依赖注入统一 - 条件解析

Question

条件解决是目前我​​还不了解的最后一件事。

假设我们有一个界面IAuthenticate：

public interface IAuthenticate{
    bool Login(string user, string pass);
}

现在我有两种类型的身份验证。

Twitter身份验证

public class TwitterAuth : IAuthenticate
{
  bool Login(string user, string pass)
{
   //connect to twitter api
}

}

Facebook Auth

public class FacebookAuth: IAuthenticate
{
  bool Login(string user, string pass)
{
   //connect to fb api
}

}

在unity config中注册类型：

unityContainer.RegisterType<IAuthenticate, TwitterAuth>();
unityContainer.RegisterType<IAuthenticate, FacebookAuth>();

在控制器中通过DI注入对象：

private readonly IAuthenticate _authenticate;

public AuthenticateController(IAuthenticate authenticate)
{
    _authenticate = authenticate;
}



// login with twitter
public virtual ActionResult Twitter(string user, string pass)
{
    bool success =
            _authenticate.Login(user, pass);
}



// login with fb
public virtual ActionResult Facebook(string user, string pass)
{
    bool success =
            _authenticate.Login(user, pass);
}



// login with google
public virtual ActionResult Google(string user, string pass)
{
    bool success =
            _authenticate.Login(user, pass);
}

对于不同类型的身份验证，Unity统一知道它必须解决哪个对象？在这种情况下如何进行条件解决？

我和我的朋友谈过，他解释说如果这种情况出现是错误的设计，但这只是工厂模式使用。

Answer 1

解决此问题的一种简单方法是使用strategy pattern。请注意，您可以在不更改设计的情况下添加或删除登录提供程序 - 您只需更改DI配置。

接口

public interface IAuthenticate{
    bool Login(string user, string pass);
    bool AppliesTo(string providerName);
}

public interface IAuthenticateStrategy
{
    bool Login(string providerName, string user, string pass);
}

验证提供商

public class TwitterAuth : IAuthenticate
{
    bool Login(string user, string pass)
    {
        //connect to twitter api
    }

    bool AppliesTo(string providerName)
    {
        // I used the type name for this example, but
        // note that you could use any string or other
        // datatype to select the correct provider.
        return this.GetType().Name.Equals(providerName);
    }
}

public class FacebookAuth: IAuthenticate
{
    bool Login(string user, string pass)
    {
        //connect to fb api
    }

    bool AppliesTo(string providerName)
    {
        return this.GetType().Name.Equals(providerName);
    }
}

策略

public class AuthenticateStrategy: IAuthenticateStrategy
{
    private readonly IAuthenticate[] authenticateProviders;

    public AuthenticateStrategy(IAuthenticate[] authenticateProviders)
    {
        if (authenticateProviders == null)
            throw new ArgumentNullException("authenticateProviders");

        this.authenticateProviders = authenticateProviders;
    }

    public bool Login(string providerName, string user, string pass)
    {
        var provider = this.authenticateProviders
            .FirstOrDefault(x => x.AppliesTo(providerName));

        if (provider == null)
        {
            throw new Exception("Login provider not registered");
        }

        return provider.Login(user, pass);
    }
}

Unity注册

// Note that the strings used here for instance names have nothing 
// to do with the strings used to select the instance in the strategy pattern
unityContainer.RegisterType<IAuthenticate, TwitterAuth>("twitterAuth");
unityContainer.RegisterType<IAuthenticate, FacebookAuth>("facebookAuth");
unityContainer.RegisterType<IAuthenticateStrategy, AuthenticateStrategy>(
    new InjectionConstructor(
        new ResolvedArrayParameter<IAuthenticate>(
            new ResolvedParameter<IAuthenticate>("twitterAuth")
        ),
        new ResolvedArrayParameter<IAuthenticate>(
            new ResolvedParameter<IAuthenticate>("facebookAuth")
        )
    ));

用法

private readonly IAuthenticateStrategy _authenticateStrategy;

public AuthenticateController(IAuthenticateStrategy authenticateStrategy)
{
    if (authenticateStrategy == null)
        throw new ArgumentNullException("authenticateStrategy");

    _authenticateStrategy = authenticateStrategy;
}



// login with twitter
public virtual ActionResult Twitter(string user, string pass)
{
    bool success =
            _authenticateStrategy.Login("TwitterAuth", user, pass);
}



// login with fb
public virtual ActionResult Facebook(string user, string pass)
{
    bool success =
            _authenticateStrategy.Login("FacebookAuth", user, pass);
}

Answer 2

Unity没有你的帮助。您可以在注册IAuthenticate类型时提供名称：

unityContainer.RegisterType<IAuthenticate, TwitterAuth>("Twitter");
unityContainer.RegisterType<IAuthenticate, FacebookAuth>("Facebook");

您将不再希望将IAuthenticate实例直接注入AuthenticateController。你可以根据一个条件（服务定位器样式）得到你想要的实例：

myContainer.Resolve<IAuthenticate>("Twitter");

或者您将注入一个为您执行此操作的工厂（如果您喜欢严格的DI样式）。