The inheritance of C + + __c++

1 Why to inherit
Implement code reuse.
When instantiating a derived class object, the base class constructor is called first, and the derived class constructor is invoked;
When destroying a derived class object, the destructor call order is just the opposite

#include <iostream>
#include <string>
using namespace std;

Class person{public
: Person
    () {
        cout << ' person () ' << Endl
    }
    ~person () {
        cout << "~person ()" << Endl;
    }
    void Eat () {
        cout << "Eat ()" << Endl;
    }
    string M_strname;
    int m_iage;

};


Class worker:p ublic person{public
:
    worker () {
        cout << "worker ()" << Endl;
    }
    ~worker () {
        cout << "~worker ()" << Endl;
    }
    void Worker () {
        cout << "worker ()" << Endl;
    }
    int m_isalary;

};

int main () {
    worker *pworker = new Worker ();

    Delete Pworker;
    Pworker = NULL;
    return 0;
}

2) Way of inheriting
A. Public inheritance
Class A:public B

Base class      public      protected       private
derived class    public       protected       not accessible

b) Protection of inheritance
Class a:protected B

Base class      public          protected       private
derived class    protected        protected       unreachable

c) Private inheritance
Cladd a:private B

Base class      public      protected       private
derived class    private      private         cannot access

3) Hide and overwrite
The parent class void F ();
Subclass void F ();
When instantiating a subclass object, only the subclass's F () is accessible, and the F () of the parent class is hidden;
Summary: Parent-child relationship members are hidden with the same name

Overlay refers to a derived class function that overrides a base class function, characterized by:
Different ranges (in derived classes and base classes, respectively);
The function name is the same;
parameters are the same;
The base class function must have a virtual keyword.

4) is_a Relationship
Eg: humans are the base class, derived classes are soldiers and workers, soldiers and workers are human beings.
A derived class object can be converted to a base class object, whereas it cannot be

5 multiple inheritance and multiple inheritance
Multiple inheritance Human-> Soldier Class-> Infantry class
Multiple inheritance: A derived class has more than one base class

Class worker{};
Class farmer{};
Class Migrantworker:ppublic Worker.public farmer{}; By default, #include <iostream> #include <string> with private inheritance

using namespace Std;
        Class farmer{Public:farmer (String name= "Jack") {m_strname = name;
    cout << "Farmer ()" << Endl;
    Virtual ~farmer () {cout << "~farmer ()" << Endl;
} void Sow ();
Protected:string M_strname;
};
    void Farmer::sow () {cout << m_strname << Endl;
cout << "Farmer--souw ()" << Endl;
        Class worker{Public:worker (String code= "001") {m_strcode = code;
    cout << "Worker ()" << Endl;
    Virtual ~worker () {cout << "~worker ()" << Endl;
        } void Carry () {cout << m_strcode << Endl;
    cout << "Worker--carry ()" << Endl;
} protected:string M_strcode;

}; Class Migrantworker:public Farmer,public worker{Public:migrantworker (sTring name, string code);
    ~migrantworker () {cout << "~migrantworker ()" << Endl;
}
}; Migrantworker::migrantworker (string name, String code): Farmer (name), Worker (code) {//constructor consistent with initialization list order cout << Mig
Ranworker () "<< Endl;
    int main () {Migrantworker *p = new Migrantworker ("Huheqing", "112");
    P->carry ();
    P->sow ();
    Delete p;
    p = NULL;
return 0; }

6) Virtual inheritance

Diamond Inheritance
With multiple inheritance and multiple inheritance, there are data redundancy problems
Class worker:virtual Public person{

};
Class farmer:virtual Public person{

};
Class migranfarmer:public worker,public farmer{

};
Note: In multiple inheritance or multiple inheritance, when an object is instantiated, the arguments of the parent class with the parameter's constructor are passed through the constructor initialization list of the subclass

#include <iostream> #include <string> using namespace std;
        Class person{Public:person (String color= "Blue") {m_strcolor = color;
    cout << "person ()" << Endl;
    Virtual ~person () {cout << "~person ()" << Endl;
        } void Printcolor () {cout << m_strcolor << Endl;
    cout << "Printcolor ()" << Endl;
} protected:string M_strcolor;
};
        Class Farmer:virtual Public person{public:farmer (string name = "Jack", String color = "Blue"):P Erson (color) {
        M_strname = name;
    cout << "Farmer ()" << Endl;
    Virtual ~farmer () {cout << "~farmer ()" << Endl;
} void Sow ();
Protected:string M_strname;
};
    void Farmer::sow () {cout << m_strname << Endl;
cout << "Farmer--souw ()" << Endl; Class Worker:virtual Public person{public:worker (String code = "001", String color = "Blue"):P Erson (colOR) {M_strcode = code;
    cout << "Worker ()" << Endl;
    Virtual ~worker () {cout << "~worker ()" << Endl;
        } void Carry () {cout << m_strcode << Endl;
    cout << "Worker--carry ()" << Endl;
} protected:string M_strcode;

};
    Class Migrantworker:public Farmer,public worker{public:migrantworker (string name, string code,string color);
    ~migrantworker () {cout << "~migrantworker ()" << Endl;
}
}; Migrantworker::migrantworker (string name, string code,string color): Farmer (Name,color), Worker (Code,color) {//
Constructors are consistent with the initialization list order cout << "Migranworker ()" << Endl;
    int main () {Migrantworker *p = new Migrantworker ("Huheqing", "112", "Black");
    P->carry ();
    P->sow ();
    Delete p;
    p = NULL;
return 0; }