C++/Class/Base Class
Содержание
Base class and derived class
#include <iostream>
using namespace std;
class BaseClass {
int i, j;
public:
void set(int a, int b) {
i = a;
j = b;
}
void show() {
cout << i << " " << j << endl;
}
};
class DerivedClass : public BaseClass {
int k;
public:
DerivedClass(int x) {
k = x;
}
void showk() {
cout << k << endl;
}
};
int main()
{
DerivedClass ob(3);
ob.set(1, 2); // access member of BaseClass
ob.show(); // access member of BaseClass
ob.showk(); // uses member of DerivedClass class
return 0;
}
class to represent a book
#include <iostream>
#include <iomanip>
#include <string.h>
using namespace std;
class Book
{
public:
char title[256];
char author[64];
float price;
void show_title(void) { cout << title << "\n"; };
float get_price(void) { return(price); };
void show_book(void);
void assign_publisher(char *name) { strcpy(publisher, name); };
private:
char publisher[256];
void show_publisher(void) { cout << publisher << "\n"; };
};
void Book::show_book(void)
{
show_title();
show_publisher();
};
int main(void)
{
Book tips, diary;
strcpy(tips.title, "C");
strcpy(tips.author, "D");
tips.price = 49.95;
tips.assign_publisher("E");
strcpy(diary.title, "F");
strcpy(diary.author, "G");
diary.price = 9.95;
diary.assign_publisher("None");
tips.show_book();
diary.show_book();
}
Init member variables from base class
#include <iostream>
using namespace std;
class BaseClass {
int i, j;
public:
BaseClass(int x, int y) {
i = x;
j = y;
}
void showij() {
cout << i << " " << j << "\n";
}
};
class DerivedClass : public BaseClass {
int k;
public:
DerivedClass(int a, int b, int c) : BaseClass(b, c) {
k = a;
}
void show() {
cout << k << " "; showij();
}
};
int main()
{
DerivedClass ob(1, 2, 3);
ob.show();
return 0;
}
Pass arguments to base class
#include <iostream>
using namespace std;
class BaseClass {
int i;
public:
BaseClass(int n) {
cout << "Constructing base class\n";
i = n;
}
~BaseClass() {
cout << "Destructing base class\n";
}
void showi() {
cout << i << "\n";
}
};
class DerivedClass : public BaseClass {
int j;
public:
DerivedClass(int n, int m) : BaseClass(m) {
cout << "Constructing DerivedClass class\n";
j = n;
}
~DerivedClass() {
cout << "Destructing DerivedClass class\n";
}
void showj() {
cout << j << "\n";
}
};
int main()
{
DerivedClass o(10, 20);
o.showi();
o.showj();
return 0;
}
Use Base keyword to call method in parent class from subclass
#include <iostream>
using namespace std;
class Base {
public:
void display(void) { cout << "This is the base class" << endl; };
};
class Derived: public Base {
public:
void display(void) { cout << "This is the derived class" << endl; };
};
int main(void){
Derived my_class;
my_class.display();
my_class.Base::display();
}
Using base pointers on DerivedClass class objects.
//
#include <iostream>
#include <cstring>
using namespace std;
class BaseClass {
char author[80];
public:
void put_author(char *s) {
strcpy(author, s);
}
void show_author() {
cout << author << endl;
}
} ;
class DerivedClass : public BaseClass {
char title[80];
public:
void put_title(char *num) {
strcpy(title, num);
}
void show_title() {
cout << "Title: ";
cout << title << endl;
}
};
int main()
{
BaseClass *p;
BaseClass baseObject;
DerivedClass *dp;
DerivedClass derivedObject;
p = &baseObject;
p->put_author("Tom Clancy");
p = &derivedObject;
p->put_author("William Shakespeare");
baseObject.show_author();
derivedObject.show_author();
cout << endl;
dp = &derivedObject;
dp->put_title("The Tempest");
p->show_author();
dp->show_title( );
return 0;
}