我使用依赖注入(inject) (DI) 和 Ninject 作为 DI 容器创建了一个 WinForms MVC 应用程序。基本架构如下
Program.cs(WinForms 应用程序的主要入口点):
static class Program
{
[STAThread]
static void Main()
{
...
CompositionRoot.Initialize(new DependencyModule());
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(CompositionRoot.Resolve<ApplicationShellView>());
}
}
DependencyModule.cs
public class DependencyModule : NinjectModule
{
public override void Load()
{
Bind<IApplicationShellView>().To<ApplicationShellView>();
Bind<IDocumentController>().To<SpreadsheetController>();
Bind<ISpreadsheetView>().To<SpreadsheetView>();
}
}
CompositionRoot.cs
public class CompositionRoot
{
private static IKernel ninjectKernel;
public static void Initialize(INinjectModule module)
{
ninjectKernel = new StandardKernel(module);
}
public static T Resolve<T>()
{
return ninjectKernel.Get<T>();
}
public static IEnumerable<T> ResolveAll<T>()
{
return ninjectKernel.GetAll<T>();
}
}
ApplicationShellView.cs(应用程序的主要形式)
public partial class ApplicationShellView : C1RibbonForm, IApplicationShellView
{
private ApplicationShellController controller;
public ApplicationShellView()
{
this.controller = new ApplicationShellController(this);
InitializeComponent();
}
public void InitializeView()
{
dockPanel.Extender.FloatWindowFactory = new CustomFloatWindowFactory();
dockPanel.Theme = vS2012LightTheme;
}
private void ribbonButtonTest_Click(object sender, EventArgs e)
{
controller.OpenNewSpreadsheet();
}
public DockPanel DockPanel
{
get { return dockPanel; }
}
}
在哪里
public interface IApplicationShellView
{
void InitializeView();
DockPanel DockPanel { get; }
}
ApplicationShellController.cs
public class ApplicationShellController
{
private IApplicationShellView shellView;
public ApplicationShellController(IApplicationShellView view)
{
this.shellView = view;
}
public void OpenNewSpreadsheet(DockState dockState = DockState.Document)
{
SpreadsheetController controller = (SpreadsheetController)GetDocumentController("new.xlsx");
SpreadsheetView view = (SpreadsheetView)controller.New("new.xlsx");
view.Show(shellView.DockPanel, dockState);
}
private IDocumentController GetDocumentController(string path)
{
return CompositionRoot.ResolveAll<IDocumentController>()
.SingleOrDefault(provider => provider.Handles(path));
}
public IApplicationShellView ShellView { get { return shellView; } }
}
SpreadsheetController.cs
public class SpreadsheetController : IDocumentController
{
private ISpreadsheetView view;
public SpreadsheetController(ISpreadsheetView view)
{
this.view = view;
this.view.SetController(this);
}
public bool Handles(string path)
{
string extension = Path.GetExtension(path);
if (!String.IsNullOrEmpty(extension))
{
if (FileTypes.Any(ft => ft.FileExtension.CompareNoCase(extension)))
return true;
}
return false;
}
public void SetViewActive(bool isActive)
{
((SpreadsheetView)view).ShowIcon = isActive;
}
public IDocumentView New(string fileName)
{
// Opens a new file correctly.
}
public IDocumentView Open(string path)
{
// Opens an Excel file correctly.
}
public IEnumerable<DocumentFileType> FileTypes
{
get
{
return new List<DocumentFileType>()
{
new DocumentFileType("CSV", ".csv" ),
new DocumentFileType("Excel", ".xls"),
new DocumentFileType("Excel10", ".xlsx")
};
}
}
}
实现的接口(interface)在哪里
public interface IDocumentController
{
bool Handles(string path);
void SetViewActive(bool isActive);
IDocumentView New(string fileName);
IDocumentView Open(string path);
IEnumerable<DocumentFileType> FileTypes { get; }
}
现在与这个 Controller 关联的 View 是
public partial class SpreadsheetView : DockContent, ISpreadsheetView
{
private IDocumentController controller;
public SpreadsheetView()
{
InitializeComponent();
}
private void SpreadsheetView_Activated(object sender, EventArgs e)
{
controller.SetViewActive(true);
}
private void SpreadsheetView_Deactivate(object sender, EventArgs e)
{
controller.SetViewActive(false);
}
public void SetController(IDocumentController controller)
{
this.controller = controller;
Log.Trace("SpreadsheetView.SetController(): Controller set successfully");
}
public string DisplayName
{
get { return Text; }
set { Text = value; }
}
public WorkbookView WorkbookView
{
get { return workbookView; }
set { workbookView = value; }
}
...
}
最后是 View 界面
public interface ISpreadsheetView : IDocumentView
{
WorkbookView WorkbookView { get; set; }
}
和
public interface IDocumentView
{
void SetController(IDocumentController controller);
string DisplayName { get; set; }
bool StatusBarVisible { get; set; }
}
现在是我的问题。在 Seemann 的书“.NET 中的依赖注入(inject)”中,他谈到了“三次调用模式”,这就是我在上面试图实现的。代码有效,shell View 显示并通过 MVC 模式我的 Controller 正确打开 View 等。但是,我很困惑,因为上面肯定有“服务定位器反模式”的味道。在 Seemann 的书的第 3 章中,他说
The COMPOSITION ROOT pattern describes where you should use a DI CONTAINER. However, it doesn’t state how to use it. The REGISTER RESOLVE RELEASE pattern addresses this question [...] A DI CONTAINER should be used in three successive phases called Register, Resolve, and Release.
In its pure form, the REGISTER RESOLVE RELEASE pattern states that you should only make a single method call in each phase. Krzysztof Kozimic calls this the Three Calls Pattern.
Configuring a DI CONTAINER in a single method call requires more explanation. The reason that registration of components should happen in a single method call is because you should regard configuration of a DI CONTAINER as a single, atomic action. Once configuration is completed, the container should be regarded as read-only.
这听起来像是被挖出的“服务定位器”,为什么这不被视为服务位置?
为了调整我的代码以使用 Contstructor Injection,我将入口代码更改为
[STAThread]
static void Main()
{
var kernel = new StandardKernel();
kernel.Bind(t => t.FromThisAssembly()
.SelectAllClasses()
.BindAllInterfaces());
FileLogHandler fileLogHandler = new FileLogHandler(Utils.GetLogFilePath());
Log.LogHandler = fileLogHandler;
Log.Trace("Program.Main(): Logging initialized");
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(kernel.Get<ApplicationShellView>());
}
使用 Ninject.Extensions.Conventions
,然后我更改了ApplicationShellController
为了更正我的代码以注入(inject) IDocumentController
s 通过 ctor 注入(inject):
public class ApplicationShellController
{
private IApplicationShellView shellView;
private IEnumerable<IDocumentController> controllers;
public ApplicationShellController(IApplicationShellView shellView, IEnumerable<IDocumentController> controllers)
{
this.shellView = shellView;
this.controllers = controllers;
Log.Trace("ApplicationShellController.Ctor(): Shell initialized successfully");
}
...
}
在哪里
public class SpreadsheetController : IDocumentController
{
private ISpreadsheetView view;
public SpreadsheetController(ISpreadsheetView view)
{
this.view = view;
this.view.SetController(this);
}
...
}
但这会导致循环依赖,我该如何处理呢?
问题总结:
- 为什么我最初使用 Ninject 使用“Thee Calls Pattern”和
CompositionRoot.Resolve<T>()
服务定位器反模式不好或不同? - 如果我想切换到纯 ctor 注入(inject),如何解决上述循环依赖问题?
非常感谢您的宝贵时间。
最佳答案
在流程的某个时刻,您必须使用服务位置。然而,DI 和 SL 之间的区别在于,在 SL 中,您在请求它们时解析您的服务,而在 DI 中,您在某种工厂(例如 Controller 工厂)中解析它们,然后构造您的对象并通过中的引用。
您应该创建某种基础设施来分派(dispatch)您的命令并使用某种工厂来定位所创建对象所使用的依赖项。
通过这种方式,您的其余代码没有依赖项解析,并且除了构造点外,您都遵循 DI 模式。
关于c# - Seemann 依赖注入(inject), "Three Calls Pattern"与服务定位器反模式,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/35895538/