[英]Dependency Injection Unity - Conditional Resolving
条件解析是我目前不明白的最后一件事。
假设我们有一个接口IAuthenticate
:
public interface IAuthenticate{
bool Login(string user, string pass);
}
现在我有两种类型的身份验证。
推特认证
public class TwitterAuth : IAuthenticate
{
bool Login(string user, string pass)
{
//connect to twitter api
}
}
脸书认证
public class FacebookAuth: IAuthenticate
{
bool Login(string user, string pass)
{
//connect to fb api
}
}
在统一配置中注册类型:
unityContainer.RegisterType<IAuthenticate, TwitterAuth>();
unityContainer.RegisterType<IAuthenticate, FacebookAuth>();
在我们的控制器中通过 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);
}
unity 究竟如何知道它必须为不同类型的身份验证解析哪个对象? 在这种情况下如何进行条件解析?
我和我的朋友谈过,他解释说,如果出现这种情况,那是设计错误,但这只是使用的工厂模式。
解决这个问题的一个简单方法是使用策略模式。 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。
public interface IAuthenticate{
bool Login(string user, string pass);
bool AppliesTo(string providerName);
}
public interface IAuthenticateStrategy
{
bool Login(string providerName, string user, string pass);
}
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);
}
}
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);
}
}
// 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 ResolvedParameter<IAuthenticate>("facebookAuth")
)
));
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);
}
您可以在您的 unity.config 上执行此操作,而不是“Unity Registration”
<register type="IAuthenticate" mapTo="TwitterAuth" name="twitterAuth" />
<register type="IAuthenticate" mapTo="FacebookAuth" name="facebookAuth" />
<register type="IAuthenticateStrategy" mapTo="AuthenticateStrategy" />
Unity 离不开您的帮助。 您可以在注册 IAuthenticate 类型时提供一个名称:
unityContainer.RegisterType<IAuthenticate, TwitterAuth>("Twitter");
unityContainer.RegisterType<IAuthenticate, FacebookAuth>("Facebook");
您将不再希望将 IAuthenticate 实例直接注入您的 AuthenticateController。 您将根据不统一的条件(服务定位器样式)获得所需的实例:
myContainer.Resolve<IAuthenticate>("Twitter");
或者你会注入一个为你做这件事的工厂(如果你喜欢严格的 DI 风格)。
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