factory.h

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#ifndef SINGA_UTILS_FACTORY_H_
#define SINGA_UTILS_FACTORY_H_

#include <glog/logging.h>
#include <functional>
#include <map>
#include <string>

#define CreateInstance(SubClass, BaseClass) \
  [](void)->BaseClass* {return new SubClass();}

template<typename T>
class Factory {
 public:
  inline void Register(const std::string& id,
                       const std::function<T*(void)>& func) {
    CHECK(str2func_.find(id) == str2func_.end())
      << "The id has been registered by another function";
    str2func_[id] = func;
  }
  inline void Register(int id,
                       const std::function<T*(void)>& func) {
    CHECK(id2func_.find(id) == id2func_.end())
      << "The id has been registered by another function";
    id2func_[id] = func;
  }
  inline T* Create(const std::string& id) {
    CHECK(str2func_.find(id) != str2func_.end())
      << "The creation function for " << id << " has not been registered";
    return str2func_[id]();
  }
  inline T* Create(int id) {
    CHECK(id2func_.find(id) != id2func_.end())
      << "The creation function for " << id << " has not been registered";
    return id2func_[id]();
  }

 private:
  // Map that stores the registered creation functions
  std::map<std::string, std::function<T*(void)>> str2func_;
  std::map<int, std::function<T*(void)>> id2func_;
};

#endif  // SINGA_UTILS_FACTORY_H_