12.2 Derived Classes

派生类

• Inherit members (attributes and functions) from one class
  • Base class (parent)
  • Derived class (child)
• C++ supports multiple inheritance and multilevel inheritance

子类可以得到父类的成员

class Base
{
  public:
    int a;
    int b;
};
class Derived: public Base
{
  public:
    int c;
};
class Derived: public Base1, public Base2
{
    ...
};

Constructors

• To instantiate a derived class object
  • Allocate memory
  • Derived constructor is invoked
    • Base object is constructed by a base constructor
    • Member initializer list initializes members
    • To execute the body of the derived constructor ```cpp class Derived: public Base { public: int c; Derived(int c): Base(c - 2, c - 1), c(c) { … } };

``` Destructors

• The destructor of the derived class is invoked first, 子类的析构函数先执行
• Then the destructor of the base class.