1. Single inheritance
As the name implies, a subclass inherits only one class. Of course, unlike Java, a subclass can inherit multiple parent classes.
#include "stdafx.h"
#include "iostream.h"
#include "string.h"
#define MAXLEN 128 //定义一个宏
class CEmployee //定义员工类
{
protected: //定义protected数据成员
int m_nID; //定义员工ID
char m_szName[MAXLEN]; //定义员工姓名
char m_szDepart[MAXLEN]; //定义所属部门
public:
CEmployee() //定义默认构造函数
{
memset(m_szName, 0, MAXLEN); //初始化m_szName
memset(m_szDepart, 0, MAXLEN); //初始化m_szDepart
cout << "Employee构造函数被调用" << endl;
}
void SetName(const char* pszName) //设置员工姓名
{
strcpy(m_szName, pszName);
}
char* GetName()const //获取员工姓名
{
return (char*) m_szName;
}
void SetDepart(const char* pszDepart) //设置部门信息
{
strcpy(m_szDepart, pszDepart);
}
char* GetDepart()const //获取部门信息
{
return (char*) m_szDepart;
}
void OutputName() //输出员工姓名
{
cout << "员工姓名: " << m_szName << endl;
}
};
class COperator :public CEmployee //定义一个操作员类，从CEmployee类派生而来
{
private:
char m_szPassword[MAXLEN]; //定义密码
public:
COperator() //构造函数
{
memset(m_szPassword, 0, MAXLEN);
cout << "Operator构造函数被调用!" << endl;
}
void SetPassword(const char* pszPassword) //设置密码
{
strcpy(m_szPassword, pszPassword);
}
char* GetPassword()const //获取密码
{
return (char*) m_szPassword;
}
bool Login() //定义登录方法
{
if (strcmp(m_szName, "MR")==0 //比较用户名
&& strcmp(m_szPassword, "KJ")==0) //比较密码
{
cout << "登录成功!" << endl; //输出信息
return true; //设置返回值
}
else
{
cout << "登录失败!" << endl; //输出信息
return false; //设置返回值
}
}
};
int main(int argc, char* argv[])
{
COperator Operator; //定义一个COperator对象
Operator.SetName("MR"); //调用基类的SetName方法
Operator.SetPassword("KJ"); //调用SetPassword方法
Operator.Login(); //调用Login方法
return 0;
}2. Virtual function
A member function modified with the virtual keyword is a virtual function, and c# also uses this keyword.
// VirtualFunction.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include "iostream.h"
#include "string.h"
#define MAXLEN 128 //定义一个宏
class CEmployee //定义员工类
{
protected:
int m_nID; //定义员工ID
char m_szName[MAXLEN]; //定义员工姓名
char m_szDepart[MAXLEN]; //定义所属部门
public:
CEmployee() //定义默认构造函数
{
memset(m_szName, 0, MAXLEN); //初始化m_szName
memset(m_szDepart, 0, MAXLEN); //初始化m_szDepart
cout << "Employee构造函数被调用" << endl;
}
void SetName(const char* pszName) //设置员工姓名
{
strcpy(m_szName, pszName);
}
char* GetName()const //获取员工姓名
{
return (char*) m_szName;
}
void SetDepart(const char* pszDepart) //设置部门信息
{
strcpy(m_szDepart, pszDepart);
}
char* GetDepart()const //获取部门信息
{
return (char*) m_szDepart;
}
virtual void OutputName() //定义虚方法
{
cout << "员工姓名: " << m_szName << endl; //输出员工姓名
}
void OutputName(const char* pszName)
{
cout << "员工姓名: " << pszName << endl; //输出员工姓名
}
};
class COperator :public CEmployee //定义一个操作员类，从CEmployee类派生而来
{
private:
char m_szPassword[MAXLEN]; //定义密码
public:
COperator() //构造函数
{
memset(m_szPassword, 0, MAXLEN);
cout << "Operator构造函数被调用!" << endl;
}
void SetPassword(const char* pszPassword) //设置密码
{
strcpy(m_szPassword, pszPassword);
}
char* GetPassword()const //获取密码
{
return (char*) m_szPassword;
}
void OutputName() //定义虚方法
{
cout << "操作员姓名: " << m_szName << endl; //输出操作员姓名
}
};
int main(int argc, char* argv[])
{
CEmployee *pEmployee = new COperator(); //定义一个父类的指针对象，通过子类的构造函数构建
pEmployee->SetName("MR"); //调用SetName方法
pEmployee->OutputName(); //子类中的方法
pEmployee->OutputName("MRKJ");
return 0;
}3. Abstract class
Ordinary data members and functions can also be defined in abstract classes, but abstract classes cannot be instantiated. No matter how many methods a class has, as long as one method is an abstract method (virtual function), then the class is an abstract class.
// AbstractClass.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include "iostream.h"
#include "string.h"
#define MAXLEN 128 //定义一个宏
class CEmployee //定义一个抽象类
{
protected:
int m_nID; //定义员工ID
char m_szName[MAXLEN]; //定义员工姓名
char m_szDepart[MAXLEN]; //定义所属部门
public:
virtual void OutputName() = 0; //定义抽象方法
};
class COperator :public CEmployee //定义一个操作员类，从CEmployee类派生而来
{
public:
COperator()
{
strcpy(m_szName, "MR");
}
virtual void OutputName() //实现纯虚方法
{
cout << "操作员姓名: " << m_szName << endl; //输出操作员姓名
}
};
class CSystemManager :public CEmployee //定义一个管理类，从CEmployee类派生而来
{
public:
CSystemManager()
{
strcpy(m_szName, "MRSoft");
}
virtual void OutputName() //实现纯虚方法
{
cout << "系统管理员: " << m_szName << endl; //输出操作员姓名
}
};
int main(int argc, char* argv[])
{
CEmployee *pWorker; //定义CEmployee类型指针对象
pWorker = new COperator(); //调用COperator类的构造函数为pWorker赋值
pWorker->OutputName(); //调用COperator类的OutputName方法
delete pWorker; //释放pWorker对象
pWorker = NULL; //将pWorker对象设置为空
pWorker = new CSystemManager(); //调用CSystemManager类的构造函数与为pWorker赋值
pWorker->OutputName(); //调用CSystemManager类的OutputName方法
delete pWorker; //释放pWorker对象
pWorker = NULL; //将pWorker对象设置为空
return 0;
}
4. Multiple inheritance
Below is an example of multiple inheritance.
#include "stdafx.h"
#include "iostream.h"
class CBird //定义鸟类
{
public:
void FlyInSky() //定义成员函数
{
cout << "鸟能够在天空飞翔!" << endl; //输出信息
}
void Breath() //定义成员函数
{
cout << "鸟能够呼吸!" << endl; //输出信息
}
};
class CFish //定义鱼类
{
public:
void SwimInWater() //定义成员函数
{
cout << "鱼能够在水里游!" << endl; //输出信息
}
void Breath() //定义成员函数
{
cout << "鱼能够呼吸!" << endl; //输出信息
}
};
class CWaterBird: public CBird, public CFish //定义水鸟，从鸟和鱼类派生
{
public:
void Action() //定义成员函数
{
cout << "水鸟即能飞又能游!" << endl; //输出信息
}
};
int main(int argc, char* argv[])
{
CWaterBird Waterbird; //定义水鸟对象
Waterbird.FlyInSky(); //调用从鸟类继承而来的FlyInSky方法
Waterbird.SwimInWater(); //调用从鱼类继承而来的SwimInWater方法
return 0;
}5. Virtual inheritance
There is such a situation, class B and class C are both derived from class A, then when class D is derived from B and C, there will be two copies of class A. To solve this problem, C++ provides virtual inheritance, so that subclasses have a base class.
// VirtualInherited.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include "iostream.h"
class CAnimal //定义一个动物类
{
public:
CAnimal() //定义构造函数
{
cout << "动物类被构造!" << endl; //输出信息
}
void Move() //定义成员函数
{
cout << "动物能够移动!" << endl; //输出信息
}
};
class CBird : virtual public CAnimal //从CAnimal类虚继承CBird类
{
public:
CBird() //定义构造函数
{
cout << "鸟类被构造!" << endl; //输出信息
}
void FlyInSky() //定义成员函数
{
cout << "鸟能够在天空飞翔!" << endl; //输出信息
}
void Breath() //定义成员函数
{
cout << "鸟能够呼吸!\n" << endl; //输出信息
}
};
class CFish: virtual public CAnimal //从CAnimal类虚继承CFish
{
public:
CFish() //定义构造函数
{
cout << "鱼类被构造!" << endl; //输出信息
}
void SwimInWater() //定义成员函数
{
cout << "鱼能够在水里游!" << endl; //输出信息
}
void Breath() //定义成员函数
{
cout << "鱼能够呼吸!" << endl; //输出信息
}
};
class CWaterBird: public CBird, public CFish //从CBird和CFish类派生子类CWaterBird
{
public:
CWaterBird() //定义构造函数
{
cout << "水鸟类被构造!" << endl; //输出信息
}
void Action() //定义成员函数
{
cout << "水鸟即能飞又能游!" << endl; //输出信息
}
};
int main(int argc, char* argv[])
{
CWaterBird Waterbird; //定义水鸟对象
return 0;
}6. Summary
In program development, although multiple inheritance brings a lot of convenience, few people are willing to use it, because it will greatly increase program complexity and reduce maintainability, and the functions that can be achieved through multiple inheritance, single inheritance is completely Can. For example, C#, Java, etc. do not provide the function of multiple inheritance. They should also fully refer to C++, and have not adopted it after weighing it. Therefore, it should be used with caution when developing to avoid unnecessary trouble.