C++/Class/Instance

class array and object method call

<source lang="cpp">

1. include <iostream>
2. include <iomanip>
3. include <string.h>

using namespace std; class Book {

 public: 
   void show_title(void) { cout << title << "\n"; };
   void show_book(void) { show_title(); show_publisher(); };
   void assign_members(char *, char *, char *, float);
 private:
   char title[256];
   char author[64];
   float price;
   char publisher[256];
   void show_publisher(void) { cout << publisher << "\n"; };

};

void Book::assign_members(char *title, char *author, char *publisher,float price) {

  strcpy(Book::title, title);
  strcpy(Book::author, author);
  strcpy(Book::publisher, publisher);
  Book::price = price;

}

int main(void) {

  Book Library[4];
  Library[0].assign_members("A", "B","C", 49.95);
  Library[1].assign_members("D", "E", "F", 54.95); 
  Library[2].assign_members("G", "H","I", 49.95);
  Library[3].assign_members("J", "K","L", 24.95);

  for (int i = 0; i < 4; i++)
    Library[i].show_book();

}

 </source>

Construct object in an object array one by one

<source lang="cpp">

1. include <iostream>
2. include <iomanip>
3. include <string.h>

using namespace std; class Book {

 public: 
   void show_title(void) { cout << title << "\n"; };
   void show_book(void) 
   { 
     show_title();
     show_publisher();
   };
   Book(char *title, char *author, char *publisher, float price);
 private:
   char title[256];
   char author[64];
   float price;
   char publisher[256];
   void show_publisher(void) { cout << publisher << "\n"; };

}; Book::Book(char *title, char *author, char *publisher, float price)

{
  strcpy(Book::title, title);
  strcpy(Book::author, author);
  strcpy(Book::publisher, publisher);
  Book::price = price;
  cout << "In constructor." << endl;
}

int main(void)

{
  Book *Library[4];
  int i;
  Library[0] = new Book("A", "B","C", 49.95);
  Library[1] = new Book("D", "E", "F", 54.95);
  Library[2] = new Book("G", "H","I", 49.95);
  Library[3] = new Book("K", "J","P", 29.95);
  for (i = 0; i < 4; i++)
    Library[i]->show_book();
}
 
   
   
 </source>

Declare the instance variable for a class

<source lang="cpp">

1. include <iostream>

using namespace std; class Power {

 double b;
 
 int e;
 
 double val;

public:

 Power(double base, int exp);
 
 double getPower() { 
    return val; 
 }

}; Power::Power(double base, int exp) {

 b = base;
 e = exp;
 val = 1;
 if(exp == 0) 
    return;
 for( ; exp > 0; exp--) 
    val = val * b;

} int main() {

 Power x(4.0, 2), y(2.5, 1), z(5.7, 0);
 cout << x.getPower() << " ";
 cout << y.getPower() << " ";
 cout << z.getPower() << endl;
 return 0;

}

 </source>

Loop through an object array and call its method

<source lang="cpp">

1. include <iostream>
2. include <iomanip>
3. include <string.h>

using namespace std; class Book {

 public: 
   void show_title(void) { cout << title << "\n"; };
   void show_book(void) 
   { 
     show_title();
     show_publisher();
   };
   Book(char *title, char *author, char *publisher, float price);
   ~Book(void) { cout << "Destroying the entry for " << title << endl; };
 private:
   char title[256];
   char author[64];
   float price;
   char publisher[256];
   void show_publisher(void) { cout << publisher << "\n"; };

}; Book::Book(char *title, char *author, char *publisher, float price) {

  strcpy(Book::title, title);
  strcpy(Book::author, author);
  strcpy(Book::publisher, publisher);
  Book::price = price;

} int main(void) {

  Book *Library[4];
  int i = 0;
  Library[0] = new Book("A", "B","C", 49.95);
  Library[1] = new Book("D", "E", "F", 54.95);
  Library[2] = new Book("G", "H","I", 49.95);
  Library[3] = new Book("J", "K","P", 24.95);
  for (i = 0; i < 4; i++)
    Library[i]->show_book();
  for (i = 0; i < 4; i++)
    delete Library[i];

}

 </source>