如何确保我的类 Initialize 方法只被调用一次，最好的方法是什么？

Question

我目前正在使用 Unity IoC Container，这是我的 AppConfig 类。如您所见，Initialize 方法应该只被调用一次，并且我使用了双重锁检查来确保这一点。

如果我的方法不是最好的方法，那么实现这一目标的最佳方法是什么？

public interface IAppConfig
{
    /// <summary>
    /// Gets the admin username.
    /// </summary>
    /// <value>The admin username.</value>
    string AdminUsername { get; }

    /// <summary>
    /// Gets the admin password.
    /// </summary>
    /// <value>The admin password.</value>
    string AdminPassword { get; }

    /// <summary>
    /// Initializes this instance.
    /// </summary>
    void Initialize();
}

/// <summary>
/// A singleton App config which helps reading from web.config
/// its lifetime is controlled by Unity.
/// </summary>
public class AppConfig : IAppConfig
{
    #region Fields

    /// <summary>
    /// the injectable config manager
    /// </summary>
    private readonly IConfigManager _configManager;

    private readonly ILogger _logger;

    private static readonly object LockObject = new object();

    private static bool _initialized = false;

    #endregion

    #region Constructors

    /// <summary>
    /// Initializes a new instance of the <see cref="AppConfig"/> class.
    /// </summary>
    public AppConfig(IConfigManager configManager, ILogger logger)
    {
        this._configManager = configManager;
        this._logger = logger;
    }

    #endregion

    #region Properties

    /// <summary>
    /// Gets the admin username.
    /// </summary>
    /// <value>The admin username.</value>
    public string AdminUsername { get; private set; }

    /// <summary>
    /// Gets the admin password.
    /// </summary>
    /// <value>The admin password.</value>
    public string AdminPassword { get; private set; }

    #endregion

    #region Methods

    public void Initialize()
    {
        if (_initialized)
        {
            throw new ApplicationException("Initialize method should be called only once");
        }

        lock(LockObject)
        {
            if (_initialized) return;

            var adminUserNameSetting = _configManager.AppSettings[ConfigKeys.AdminUsername];

            if (adminUserNameSetting == null)
            {
                throw new ApplicationException("AdminUsername key not found");
            }

            this.AdminUsername = adminUserNameSetting.Value;

            if (String.IsNullOrWhiteSpace(this.AdminUsername))
            {
                _logger.LogError("AdminUsername not found");
            }

            // log
            var adminPasswordSetting = _configManager.AppSettings[ConfigKeys.AdminPassword];

            if (adminPasswordSetting == null)
            {
                throw new ApplicationException("AdminPassword key not found");
            }

            this.AdminPassword = adminPasswordSetting.Value;

            if (String.IsNullOrWhiteSpace(this.AdminPassword))
            {
                _logger.LogError("AdminPassword not found");
            }
            _initialized = true;
        }
    }

    #endregion
}

在 Unity 中，我使用以下代码：

// IAppConfig
container.RegisterType<IAppConfig, AppConfig>(new ContainerControlledLifetimeManager(),
                                              new InjectionConstructor(configManager,
                                                                       logger));
var appConfig = container.Resolve<IAppConfig>();
appConfig.Initialize();

Answer 1

我认为Initalize() 方法更像是一个实现问题。这意味着它可能根本不应该出现在界面中。

初始化实例最好留给构造函数。

如果您确实需要延迟初始化，那么您使用 bool 和锁的解决方案似乎没问题。

Answer 2

根据您在 Initialize 方法中所做的判断，我认为您需要研究的是将该类注册为单例并持久化容器。您可以在此处查看执行此操作的示例：

http://gunnarpeipman.com/2008/04/unity-and-singletons/

Answer 3

好的，所以您依靠 Unity 来确保您的课程是单例的。尽管 C# 的代码模式非常简单。见here。然后在构造函数中调用初始化代码。

在任何情况下，我都会将您的初始化标志声明为 volatile，因为代码是 atmo。

Answer 4

我更喜欢有一个静态类实例变量来检查它是否已在 get 访问器中初始化。通过实例属性访问该类，您将控制该类的初始化次数。这几乎是默认的 C# 单例模式：

public static class MySingleton 
{
    private static Mutex instanceLock = new Mutex();

    private static MySingleton instance;
    public static MySingleton Instance
    {
        get
        {
            instanceLock.WaitOne();
            if(instance == null)
            {
                instance = new MySingleton();
            }
            instanceLock.ReleaseMutex();
            return instance;
         }
    }

    private MySingleton()
    {
        Initialize();
    }

    private void Initialize()
    {
        // Initialize
    }
}

public class MyOtherClass
{
    private MySingleton singleton = MySingleton.Instance;
}