构造函数一般写法

class Person {
	int m_age;
	int m_height;
public:
    Person() :Person(0, 0) {

    }
    Person(int age) :Person(age, 0) {

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

如果使用了默认参数,可以简写成一个构造函数

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

调用示例

int main() {
	Person person;
	Person person2(10);
	Person person3(20, 180);

	getchar();
	return 0;
}

如果函数声明和实现是分离的

默认参数只能写在函数的声明中

 Person(int age = 0, int height = 0);

初始化列表只能写在函数的实现中

Person::Person(int age, int height) :m_age(age), m_height(height) {

}

父类的构造函数

1.子类的构造函数默认会调用父类的无参构造函数

class Person {
    int m_age;
public:
    Person() {
        cout << "Person()" << endl;
    }
    Person(int age) :m_age(age) {
        cout << "Person(int age)" << endl;
    }
};

class Student : public Person {
    int m_score;
public:
    Student() {
        cout << "Student()" << endl;
    }
    Student(int age, int score) :m_score(score), Person(age) {
        cout << "Student(int age, int score)" << endl;
    }
};

2.如果子类的构造函数显式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

3.如果父类缺少无参构造函数，子类的构造函数必须显式调用父类的有参构造函数

class Person {
	int m_age;
public:
	Person(int age) :m_age(age) {
		cout << "Person(int age)" << endl;
	}
};

class Student : public Person {
	int m_score;
public:
	Student() :Person(0) {

	}
};

构造函数、析构函数顺序

构造函数和析构函数顺序相反

int main() {
	Student student;

	getchar();
	return 0;
}

初始化子类student构造函数调用顺序 Person() -> Student()

子类student析构函数调用顺序 ~Student()-> ~Person()