动态变量不起作用

Question

in this code why does the first("invNummer") is always 0, when I initializate it dynamically? When I do it as a static(two) it works.

class Computer {
private:
    int invNummer;
    char* osName;
    int state; // 0 – aus, 1 - an
public:
    Computer(int INV, char* OS, int st);

    void info() {
        cout << invNummer << " " << osName << " " << state << endl;
    }
};

Computer::Computer(int INV, char* OS, int st)
    : invNummer(INV)
    , osName(OS)
    , state(st)
{};

int main()
{
    Computer* one;
    one = new Computer(10, (char*)"Windows", 1);
    delete one;
    Computer two(9, (char*)"Linux", 0);

    one->info();
    two.info();

    return 0;
}

Output looks like this:

0 Windows 1
9 Linux 0

Answer 1

As @It's_comming_home pointed out to you, your issue is not related to creating the one object dynamically, but to the deletion of that object:

delete one;

When you delete the one object, the pointer is left dangling, ie it is no longer usable. If you try to dereference it afterwards:

one->info();

You will get undefined behavior , like your output shows.

To fix this, just move the deletion of the one object after you invoke its info() method:

one->info();
two.info();

delete one;