model_collection.h

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#pragma once
 
#include <type_traits>
#include <variant>
#include <vector>
 
#include "../io/ParameterMap.h"
#include "../utils/error_handling.h"  // always_false
#include "galaxy/disk_galaxy.h"
 
 
namespace model_detail
{
 
// this is just a placeholder model type until we have 2 or more models
struct DummyModel {
  explicit DummyModel(ParameterMap& pmap) {}
};
 
// a type-safe union that can represent all model types
// -> to add a new kind of model, append it to the list of template arguments
// -> todo: consolidate DiskGalaxy and ClusteredDiskGalaxy into a single class
using model_variant = std::variant<DummyModel, ClusteredDiskGalaxy>;
 
// define logic to check if a type T is an allowed type of a std::variant
template <typename T, typename variant>
struct isVariantAlternativeType;
 
template <typename T, typename... Types>
struct isVariantAlternativeType<T, std::variant<Types...>> : public std::disjunction<std::is_same<T, Types>...> {
};
 
// evaluates to whether a type T is a known variant type
template <class T>
constexpr bool is_model_type = isVariantAlternativeType<T, model_variant>::value;
 
}  // namespace model_detail
 
class ModelCollection
{
  std::vector<model_detail::model_variant> vec_;
 
 public:
  ModelCollection() = default;
 
  explicit ModelCollection(ParameterMap& pmap);
 
  ModelCollection(ModelCollection&&)            = default;
  ModelCollection& operator=(ModelCollection&&) = default;
 
  // we forbid copy construction and copy assignment to retain flexibility (in case
  // we convert vec_ to hold std::unique_ptr instances)
  ModelCollection(const ModelCollection&)            = delete;
  ModelCollection& operator=(const ModelCollection&) = delete;
 
  template <typename T>
  const T* try_get() const
  {
    static_assert(model_detail::is_model_type<T>, "T isn't a known model type");
    for (const model_detail::model_variant& v : vec_) {
      const T* ptr = std::get_if<T>(&v);
      if (ptr != nullptr) return ptr;
    }
 
    return nullptr;
  }
};