properties

1. properties • Methods of a class can manipulate that class’s private data members • Classes provide public properties to allow clients to set ( assign value to) or get(obtain value of) private data members • __property void set_Hour( int val) • { • hour = (val >=0 &&val<24)?val:0); • } • __property int get_Hour() • { • return hour; • }

2. properties • Providing set and get capabilities appears to be the same as making the variables public • Every property method name must be preceded by either set_ or get_ • __property void set_propertyName() • PropertyName specifies the name of property. • Hour is scalar property • Scalar property is property that can be accessed like variables. We assign value to scalar properties using = operator. When assignment occurs, the code in the set accessor for that property executes • Time *time = new Time(); • time->Hour = Int32::Parse(Console::ReadLine());

3. Static members • Static variable: all class objects share only one copy of a static variable. • Static variable represents class-wide information • Declaration • static in count; • Static member can be initialized in its declaration • Public static data can be accessed from client code through the class name using the scope resolution operator:: • The private static data can be accessed only through methods or property of the class

4. Static methods • To enable a client to access a private static member when no objects of the class exists, the class must provide a public static method or property • A static method cannot access non-static data • Static variable and static methods exist even when there are no objects of that class in which the static members are defined

5. Inheritance • The previously defined class is called the base class • New class is referred to as the derived class • (other language, Java refer to base as superclass and derived class as subclass)

6. Point class • public __gc class Point • { • public: • Point(); • Point(int, int); • __property int get_X(){return x;} • __property void set_X(int val){x = val;} • __property int get_Y(){ return y;} • __property void set_Y(int val){ y = val;} • String *ToString(); • private: • int x,y; • };

7. String * Point::ToString() • { • return String::Concat(S”[“,x.ToString(), S”,”,y.ToString(), S”]”); • } • Point::Point(){ } • Point::Point( int xval, int yval) • { • x = xval; • y = yval; • }

8. Circle – inherit Point class • public __gc class Circle :public Point • { • public: • Circle(); • Circle( int,int,double); • __property double get_Radius(){return radius;} • __property void set_Radius(double r) • {if( r > 0) radius = r;} • double Diameter(); • double Area(); • double Circumference(); • String *ToString(); • private: • double radius; • };

9. Circle • Circle::Circle(){} • Circle::Circle(int xval,int yval, double r) :Point(xval,yval) • { radius = r;} • double Circle::Diameter(){ return radius *2;} • } • double Circle::Circumference() • { • return Math::PI *Diameter(); • } • double Circle::Area() • { return Math::PI * Math::Pow(radius, 2);} • String *Circle::ToString() • { return String::Concat(S”center= “, __super::ToString(), S”;Radius = “, Radius.ToString()); • }

10. int _tmain() • { • Circle *cir = new Circle(4,5,2.5); • String *output = String::Concat(S”X coordinate is “, cir->X.ToString(), S”\nY coordinate is “, cir->Y.ToString(), S”\nRadius is “, cir->Radius.ToString()); • Return 0; • }

11. Assignment • Define a class called Cylinder that inherits from Circle. • Has data member height • Methods: Volume() that return volume of the cylinder • Area() return the cylinder’s surface area • Properties: set_Height and get_Height

12. int _tmain() { Cylinder *cyn = new Cylinder(12,23,2.5,5.7); String *out = String::Concat (S"X coordinate is ", cyn->X.ToString(), S"\nY coordinate is ", cyn->Y.ToString(),S"\nRadius is ", cyn->Radius.ToString(),S"\nHeight is ", cyn->Height.ToString()); out = String::Concat (out, S"\nDiameter is ", cyn->Diameter().ToString(S"F"), S"\n"); out = String::Concat (out, S"Volume is", cyn->Volume().ToString(S"F")); MessageBox::Show (out, S"Demonstrating class Cylinder"); return 0; }