C++ Tutorial/Class/class definition — различия между версиями
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Версия 14:21, 25 мая 2010
Содержание
- 1 classes example
- 2 Class objects can be assigned to each other using default memberwise assignment
- 3 containership with employees and degrees
- 4 Create an object from a Class and call its function
- 5 Define a class with a member function that takes a parameter
- 6 Define class to record time
- 7 Define class with a data member and member functions to set and get its value
- 8 Define your first class
- 9 Friend Classes
- 10 Inner class
- 11 Instantiating multiple objects of the class using its constructor
- 12 Local Classes: A class may be defined within a function
classes example
#include <iostream>
#include <stdio.h>
using namespace std;
class Rectangle {
int x, y;
public:
void set_values (int,int);
int area (void) {return (x*y);}
};
void Rectangle::set_values (int a, int b) {
x = a;
y = b;
}
int main () {
Rectangle rect;
rect.set_values (3,4);
cout << "area: " << rect.area();
return 0;
}area: 12"
Class objects can be assigned to each other using default memberwise assignment
#include <iostream>
using std::cout;
using std::endl;
class Date
{
public:
Date( int = 1, int = 1, int = 2007 );
void print();
private:
int month;
int day;
int year;
};
Date::Date( int m, int d, int y )
{
month = m;
day = d;
year = y;
}
void Date::print()
{
cout << month << "/" << day << "/" << year;
}
int main()
{
Date date1( 8, 8, 2008 );
Date date2;
cout << "date1 = ";
date1.print();
cout << "\ndate2 = ";
date2.print();
date2 = date1;
cout << "\n\nAfter default memberwise assignment, date2 = ";
date2.print();
cout << endl;
return 0;
}date1 = 8/8/2008 date2 = 1/1/2007 After default memberwise assignment, date2 = 8/8/2008
containership with employees and degrees
#include <iostream>
#include <string>
using namespace std;
class student{
private:
string school;
string degree;
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:
string name;
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:
string title;
double dues;
employee emp;
student stu;
public:
void getdata(){
emp.getdata();
cout << " Enter title: "; cin >> title;
cout << " Enter golf club dues: "; cin >> dues;
stu.getedu();
}
void putdata() const{
emp.putdata();
cout << "\n Title: " << title;
cout << "\n Golf club dues: " << dues;
stu.putedu();
}
};
class scientist{
private:
int pubs;
employee emp;
student stu;
public:
void getdata(){
emp.getdata();
cout << " Enter number of pubs: "; cin >> pubs;
stu.getedu();
}
void putdata() const{
emp.putdata();
cout << "\n Number of publications: " << pubs;
stu.putedu();
}
};
class laborer{
private:
employee emp;
public:
void getdata(){ emp.getdata(); }
void putdata() const{ emp.putdata(); }
};
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;
}Create an object from a Class and call its function
#include <iostream>
using std::cout;
using std::endl;
class MyClass
{
public:
void displayMessage()
{
cout << "Welcome!" << endl;
}
};
int main()
{
MyClass obj;
obj.displayMessage();
return 0;
}Welcome!
Define a class with a member function that takes a parameter
#include <iostream>
using std::cout;
using std::cin;
using std::endl;
#include <string>
using std::string;
using std::getline;
class MyClass
{
public:
void displayMessage( string n )
{
cout << "Welcome \n" << n << "!"
<< endl;
}
};
int main()
{
string name;
MyClass obj;
cout << "Please enter the name:" << endl;
getline( cin, name );
cout << endl;
obj.displayMessage( name );
return 0;
}Please enter the name: Joe Welcome Joe!
Define class to record time
#include <iomanip>
#include <iostream>
using std::cout;
using std::endl;
using std::setfill;
using std::setw;
class Time
{
public:
Time();
void setTime( int, int, int );
void printUniversal();
void printStandard();
private:
int hour;
int minute;
int second;
};
Time::Time()
{
hour = minute = second = 0;
}
void Time::setTime( int h, int m, int s )
{
hour = h ;
minute = m;
second = s ;
}
void Time::printUniversal()
{
cout << setfill( "0" ) << setw( 2 ) << hour << ":" << setw( 2 ) << minute << ":" << setw( 2 ) << second;
}
void Time::printStandard()
{
cout << ( ( hour == 0 || hour == 12 ) ? 12 : hour "
<< setfill( "0" ) << setw( 2 ) << minute << ":" << setw( 2 )
<< second << ( hour < 12 ? " AM" : " PM" );
}
int main()
{
Time t;
t.printUniversal();
t.printStandard();
t.setTime( 1, 2, 6 );
t.printUniversal();
t.printStandard();
t.setTime( 99, 99, 99 );
t.printUniversal();
t.printStandard();
return 0;
}00:00:0012:00:00 AM01:02:061:02:06 AM99:99:993:99:99 PM
Define class with a data member and member functions to set and get its value
#include <iostream>
using std::cout;
using std::cin;
using std::endl;
#include <string>
using std::string;
using std::getline;
class MyClass
{
public:
void setName( string name )
{
name = name;
}
string getName()
{
return name;
}
void displayMessage()
{
cout << "Welcome to the grade book for\n" << getName() << "!" << endl;
}
private:
string name;
};
int main()
{
string n;
MyClass obj;
cout << "Initial name is: " << obj.getName() << endl;
cout << "\nPlease enter the name:" << endl;
getline( cin, n );
obj.setName( n );
cout << endl;
obj.displayMessage();
return 0;
}Initial name is: Please enter the name: Joe Welcome to the grade book for !
Define your first class
#include <iostream>
using namespace std;
class ThreeDimension {
public:
int X;
int Y;
int Z;
};
int main() {
ThreeDimension myDimension;
int range;
// Assign values to fields in myDimension.
myDimension.X = 7;
myDimension.Y = 16;
myDimension.Z = 21;
// Compute the range assuming a full tank of gas.
range = myDimension.Y * myDimension.Z;
cout << range;
return 0;
}336
Friend Classes
#include <iostream>
using namespace std;
class TwoValues {
int a;
int b;
public:
TwoValues(int i, int j) { a = i; b = j; }
friend class Min;
};
class Min {
public:
int min(TwoValues x);
};
int Min::min(TwoValues x)
{
return x.a < x.b ? x.a : x.b;
}
int main()
{
TwoValues ob(10, 20);
Min m;
cout << m.min(ob);
return 0;
}Inner class
#include <iostream>
using namespace std;
class Outer
{
public:
Outer(void)
{ cout << "Just instantiated an outer\n";
outer_data = 2002;
};
class Inner
{
public:
Inner(void)
{
cout << "Just instantiated an inner\n";
inner_data = 1001;
};
void show_data(void) { cout << "Inner: " << inner_data << endl; };
private:
int inner_data;
} inside_stuff;
void show_all_data(void)
{
inside_stuff.show_data();
cout << "Outer: " << outer_data << endl;
};
private:
int outer_data;
};
int main(void)
{
Outer my_data;
my_data.show_all_data();
}Instantiating multiple objects of the class using its constructor
#include <iostream>
using std::cout;
using std::endl;
#include <string>
using std::string;
class MyClass
{
public:
MyClass( string name )
{
setName( name );
}
void setName( string n )
{
name = n;
}
string getName()
{
return name;
}
void displayMessage()
{
cout << "Welcome " << getName() << "!" << endl;
}
private:
string name;
};
int main()
{
MyClass obj1( "A" );
MyClass obj2( "B" );
cout << obj1.getName()<< "\n" << obj2.getName() << endl;
return 0;
}A B
Local Classes: A class may be defined within a function
#include <iostream>
using namespace std;
void f();
int main()
{
f();
return 0;
}
void f()
{
class myclass {
int i;
public:
void put_i(int n) { i=n; }
int get_i() { return i; }
} ob;
ob.put_i(10);
cout << ob.get_i();
}