我有以下类和接口结构,并且我很难尝试让代码执行我需要的操作。
public interface IUserManager
{
int Add(User user);
}
public class UserManagerA : IUserManager{}
public class UserManagerB : IUserManager{}
在此示例中,我使用 Ninject 作为 IoC 容器,但如果其他容器解决了问题,我愿意更改它:
这是我里面的NinjectWebCommon.cs
:
void RegisterServices(IKernel kernel)
{
string userRole = CurrentUser.Role;//this gets the user logged in
//This is the part I do not how to do
//I wish I could just type this in:
kernel.Bind<IUserManager>().To<UserManagerA>()
.When(userRole == "RoleA"); // this doesn't work obviously
kernel.Bind<IUserManager>().To<UserManagerB>()
.When(userRole == "RoleB"); // same doesn't work
}
所有这些,以便在我的 (MVC) 控制器中我可以执行以下操作:
public class UserController
{
private readonly IUserManager _userManager;
public UserController(IUserManager userManager)
{
_userManager = userManager;
}
public ActionResult Add(User user)
{
//this would call the correct manager
//based on the userRole
_userManager.Add(user);
}
}
我一直在阅读有关抽象工厂的文章,但没有找到一篇解释如何将工厂与 IoC 容器集成并传递在运行时获取的参数来解析实现的文章。
创建一个类负责提供正确的UserManager
并将其注入到您的控制器中:
public class UserManagerProvider : IUserManagerProvider
{
private readonly IContext _context;
public UserManagerProvider(IContext context)
{
_context = context;
}
public IUserManager Create(User currentUser)
{
if (currentUser.Role == "User A")
return _context.Kernel.Get<UserManagerA>();
if (currentUser.Role == "User B")
return _context.Kernel.Get<UserManagerB>();
// Or bind and resolve by name
// _context.Kernel.Get<IUserManager>(currentUser.Role);
}
}
在控制器中:
private readonly IUserManager _userManager;
public UserController(IUserManagerProvider userManagerProvider)
{
_userManager = userManagerProvider.Create(CurrentUser);
}
另外,作为旁注,您可能应该有一个CurrentUserProvider
负责获取当前用户。依赖静态方法将使单元测试变得困难,并且您实际上隐藏了引用它的所有类中的依赖项:
private readonly IUserManager _userManager;
private readonly User _currentUser;
public UserController(IUserManagerProvider userManagerProvider, ICurrentUserProvider currentUserProvider)
{
_currentUser = currentUserProvider.GetUser();
_userManager = userManagerProvider.Create(_currentUser);
}
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