policy class

[cjj]

practice how to make policy class.

Homedepot (HD) hires two furniture factories: ChineseFurnitureFactory and SpanishFurnitureFactory to make doors and floors.


class Wood
{
public:
int a;

Wood(int a=3)
{
this->a = a;
}

friend ostream& operator<<(ostream& out, Wood a)
{
out << a.a << " " ;
return out;
}

Wood& operator*(int n)
{
a *= n;
return *this;
}

};


template <typename T>
class FurnitureFactory
{
public:
typedef T Door;
typedef T Floor;

virtual void cutWood(T a) = 0;
virtual Door makeDoor() = 0;
virtual Floor makeFloor() =0;

virtual ~FurnitureFactory(){}
};


template <typename T>
class ChineseFurnitureFactory : public FurnitureFactory<T>
{
T a;
public:
void cutWood(T a)
{
cout << a.a << " is cut into 2 x 4 x 8 in wood factory" << endl;
this->a = a * 100;
}

typename FurnitureFactory<T>::Door makeDoor()
{
typename::FurnitureFactory<T>::Door result = a ;
return result;
}

typename::FurnitureFactory<T>::Floor makeFloor()
{
typename::FurnitureFactory<T>::Floor result = a;
return result;
}

};

template <typename T>
class SpanishFurnitureFactory : public FurnitureFactory<T>
{
T a;
public:
void cutWood(T a)
{
cout << a.a << " is cut into 1 x 2 x 4 in wood factory" << endl;
this->a = a;
}

typename::FurnitureFactory<T>::Door makeDoor()
{
typename::FurnitureFactory<T>::Door result = a ;
return result;
}

typename::FurnitureFactory<T>::Floor makeFloor()
{
typename::FurnitureFactory<T>::Floor result = a;
return result;
}

};


template < typename T = Wood,
int N = 3,
typename O = ChineseFurnitureFactory<T> >
class HD
{
O ops;
T a;
static const int b = N;
public:

void sellDoor(T a)
{
ops.cutWood(a);
typename O::Door d = ops.makeDoor();
cout << N << " doors made of " << d << " are sold " << endl;
}

void sellFloor(T a)
{
ops.cutWood(a);
typename O::Floor d = ops.makeFloor();
cout << N << " Floors made of " << d << " are sold " << endl;
}

};



Wood dr(300);
Wood dr2(400);
HD<Wood> hd;
hd.sellDoor(dr);
hd.sellFloor(dr2);


cout << " ------------" << endl;

HD<Wood, 5, SpanishFurnitureFactory<Wood> > hd3;
hd3.sellDoor(dr);
hd3.sellFloor(dr2);

[NUj6URfi]

Why are you posting this?

[cjj]

practice policy class and keep track of where I'm on c++. Hopefully can get some of your opinions on the topic.

[MikeyBoy]

Nowhere have you given us even the slightest bit of information about what this "policy" class is, and what it's supposed to do.

Are you referring to this:

http://en.wikipedia.org/wiki/Policy-based_design

?

EDIT: And use code tags when posting code.

[cjj]

Yes, thanks for the link. In the link, inheritance is used between the execution class(HelloWorld) and policy classes, which I didn't do in my example. In my example, ChineseFurnitureFactory and SpanishFurnitureFactory
are the policy classes. Execution class HD (Homedepot) can hire two different factories to make furniture for it using a material (template parameter T), for example, class Wood. When HD calls sellDoor() / sellFloor(), it will sell
different styles of door/floor depending on which factory ( policy class ) it uses.

By the way, I intentionally added some default values in the declaration of class HD as part of practicing template programming. I will be focusing on template programming recently, so it's likely I will post similar threads in the near future.

template < typename T = Wood,
int N = 3,
typename O = ChineseFurnitureFactory<T> >
class HD