初始化列表-构造函数互相调用-

初始化列表，用来初始化成员变量的

Person(int age,int height) :m_age(age), m_height(height) {}    //m_age = age    m_height = height

初始化列表，只能放到实现里面

struct Person { 
    int m_age;
    int m_height;
    Person(int age = 0, int height = 0);
};

Person::Person(int age, int height) :m_age(age), m_height(height) {}    //这个只能放实现

构造函数的互相调用

struct Person {
    int m_age;
    int m_height;

    Person () : Person(0, 0){     //调用有参的构造函数,只能放这里

    }

    Person(int age, int height) {
        m_age = age;
        m_height = height;
    }
};

子类的构造函数默认会调用父类的无参构造函数

struct Person {
    int m_age;

    Person () {    
        cout << "Person::Person()" << endl;
    }
};

struct student : Person {
    int m_no;

    Student() {
        cout << "Student::Student()" << endl;
    }
};

int main() {
    Student student;    //默认还会调用父类的 Person()函数
}

子类的构造函数显示地调用了父类的有参构造函数，就不会再去默认调用父类的无参构造函数

Student() : Person(10) { ...}    /调用父类的有参构造函数写冒号后面

构造与析构顺序

struct Student : Person {
    Student() {
        // call Person::Person  先调用父类的构造
        cout << "Student::Student()" << endl;
    }
    ~Student() {
        cout << "Student::~Student()" << endl;
        // call Person::~Person 后调用父类的析构
    }
};