在 C++ 中被覆盖后如何调用原始 function？

Question

I serialize most of my classes with two functions, read() and write(). What I would like to do is have the read/write() function of the base class called from the subclasses so that I don't have to repeat the serialization code multiple times.

For example:

class Base
{
public:
   base();
   virtual read(QDataStream&);
   virtual write(QDataStream&);
private:
   int a, b, c, d;
}

class Sub : public Base
{
public:
    Sub();
    read(QDataStream&);
    write(QDataStream&);
private:
    int e, f, g, h;
}

So in this example, i would like the code to read/write a,b,c,d to come from Base. Sub would then call Base::read(QDataStream&) and then add whatever attributes are unique to Sub. This way I don't have to repeat the serialization code for each subclass (and possibly forget to do so).

Answer 1

You can call base-class functions by prepending the function call with the base-class identifier, followed by the scope operator (::).

Like this:

class Base
{
public:
     virtual void Function();
}

class Foo : public Base
{
public:
     void Function();
     void DoSomething();
}

void Foo::DoSomething()
{
     Base::Function();   // Will call the base class' version of Function().
     Function();         // Will call Foo's version of Function().
}

EDIT: Note removed by request.

Answer 2

void Sub::read(QDataStream &stream)
{
    Base::read(stream);
    // do Sub stuff here
}

Answer 3

First off - your member functions don't have return types - not valid in C++, your compiler might complain about 'default int' behavior and let it pass, but you should give them return types (I'll use void as a placeholder).

You can scope resolve and use the parent class version when you're in a subclass:

void Sub::read(QDataStream& qds) {
    Base::read(qds);

    // do more stuff
}