policy class

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);


Why are you posting this?
practice policy class and keep track of where I'm on c++. Hopefully can get some of your opinions on the topic.
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.
Last edited on
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
Last edited on
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