, invalid cast cout reinterpret_cast to non-related class: endl; stranger* stranger_r = reinterpret_cast stranger* (son_s); if (stranger_r) stranger_d- self_introduce();