[英]How to pass an object type to call a generic method
我的通用方法是这样
public static class AppContainerInstaller
{
public static IMessageHandler<T> Resolve<T>()
{
return _container.Resolve<IMessageHandler<T>>();
}
}
我试图从另一个类中调用此通用方法
public static string ProcessMessage(IMessage message)
{
messageHandler = AppContainerInstaller.Resolve<message.GetType()>();
// THe previous line throws an error.
return messageHandler.Handle(message);
}
谁能告诉我如何将消息类型传递给通用方法?
您必须这样做:
messageHandler = AppContainerInstaller.Resolve<IMessage>();
Resolve
方法是应该在T中传递类型的方法。您看到,使用泛型时,必须提供一个实际的类型。您可能想更改Resolve
以获取T参数,以便传递message
。 像这样:
public static IMessageHandler<T> Resolve<T>(T param)
您这样称呼它:
messageHandler = AppContainerInstaller.Resolve<IMessage>(message);
有两种获取运行时类型的方法:将消息作为参数传递或使用反射。
修改方法:
public static IMessageHandler<T> Resolve<T>(T unused)
{
return _container.Resolve<IMessageHandler<T>>();
}
这将允许运行时类型查找:
// Cast to dynamic to force runtime type
messageHandler = AppContainerInstaller.Resolve((dynamic) message);
您也可以使用反射,尽管这会降低性能。
private static readonly MethodInfo ResolveMethodInfo
= typeof(AppContainerInstaller).GetMethod("Resolve", BindingFlags.Public | BindingFlags.Static);
// Assuming there exists a non-generic interface IMessageHandler
private readonly ConcurrentDictionary<Type, Func<IMessageHandler>> _methodCache
= new ConcurrentDictionary<Type, Func<IMessageHandler>>();
public static string ProcessMessage(IMessage message)
{
messageHandler = Resolve(message.GetType());
return messageHandler.Handle(message);
}
private IMessageHandler Resolve(Type type)
{
// Cache the generated method to avoid repeated reflection penalty.
var resolve = _methodCache.GetOrAdd(type, () => ResolveMethodInfo.MakeGenericMethod(type));
return resolve();
}
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