C++数据结构继承的概念与菱形继承及虚拟继承和组合

class Person
{
public:
	Person(const char* name = "")
		:_name(name)
	{}
	void Print()
	{
		cout << "name:" << _name << " age:" << _age << endl;
	}
protected:
	string _name = "";
	int _age = 1;
};
class Student : public Person
{
public:
	Student()
		:Person("xiaoming")
	{}
	void Print()
	{
		cout << "name:" << _name << " age:" << _age << " _stuid:" << _stuid << " _major:" << _major << endl;
	}
private:
	int _stuid = 0;// 学号
	int _major = 0;// 专业
};
int main()
{
	Student s;
	// 子类对象可以赋值给父类的对象、指针和引用  反过来不行
	// Student对象通过 “切片” 或 “切割” 的方式进行赋值
	Person p1 = s;
	Person* p2 = &s;
	Person& p3 = s;

	p1.Print();
	p2->Print();
	p3.Print();

	// 基类的指针可以通过强制类型转换赋值给派生类的指针
	Student* ps = (Student*)p2;

	ps->Print();

	return 0;
}

class Person
{
public:
	Person(const char* name = "")
		:_name(name)
	{}
	void Print()
	{
		cout << "name:" << _name << " age:" << _age << endl;
	}
protected:
	string _name = "";
	int _age = 1;
};
class Teacher : public Person
{
public:
	void Print()
	{
		cout << "name:" << _name << " age:" << _age << " jobid:" << _jobid << endl;
	}
private:
	int _jobid = 0;// 工号
};
int main()
{
	Teacher t;

	t.Print();
	t.Person::Print();// 子类会隐藏（重定义）父类的同名成员（同名函数或同名成员变量） 可以通过指定域作用限定符访问

	return 0;
}

class A
{
public:
	void fun()
	{
		cout << "func()" << endl;
	}
};
class B : public A
{
public:
	void fun(int i) 
	{
		A::fun();
		cout << "func(int i)->" << i << endl;
	}
};
void Test()
{
	B b;
	b.fun(10);
};

class Person
{
public:
	Person(const char* name = "", int age = 1)
		:_name(name)
		,_age(age)
	{
		cout << "Person()" << endl;
	}
	Person(const Person& p)
		:_name(p._name)
		, _age(p._age)
	{
		cout << "Person(const Person& p)" << endl;
	}
	Person& operator=(const Person& p)
	{
		_name = p._name;
		_age = p._age;
		cout << "Person& operator=(const Person& p)" << endl;
		return *this;
	}
	void Print()
	{
		cout << "name:" << _name << " age:" << _age << endl;
	}
	~Person()
	{
		cout << "~Person()" << endl;
	}
protected:
	string _name;
	int _age;
};


class Student : public Person
{
public:
	Student(const char* name, int age, int stuid = 0)
		:Person(name, age)// 此处调用父类的构造函数堆继承下来的成员进行初始化，不谢的话，编译器调用父类的默认构造函数
		, _stuid(stuid)
	{
		cout << "Student()" << endl;
	}
	Student(const Student& s)
		:Person(s)// 子类对象可以传给父类的对象、指针或引用
		,_stuid(s._stuid)
	{
		cout << "Student(const Student& s)" << endl;
	}
	Student& operator=(const Student& s)
	{
		cout << "Student& operator=(const Student& s)" << endl;
		if (this != &s)
		{
			Person::operator=(s);// 先完成基类的复制
			_stuid = s._stuid;
		}

		return *this;
	}
	void Print()
	{
		cout << "name:" << _name << " age:" << _age << " _stuid:" << _stuid << endl;
	}
	~Student()
	{
		// 基类和派生类的析构函数的函数名都被编译器处理成了destruction，构成隐藏，是一样指定域访问
		//Person::~Person();// 不需要显示调用 编译器会自动先调用派生类的析构函数，然后调用基类的析构函数
		cout << "~Student()" << endl;
	}
private:
	int _stuid;// 学号
};

void test1()
{
	Student s("小明",18,10);
}

void test2()
{
	Student s1("小明", 18, 10);
	Student s2(s1);
}

class Person
{
public:
	Person()
	{
		++_count;
	}
	// static成员存在于整个类  无论实例化出多少对象，都只有一个static成员实例
	static int _count;
};

int Person::_count = 0;

class Student :public Person
{
public:
	int _stuid;
};

int main()
{
	Student s1;
	Student s2;
	Student s3;

	// Student()._count = 10;
	cout << "人数：" << Student()._count - 1 << endl;

	return 0;
}

class Person
{
public:
	string _name;
};
// 不要在其他地方去使用。
class Student : virtual public Person
{
public:
	int _num; //学号
};
class Teacher : virtual public Person
{
public:
	int _id; // 职工编号
};
class Assistant : public Student, public Teacher
{
protected:
	string _majorCourse; // 主修课程
};

class A
{
public:
	int _a;
};

class B :virtual public A
{
public:
	int _b;
};

class C :virtual public A
{
public:
	int _c;
};

class D : public B, public C
{
public:
	int _d;
};
int main()
{
	D d;
	d.B::_a = 1;
	d.C::_a = 2;
	d._b = 4;
	d._c = 5;
	d._d = 6;

	return 0;
}