Question

I writing an “Effect” class (for an opengl program) and I’m also attempting to write a container class for.

The Effect class is defined as follows:

template <typename T>
class Effect
{
  private:
  Vbo<T>  m_Vbo;
};

Where T is a type that describes the vertex attributes.

In order to write a container class, I’d like to store these effects in an std::map:

class EffectMgr : public Singleton <EffectMgr>
{
private:
    typedef std::map<std::string, Effect<T> & > EffectMap;
};

The error I get with the container class is that T is undefined. Can someone enlighten me?

I may have (by sheer chance and tinkering) have found the answer although I won’t know until I’ve written the container class:

class EffectMgr : public Singleton <EffectMgr>,
{
private:
    template <typename T> 
    typedef std::map<std::string, Effect<T> & > EffectMap;
};

Answer 1

T is scoped within the Effect definition. Outside of the scope T is undefined.

Perhaps you mean this?

template <typename T>
class EffectMgr : public Singleton <EffectMgr>
{
private:
    typedef std::map<std::string, Effect<T> & > EffectMap;
};
// use: EffectMgr<type>::EffectMap

If you want only the typedef to be templated then do this:

class EffectMgr : public Singleton <EffectMgr>
{
private:
    template <typename T>
    using EffectMap = std::map<std::string, Effect<T> & >; // C++11 feature
};
// use: EffectMgr::EffectMap<type>