派生 class 上的 C++ 赋值运算符实现

Question

假设我有一个基础 class，它看起来像这样：

class Base
{
public:
   Base(){ baseMember = new int( 10 ); }

   Base &operator=( const Base &right )
   {
      baseMember = new int( *(right.baseMember) );
      return *this;
   }
protected:
   int *baseMember;
};

现在我想要一个继承自 Base 的 Derived class，并有一个名为 derivedMember 的新指针成员：

class Derived : public Base
{
public:
   Derived():Base(){ derivedMember = new double( 10.1 ); }

   Derived &operator=( const Derived &right )
   { /*some implementation */ }
private:
   double *derivedMember;
};

我应该如何在 Derived class 上执行 operator= 实现，这样我就可以调用 base class operator= 并避免重写 Base class operator = 在 Derived class 上实现？简单来说，我怎样才能避免这样做：

Derived &operator=(const Derived &right )
{
   baseMember = new int( *(right.baseMember) ); //this is what I want to avoid rewriting
   derivedMember = new double( *(right.derivedMember) );
   return *this;
}

Answer 1

像这样：

Derived &operator=(const Derived &right )
{
    if (&right == this) { return *this; } // prevent assigning to self
    Base::operator=(right);
    delete derivedMember; // remember to release any assigned memory (assumes derivedMember is assigned a default of nullPtr)
    derivedMember = new double( *(right.derivedMember) );
    return *this;
}

派生 class 上的 C++ 赋值运算符实现

C++ assignment operator implementation on derived class

c++

inheritance

operator-overloading