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检索实现给定接口的对象列表

interface plugins architecture generics c#

Amirshk · 技术社区 · 15 年前

简介

伊巴塞普卢金 ,或从基本接口继承的某些其他接口:

interface IBasePlugin
interface IMainFormEvents : IBasePlugin

主机正在加载插件程序集,然后为实现插件的任何类创建适当的对象 伊巴塞普卢金 界面

这是加载插件并实例化对象的类:

 public class PluginCore
 {
     #region implement singletone instance of class
     private static PluginCore instance;
     public static PluginCore PluginCoreSingleton
     {
         get
         {
             if (instance == null)
             {
                 instance = new PluginCore();
             }
             return instance;
         }
     }
     #endregion

     private List<Assembly> _PlugInAssemblies = null;
     /// <summary>
     /// Gets the plug in assemblies.
     /// </summary>
     /// <value>The plug in assemblies.</value>
     public List<Assembly> PlugInAssemblies
     {
         get
         {
             if (_PlugInAssemblies != null) return _PlugInAssemblies;

             // Load Plug-In Assemblies
             DirectoryInfo dInfo = new DirectoryInfo(
                 Path.Combine(
                     Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location),
                     "Plugins"
                     )
                 );
             FileInfo[] files = dInfo.GetFiles("*.dll");
             _PlugInAssemblies = new List<Assembly>();
             if (null != files)
             {
                 foreach (FileInfo file in files)
                 {
                     _PlugInAssemblies.Add(Assembly.LoadFile(file.FullName));
                 }
             }

             return _PlugInAssemblies;
         }
     }

     List<IBasePlugin> _pluginsList = null;
     /// <summary>
     /// Gets the plug ins instances.
     /// all the plugins are being instanciated ONCE when this if called for the first time
     /// every other call will return the existing classes.
     /// </summary>
     /// <value>The plug ins instances.</value>
     public List<IBasePlugin> PlugInInstances
     {
         get
         {
             if (_pluginsList != null) return _pluginsList;

             List<Type> availableTypes = new List<Type>();

             foreach (Assembly currentAssembly in this.PlugInAssemblies)
                 availableTypes.AddRange(currentAssembly.GetTypes());

             // get a list of objects that implement the IBasePlugin
             List<Type> pluginsList = availableTypes.FindAll(delegate(Type t)
             {
                 List<Type> interfaceTypes = new List<Type>(t.GetInterfaces());
                 return interfaceTypes.Contains(typeof(IBasePlugin));
             });

             // convert the list of Objects to an instantiated list of IBasePlugin
             _pluginsList = pluginsList.ConvertAll<IBasePlugin>(delegate(Type t) { return Activator.CreateInstance(t) as IBasePlugin; });

             return _pluginsList;
         }
     }

目前,任何支持插件的模块都使用插件属性来检索列表然后,它迭代查询谁正在实现给定子接口的对象。

foreach (IBasePlugin plugin in PluginCore.PluginCoreSingleton.PlugInInstances)
{
     if (plugin is IMainFormEvents)
     {
         // Do something
     }
 }

伪代码:

void GetListByInterface(Type InterfaceType, out List<InterfaceType> Plugins)

您对如何实施这一点有何建议?

3 回复 | 直到 15 年前

Andrew Kennan 15 年前

您可以尝试以下方法:

void GetListByInterface<TInterface>(out IList<TInterface> plugins) where TInterface : IBasePlugin
{
  plugins = (from p in _allPlugins where p is TInterface select (TInterface)p).ToList();
}

John Gietzen 15 年前

您可以在此处查看源代码: http://tournaments.codeplex.com/SourceControl/ListDownloadableCommits.aspx

在trunk/TournamentApi/Plugins/PluginLoader.cs中,我定义了加载任意程序集插件所需的方法。

以下是代码的要点:

List<IPluginFactory> factories = new List<IPluginFactory>();

try
{
    foreach (Type type in assembly.GetTypes())
    {
        IPluginEnumerator instance = null;

        if (type.GetInterface("IPluginEnumerator") != null)
        {
            instance = (IPluginEnumerator)Activator.CreateInstance(type);
        }

        if (instance != null)
        {
            factories.AddRange(instance.EnumerateFactories());
        }
    }
}
catch (SecurityException ex)
{
    throw new LoadPluginsFailureException("Loading of plugins failed.  Check the inner exception for more details.", ex);
}
catch (ReflectionTypeLoadException ex)
{
    throw new LoadPluginsFailureException("Loading of plugins failed.  Check the inner exception for more details.", ex);
}

return factories.AsReadOnly();

Chris Patterson 15 年前

我将使用IOC容器来执行插件查找。MEF可能有点多,但StructureMap是一个单独的DLL,并且内置了对这种开箱即用的支持。

StructureMap on SourceForge

ObjectFactory的Configure方法中的扫描示例:

        Scan(scanner =>
        {
            string assemblyPath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);

            scanner.AssembliesFromPath(assemblyPath, assembly => { return assembly.GetName().Name.StartsWith("Plugin."); });

            scanner.With(typeScanner);
        });

类型扫描程序实现ITypeScanner,并可以检查类型是否可分配给相关接口类型。在所附的文档链接中有一些很好的例子。