运算符＆lt;＆lt;和继承
我在C ++中有以下类：
class Event {
//...
friend ofstream& operator<<(ofstream& ofs, Event& e);
};
class SSHDFailureEvent: public Event {
//...
friend ofstream& operator<<(ofstream& ofs, SSHDFailureEvent& e);
};
Event *e = new SSHDFailureEvent();
ofstream ofs("file");
ofs << *e;
没有找到相关结果
已邀请:
4 个回复
细屠截殴些
。 您可以在基类中定义虚函数并将其重新定义为所有派生类，并仅将定义为，class Event { virtual ofstream& print(ofstream & ofs) = 0 ; //pure virtual friend ofstream& operator<<(ofstream& ofs, Event& e); }; //define only once - no definition for derived classes! ofstream& operator<<(ofstream& ofs, Event& e) { return e.print(ofs); //call the virtual function whose job is printing! }膏焦凑
class Event { //... friend ofstream& operator<<(ofstream& ofs, Event& e) { e.print(ofs); return ofs; } virtual void print(std::ofstream& ofs) { ofs << "Eventn"; } }; class SSHDFailureEvent: public Event { virtual void print(std::ofstream& ofs) { ofs << "SSHDFailureEventn"; } };闲窍
class Event { public: virtual ~Event(); virtual std::ostream& printTo( std::ostream& ) const /*= 0*/; // other public methods }; /*inline*/ std::ostream& operator<<(std::ostream& os, const Event& event) { return event.printTo(os); }成为一个公共非虚拟函数，调用受保护或私有虚拟函数，就像所有虚函数一样。车料
在基地和孩子们。 要么 - 尝试动态地将基类强制转换为它的子类。