Qt每天一例9.迷惑的子父类转换

Posted 2022-01-12 鱼酱2333

猜猜输出的打印是啥

#include <QCoreApplication>
#include <QtDebug>

class Father

public:
    Father()
        qDebug()<<"father make";
    ;
    ~ Father()
        qDebug()<<"father dead";
    ;

;
class Son : public Father

public:
    int  cake=666;
    Son():cake(23333)
        qDebug()<<"son make";
    ;

    ~ Son()
        qDebug()<<"son dead";
    ;
    void shout()
    
        qDebug()<<"son shout"<<cake;
    
;

int main(int argc, char *argv[])

    QCoreApplication a(argc, argv);
    Father *f = new Father;
    static_cast<Son*>(f)->shout();



    return a.exec();

90%你猜错了

father make
son shout -1414812752

为什么？
因为static_cast只是个类型转换，所以cake是个未初始化值。