Add static creation method for ConfigManager

Author: trflynn89

fly/config/config_manager.cpp

@@ -11,14 +11,40 @@
 
 namespace fly {
 
+//==================================================================================================
+std::shared_ptr<ConfigManager> ConfigManager::create(
+    std::shared_ptr<SequencedTaskRunner> task_runner,
+    ConfigFileType file_type,
+    std::filesystem::path path)
+{
+    // ConfigManager has a private constructor, thus cannot be used with std::make_shared. This
+    // class is used to expose the private constructor locally.
+    struct ConfigManagerImpl final : public ConfigManager
+    {
+        ConfigManagerImpl(
+            std::shared_ptr<SequencedTaskRunner> task_runner,
+            ConfigFileType file_type,
+            std::filesystem::path path) noexcept :
+            ConfigManager(std::move(task_runner), file_type, std::move(path))
+        {
+        }
+    };
+
+    auto config_manager =
+        std::make_shared<ConfigManagerImpl>(std::move(task_runner), file_type, std::move(path));
+    return config_manager->start() ? config_manager : nullptr;
+}
+
 //==================================================================================================
 ConfigManager::ConfigManager(
-    const std::shared_ptr<SequencedTaskRunner> &task_runner,
+    std::shared_ptr<SequencedTaskRunner> task_runner,
     ConfigFileType file_type,
-    const std::filesystem::path &path) noexcept :
-    m_path(path),
-    m_task_runner(task_runner)
+    std::filesystem::path path) noexcept :
+    m_task_runner(std::move(task_runner)),
+    m_path(std::move(path))
 {
+    m_monitor = std::make_shared<PathMonitorImpl>(m_task_runner, create_config<PathConfig>());
+
     switch (file_type)
     {
         case ConfigFileType::Ini:
@@ -47,35 +73,27 @@ ConfigManager::~ConfigManager()
 //==================================================================================================
 bool ConfigManager::start()
 {
-    if (m_parser)
+    if (!m_parser || !m_monitor)
     {
-        m_monitor = std::make_shared<PathMonitorImpl>(m_task_runner, create_config<PathConfig>());
+        return false;
+    }
 
-        if (m_monitor->start())
-        {
-            std::weak_ptr<ConfigManager> weak_self = shared_from_this();
+    std::weak_ptr<ConfigManager> weak_self = shared_from_this();
 
-            auto callback = [weak_self](const std::filesystem::path &, PathMonitor::PathEvent)
+    auto callback = [weak_self](std::filesystem::path, PathMonitor::PathEvent)
+    {
+        if (auto self = weak_self.lock(); self)
+        {
+            auto task = [](std::shared_ptr<ConfigManager> nested_self)
             {
-                if (auto self = weak_self.lock(); self)
-                {
-                    auto task = [](std::shared_ptr<ConfigManager> nested_self)
-                    {
-                        nested_self->update_config();
-                    };
-
-                    self->m_task_runner->post_task(
-                        FROM_HERE,
-                        std::move(task),
-                        std::move(weak_self));
-                }
+                nested_self->update_config();
             };
 
-            return m_monitor->add_file(m_path, callback);
+            self->m_task_runner->post_task(FROM_HERE, std::move(task), std::move(weak_self));
         }
-    }
+    };
 
-    return false;
+    return m_monitor->add_file(m_path, callback);
 }
 
 //==================================================================================================

fly/config/config_manager.hpp

@@ -42,29 +42,24 @@ class ConfigManager : public std::enable_shared_from_this<ConfigManager>
     };
 
     /**
-     * Constructor.
+     * Create and start a configuration manager.
      *
      * @param task_runner Task runner for posting config-related tasks onto.
      * @param file_type File format of the configuration file.
      * @param path Path to the configuration file.
+     *
+     * @return The created configuration manager.
      */
-    ConfigManager(
-        const std::shared_ptr<SequencedTaskRunner> &task_runner,
+    static std::shared_ptr<ConfigManager> create(
+        std::shared_ptr<SequencedTaskRunner> task_runner,
         ConfigFileType file_type,
-        const std::filesystem::path &path) noexcept;
+        std::filesystem::path path);
 
     /**
      * Destructor. Stop the configuration manager and underlying objects.
      */
     ~ConfigManager();
 
-    /**
-     * Start the configuration manager and underlying objects.
-     *
-     * @return True if the manager could be started.
-     */
-    bool start();
-
     /**
      * Create a configuration object, or if one with the given type's name exists, fetch it.
      *
@@ -83,19 +78,38 @@ class ConfigManager : public std::enable_shared_from_this<ConfigManager>
     ConfigMap::size_type prune();
 
 private:
+    /**
+     * Constructor.
+     *
+     * @param task_runner Task runner for posting config-related tasks onto.
+     * @param file_type File format of the configuration file.
+     * @param path Path to the configuration file.
+     */
+    ConfigManager(
+        std::shared_ptr<SequencedTaskRunner> task_runner,
+        ConfigFileType file_type,
+        std::filesystem::path path) noexcept;
+
+    /**
+     * Start the configuration manager and underlying objects.
+     *
+     * @return True if the manager could be started.
+     */
+    bool start();
+
     /**
      * Parse the configuration file and store the parsed values in memory.
      */
     void update_config();
 
+    std::shared_ptr<SequencedTaskRunner> m_task_runner;
+
     std::shared_ptr<PathMonitor> m_monitor;
     std::unique_ptr<Parser> m_parser;
     Json m_values;
 
     const std::filesystem::path m_path;
 
-    std::shared_ptr<SequencedTaskRunner> m_task_runner;
-
     mutable std::mutex m_configs_mutex;
     ConfigMap m_configs;
 };

test/config/config_manager.cpp

@@ -53,37 +53,37 @@ CATCH_TEST_CASE("ConfigManager", "[config]")
     fly::test::PathUtil::ScopedTempDirectory config_path;
     std::filesystem::path config_file = config_path.file();
 
-    auto config_manager = std::make_shared<fly::ConfigManager>(
+    auto config_manager = fly::ConfigManager::create(
         task_runner,
         fly::ConfigManager::ConfigFileType::Json,
         config_file);
-    auto path_config = config_manager->create_config<TestPathConfig>();
-    CATCH_REQUIRE(config_manager->start());
+    CATCH_REQUIRE(config_manager);
 
+    auto path_config = config_manager->create_config<TestPathConfig>();
     auto initial_size = config_manager->prune();
 
     CATCH_SECTION("Config managers can be started for all file types")
     {
-        config_manager = std::make_shared<fly::ConfigManager>(
+        config_manager = fly::ConfigManager::create(
             task_runner,
             fly::ConfigManager::ConfigFileType::Ini,
             config_file);
-        CATCH_CHECK(config_manager->start());
+        CATCH_CHECK(config_manager);
 
-        config_manager = std::make_shared<fly::ConfigManager>(
+        config_manager = fly::ConfigManager::create(
             task_runner,
             fly::ConfigManager::ConfigFileType::Json,
             config_file);
-        CATCH_CHECK(config_manager->start());
+        CATCH_CHECK(config_manager);
     }
 
     CATCH_SECTION("Cannot start a config manager of an unsupported file type")
     {
-        config_manager = std::make_shared<fly::ConfigManager>(
+        config_manager = fly::ConfigManager::create(
             task_runner,
             static_cast<fly::ConfigManager::ConfigFileType>(-1),
             config_file);
-        CATCH_CHECK_FALSE(config_manager->start());
+        CATCH_CHECK_FALSE(config_manager);
     }
 
     CATCH_SECTION("Cannot create a config with a duplicated identifier")