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https://github.com/zhigang1992/react-native.git
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718ffe5038
Summary: Sometimes we don't know for sure if `ContextContainer` has a value or not (and that's perfectly legit use case). In those cases now we can use `findInstance` method that returns an optional intead of throwing an exeption. Reviewed By: JoshuaGross Differential Revision: D15039137 fbshipit-source-id: 95ba8cc7b76e37d1bd17e18c0098e56350ff3fef
101 lines
3.0 KiB
C++
101 lines
3.0 KiB
C++
// Copyright (c) Facebook, Inc. and its affiliates.
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// This source code is licensed under the MIT license found in the
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// LICENSE file in the root directory of this source tree.
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#pragma once
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#include <memory>
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#include <mutex>
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#include <string>
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#include <better/map.h>
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#include <better/mutex.h>
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#include <better/optional.h>
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namespace facebook {
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namespace react {
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/*
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* General purpose dependecy injection container.
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* Instance types must be copyable.
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*/
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class ContextContainer final {
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public:
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using Shared = std::shared_ptr<ContextContainer const>;
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/*
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* Registers an instance of the particular type `T` in the container
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* using the provided `key`. Only one instance can be registered per key.
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*
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* Convention is to use the plain base class name for the key, so for
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* example if the type `T` is `std::shared_ptr<const ReactNativeConfig>`,
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* then one would use `"ReactNativeConfig"` for the `key`, even if the
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* instance is actually a `shared_ptr` of derived class
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*`EmptyReactNativeConfig`.
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*/
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template <typename T>
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void registerInstance(T const &instance, std::string const &key) const {
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std::unique_lock<better::shared_mutex> lock(mutex_);
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assert(
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instances_.find(key) == instances_.end() &&
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"ContextContainer already had instance for given key.");
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instances_.insert({key, std::make_shared<T>(instance)});
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#ifndef NDEBUG
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typeHashes_.insert({key, typeid(T).hash_code()});
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#endif
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}
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/*
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* Returns a previously registered instance of the particular type `T`
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* for `key`.
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* Throws an exception if the instance could not be found.
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*/
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template <typename T>
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T getInstance(std::string const &key) const {
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std::shared_lock<better::shared_mutex> lock(mutex_);
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assert(
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instances_.find(key) != instances_.end() &&
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"ContextContainer doesn't have an instance for given key.");
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assert(
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typeHashes_.at(key) == typeid(T).hash_code() &&
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"ContextContainer stores an instance of different type for given key.");
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return *std::static_pointer_cast<T>(instances_.at(key));
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}
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/*
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* Returns a (wrapped in an optional) previously registered instance of
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* the particular type `T` for given `key`.
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* Returns an empty optional if the instance could not be found.
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*/
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template <typename T>
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better::optional<T> findInstance(std::string const &key) const {
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std::shared_lock<better::shared_mutex> lock(mutex_);
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auto iterator = instances_.find(key);
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if (iterator == instances_.end()) {
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return {};
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}
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assert(
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typeHashes_.at(key) == typeid(T).hash_code() &&
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"ContextContainer stores an instance of different type for given key.");
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return *std::static_pointer_cast<T>(iterator->second);
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}
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private:
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mutable better::shared_mutex mutex_;
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// Protected by mutex_`.
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mutable better::map<std::string, std::shared_ptr<void>> instances_;
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#ifndef NDEBUG
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mutable better::map<std::string, size_t> typeHashes_;
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#endif
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};
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} // namespace react
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} // namespace facebook
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