react-native/ReactCommon/fabric/uimanager/ContextContainer.h

// Copyright (c) Facebook, Inc. and its affiliates.

// This source code is licensed under the MIT license found in the
// LICENSE file in the root directory of this source tree.

#pragma once

#include <memory>
#include <mutex>
#include <string>
#include <typeindex>
#include <typeinfo>
#include <unordered_map>
#include <utility>

namespace facebook {
namespace react {

class ContextContainer;

using SharedContextContainer = std::shared_ptr<ContextContainer>;

/*
 * General purpose dependecy injection container.
 * Instance types must be copyable.
 */
class ContextContainer final {
 public:
  /*
   * Registers an instance of the particular type `T` in the container.
   * If `key` parameter is specified, the instance is registered
   * by `{type, key}` pair.
   */
  template <typename T>
  void registerInstance(const T &instance, const std::string &key = {}) {
    std::lock_guard<std::mutex> lock(mutex_);

    instances_.insert(
        {{std::type_index(typeid(T)), key}, std::make_shared<T>(instance)});
  }

  /*
   * Returns a previously registered instance of the particular type `T`.
   * If `key` parameter is specified, the lookup will be performed
   * by {type, key} pair.
   */
  template <typename T>
  T getInstance(const std::string &key = {}) const {
    std::lock_guard<std::mutex> lock(mutex_);

    return *std::static_pointer_cast<T>(
        instances_.at({std::type_index(typeid(T)), key}));
  }

 private:
  std::unordered_map<
      std::pair<std::type_index, std::string>,
      std::shared_ptr<void>>
      instances_;

  mutable std::mutex mutex_;
};

} // namespace react
} // namespace facebook