Am I abusing Policies?
- by pmr
I find myself using policies a lot in my code and usually I'm very happy with that.
But from time to time I find myself confronted with using that pattern in situations where the Policies are selected and runtime and I have developed habbits to work around such situations. Usually I start with something like that:
class DrawArrays {
protected:
void sendDraw() const;
};
class DrawElements {
protected:
void sendDraw() const;
};
template<class Policy>
class Vertices : public Policy {
using Policy::sendDraw();
public:
void render() const;
};
When the policy is picked at runtime I have different choices of working around the situation.
Different code paths:
if(drawElements) {
Vertices<DrawElements> vertices;
} else {
Vertices<DrawArrays> vertices;
}
Inheritance and virtual calls:
class PureVertices {
public:
void render()=0;
};
template<class Policy>
class Vertices : public PureVertices, public Policy {
//..
};
Both solutions feel wrong to me. The first creates an umaintainable mess and the second introduces the overhead of virtual calls that I tried to avoid by using policies in the first place.
Am I missing the proper solutions or do I use the wrong pattern to solve the problem?
