先给结论:
(1)派生类中的基类子对象和子对象必须初始化,初始化在派生类的构造函数的初始化列表中,如果初始化列表中没有进行初始化,则调用缺省的构造函数进行初始化。
(2)派生类构造函数的调用顺序:
基类的构造函数
子对象类的构造函数
派生类的构造函数
例子
class point1 { public: point1(); point1(int i); virtual ~point1(); private: int x; }; point1::point1() { x=1; cout<<"point1's default constructor called!\n"; } point1::point1(int i) { x=i; cout<<"point1's constructor called!\n"; } point1::~point1() { } class point2 : public point1 { public: point2(); point2(int i,int j,int k); virtual ~point2(); point1 p; }; point2::point2() { cout<<"point2's defaule constructor called\n"; } point2::point2(int i,int j,int k) { cout<<"point2's constructor called\n"; } point2::~point2() { } //主函数 void main() { point2 pp; point2 pp1(1,2,3); }
运行结果
point1's default constructor called!// point1 p;调用了基类默认构造函数 point1's default constructor called!// point2's defaule constructor called point1's default constructor called!// point1 p;调用了基类默认构造函数 point1's default constructor called! point2's constructor called
如果函数
point2::point2(int i,int j,int k) { cout<<"point2's constructor called\n"; }
改为:
point2::point2(int i,int j,int k):p(j) { cout<<"point2's constructor called\n"; }
运行结果为:
point1's default constructor called! point1's default constructor called! point2's defaule constructor called point1's default constructor called! point1's constructor called! point2's constructor called
时间: 2024-10-22 06:59:26