C++ Tutorial/Class/multiple base classes

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An example of multiple base classes.

<source lang="cpp">#include <iostream> using namespace std;

class BaseClass1 { protected: 

 int x;

public: 

 void showx() { cout << x << "\n"; }

};

class BaseClass2 { protected: 

 int y;

public: 

 void showy() { cout << y << "\n"; }

};

// Inherit multiple base classes. class DerivedClass: public BaseClass1, public BaseClass2 { public: 

 /* x and y are accessible because they are 
    protected in BaseClass1 and BaseClass2, not private. */ 
 void set(int i, int j) { x = i; y = j; }

};

int main() { 

 DerivedClass ob; 

 ob.set(10, 20); // provided by DerivedClass 
 ob.showx();     // from BaseClass1 
 ob.showy();     // from BaseClass2 

 return 0;

}</source> 

10
20

In cases of multiple inheritance: Constructors are called in order of derivation, destructors in reverse order

<source lang="cpp">#include <iostream> using namespace std;

class base { public: 

 base() { cout << "Constructing base\n"; }
 ~base() { cout << "Destructing base\n"; }

};

class derived1 : public base { public: 

 derived1() { cout << "Constructing derived1\n"; }
 ~derived1() { cout << "Destructing derived1\n"; }

};

class derived2: public derived1 { public: 

 derived2() { cout << "Constructing derived2\n"; }
 ~derived2() { cout << "Destructing derived2\n"; }

};

int main() { 

 derived2 ob;
  
 // construct and destruct ob
  
 return 0;

}</source>

Multiple inheritance example

<source lang="cpp">#include <iostream> using std::ostream; using std::cout; using std::endl; class Base1 { public: 

  Base1( int parameterValue )
  {
     value = parameterValue;
  }
  int getData() const
  {
     return value;
  }

protected: 

  int value;

}; class Base2 { public: 

  Base2( char characterData )
  {
     letter = characterData;
  }
  char getData() const
  {
     return letter;
  }

protected: 

  char letter;

}; class Derived : public Base1, public Base2 { public: 

  Derived( int integer, char character, double double1 )
     : Base1( integer ), Base2( character ), real( double1 ) { }
  double getReal() const {
     return real;
  }
   void display()
   {
      cout << "    Integer: " << value << "\n  Character: "
         << letter << "\nReal number: " << real;
   }

private: 

  double real;

};

int main() { 

  Base1 base1( 10 ), *base1Ptr = 0;
  Base2 base2( "Z" ), *base2Ptr = 0;
  Derived derived( 7, "A", 3.5 );
  cout << base1.getData()
       << base2.getData();
  derived.display();
  cout << derived.Base1::getData()
       << derived.Base2::getData()
       << derived.getReal() << "\n\n";
  base1Ptr = &derived;
  cout << base1Ptr->getData() << "\n";
  base2Ptr = &derived;
  cout << base2Ptr->getData() << endl;
  return 0;

}</source> 

10Z    Integer: 7
  Character: A
Real number: 3.57A3.5
7
A

Multiple Inheritance in both private and public way

<source lang="cpp">#include <iostream> using namespace std; class One { 

public:
 One(void) 
 { 
   cout << "Constructor for One\n"; 
   one = 1;
 };
 int one;

}; class Two { 

public:
 Two(void) 
 { 
   cout << "Constructor for Two\n";
   two = 2;
 };
 int two;

}; class Three { 

public:
 Three(void) 
 { 
   cout << "Constructor for Three\n"; 
   three = 3;
 };
 int three;

}; class Derived: private One, private Three, public Two { 

public:
  Derived(void) : One(), Two(), Three() 
  {
    cout << "Derived constructor called\n"; };
  void show_value(void) { cout << one << two << three << endl; };

}; int main(void) { 

  Derived my_class;
  my_class.show_value();
  cout << my_class.two;

}</source>

Multiple Inheritance to have the features from both parent

<source lang="cpp">#include <iostream> using std::cout; using std::cin; using std::endl; class Horse { 

 public:
   Horse() { cout << "Horse constructor... "; }
   virtual ~Horse() { cout << "Horse destructor... "; }
   virtual void Whinny() const { cout << "Whinny!... "; }
 private:
   int itsAge;

}; class Bird { 

 public:
   Bird() { cout << "Bird constructor... "; }
   virtual ~Bird() { cout << "Bird destructor... "; }
   virtual void Chirp() const { cout << "Chirp... ";  }
   virtual void Fly() const
   {
      cout << "fly! ";
   }
 private:
   int itsWeight;

}; class Pegasus : public Horse, public Bird { 

 public:
   void Chirp() const { Whinny(); }
   Pegasus() { cout << "Pegasus constructor... "; }
   ~Pegasus() { cout << "Pegasus destructor...  "; }

}; const int MagicNumber = 2; int main(){ 

  Horse* Ranch[MagicNumber];
  Bird* Aviary[MagicNumber];
  Horse * pHorse;
  Bird * pBird;
  
  pHorse = new Pegasus;
  pHorse = new Horse;
  Ranch[0] = pHorse;
  pBird = new Pegasus;
  pBird = new Bird;
  Aviary[0] = pBird;
  Ranch[0]->Whinny();
  delete Ranch[0];
  
  Aviary[0]->Chirp();
  Aviary[0]->Fly();
  delete Aviary[0];
  return 0;

}</source>

multiple inheritance with employees and degrees

<source lang="cpp">#include <iostream> 

 using namespace std;  
 const int LEN = 80;    
 class student{  
    private:  
       char school[LEN];
       char degree[LEN];
    public:  
       void getedu(){  
          cout << "   Enter name of school or university: ";  
          cin >> school;  
          cout << "   Enter highest degree earned \n";  
          cout << "   (Highschool, Bachelor"s, Master"s, PhD): ";  
          cin >> degree;  
       }  
       void putedu() const  
       {  
          cout << "\n   School or university: " << school;  
          cout << "\n   Highest degree earned: " << degree;  
       }  
   };  
 class employee{  
    private:  
       char name[LEN];
       unsigned long number;
    public:  
       void getdata(){  
          cout << "\n   Enter last name: "; cin >> name;  
          cout << "   Enter number: ";      cin >> number;  
       }  
       void putdata() const  
       {  
          cout << "\n   Name: " << name;  
          cout << "\n   Number: " << number;  
       }  
   };  
 class manager : private employee, private student {  
    private:  
       char title[LEN];        
       double dues;            
    public:  
       void getdata(){  
          employee::getdata();  
          cout << "   Enter title: ";          cin >> title;  
          cout << "   Enter golf club dues: "; cin >> dues;  
          student::getedu();  
       }  
       void putdata() const  
       {  
          employee::putdata();  
          cout << "\n   Title: " << title;  
          cout << "\n   Golf club dues: " << dues;  
          student::putedu();  
       }  
 };  
 class scientist : private employee, private student {  
    private:  
       int pubs;     
    public:  
       void getdata(){  
          employee::getdata();  
          cout << "   Enter number of pubs: "; cin >> pubs;  
          student::getedu();  
       }  
       void putdata() const  
       {  
          employee::putdata();  
          cout << "\n   Number of publications: " << pubs;  
          student::putedu();  
       }  
 };  
 class laborer : public employee    
   {  
 };  
 int main(){  
    manager m1;  
    scientist s1, s2;  
    laborer l1;  
   
    cout << endl;  
    cout << "\nEnter data for manager 1";    
    m1.getdata();                            
   
    cout << "\nEnter data for scientist 1";  
    s1.getdata();  
   
    cout << "\nEnter data for scientist 2";  
    s2.getdata();  
   
    cout << "\nEnter data for laborer 1";  
    l1.getdata();  
   
    cout << "\nData on manager 1";           
    m1.putdata();                            
   
    cout << "\nData on scientist 1";  
    s1.putdata();  
   
    cout << "\nData on scientist 2";  
    s2.putdata();  
   
    cout << "\nData on laborer 1";  
    l1.putdata();  
    cout << endl;  
    return 0;  
 }</source>

multiple inheritance with English Distances

<source lang="cpp">#include <iostream> 

 #include <string>  
 using namespace std;  
 class Type{  
    private:  
       string dimensions;  
       string grade;  
    public:                        
       Type() : dimensions("N/A"), grade("N/A"){  }  
                                   
       Type(string di, string gr) : dimensions(di), grade(gr)  
       {  }  
       void gettype(){  
          cout << "   Enter nominal dimensions (2x4 etc.): ";  
          cin >> dimensions;  
          cout << "   Enter grade (rough, const, etc.): ";  
          cin >> grade;  
       }  
       void showtype() const       
       {  
          cout << "\n   Dimensions: " << dimensions;  
          cout << "\n   Grade: " << grade;  
       }  
 };
 class Distance{  
    private:  
       int feet;  
       float inches;  
    public:    
       Distance() : feet(0), inches(0.0){  } 
       Distance(int ft, float in) : feet(ft), inches(in)  
         {  }  
       void getdist(){  
          cout << "   Enter feet: ";  cin >> feet;  
          cout << "   Enter inches: ";  cin >> inches;  
       }  
       void showdist() const       
       { cout  << feet << "\"-" << inches << "\""; }  
 };
 class Lumber : public Type, public Distance  {  
    private:  
       int quantity;                      
       double price;                      
    public:                               
       Lumber() : Type(), Distance(), quantity(0), price(0.0)  
       {  }  
       Lumber( string di, string gr,      
               int ft, float in,          
               int qu, float prc ) :      
               Type(di, gr),              
               Distance(ft, in),          
               quantity(qu), price(prc)   
       {  }  
       void getlumber()  
       {  
          Type::gettype();  
          Distance::getdist();  
          cout << "   Enter quantity: "; cin >> quantity;  
          cout << "   Enter price per piece: "; cin >> price;  
       }  
       void showlumber() const  
       {  
          Type::showtype();  
          cout << "\n   Length: ";  
          Distance::showdist();  
          cout << "\n   Price for " << quantity  
              << " pieces: $" << price * quantity;  
       }  
 };  
 int main(){  
    Lumber siding;                   
    siding.getlumber();              
    Lumber studs( "2x4", "const", 8, 0.0, 200, 4.45F );  
   
    cout << "\nSiding";  siding.showlumber();  
    cout << "\nStuds";     studs.showlumber();  
    cout << endl;  
    return 0;  
   }</source>

Resolving Ambiguity in Case of Multiple Inheritance Involving Common Base Classes

<source lang="cpp">#include <iostream> using namespace std; typedef int HANDS; enum COLOR { Red, Green, Blue, Yellow, White, Black, Brown } ; class Animal { 

 public:
   Animal(int);
   virtual ~Animal() { cout << "Animal destructor...\n"; }
   virtual int GetAge() const { return itsAge; }
   virtual void SetAge(int age) { itsAge = age; }
 private:
   int itsAge;

}; Animal::Animal(int age): itsAge(age) { 

  cout << "Animal constructor...\n";

} class Horse : public Animal { 

 public:
   Horse(COLOR color, HANDS height, int age);
   virtual ~Horse() { cout << "Horse destructor...\n"; }
   virtual void Whinny()const { cout << "Whinny!... "; }
   virtual HANDS GetHeight() const { return itsHeight; }
   virtual COLOR GetColor() const { return itsColor; }
 protected:
   HANDS itsHeight;
   COLOR itsColor;

}; Horse::Horse(COLOR color, HANDS height, int age): Animal(age), itsColor(color),itsHeight(height) { 

  cout << "Horse constructor...\n";

} class Bird : public Animal { 

 public:
   Bird(COLOR color, bool migrates, int age);
   virtual ~Bird() {cout << "Bird destructor...\n";  }
   virtual void Chirp()const { cout << "Chirp... ";  }
   virtual void Fly()const{ cout << "fly! "; }
   virtual COLOR GetColor()const { return itsColor; }
   virtual bool GetMigration() const { return itsMigration; }
 protected:
   COLOR itsColor;
   bool itsMigration;

}; Bird::Bird(COLOR color, bool migrates, int age): Animal(age), itsColor(color), itsMigration(migrates) { 

  cout << "Bird constructor...\n";

} class Pegasus : public Horse, public Bird { 

 public:
   void Chirp()const { Whinny(); }
   Pegasus(COLOR, HANDS, bool, long, int);
   virtual ~Pegasus() {cout << "Pegasus destructor...\n";}
   virtual long GetNumberBelievers() const
   { return  itsNumberBelievers; }
   virtual COLOR GetColor()const { return Horse::itsColor; }
   virtual int GetAge() const { return Horse::GetAge(); }
 private:
   long itsNumberBelievers;

}; Pegasus::Pegasus( 

  COLOR aColor,
  HANDS height,
  bool migrates,
  long NumBelieve,
  int age):
  Horse(aColor, height,age),
  Bird(aColor, migrates,age),
  itsNumberBelievers(NumBelieve)

{ 

  cout << "Pegasus constructor...\n";

} int main() { 

  Pegasus *pPeg = new Pegasus(Red, 5, true, 10, 2);
  int age = pPeg->GetAge();
  cout << "This pegasus is " << age << " years old.\n";
  delete pPeg;
  return 0;

}</source>

Источник — «http://cppe.ru/index.php?title=C%2B%2B_Tutorial/Class/multiple_base_classes&oldid=2272»