Ninject - 如何以及何时注射 [英] Ninject - how and when to inject

问题描述

我是一个新手，当涉及到DI和ninject，我正在努力一点
关于实际注射应该发生和如何启动
绑定。

我已经在我的网络应用程序中使用它，它的工作正常，
，但现在我想在类库中使用注入。

说我有一个这样的类：

  public class TestClass 
 {
 [Inject] 
 public IRoleRepository RoleRepository {get;组; } 
 [Inject] 
 public ISiteRepository SiteRepository {get;组; } 
 [Inject] 
 public IUserRepository UserRepository {get;组; } 
 
 private readonly string _fileName; 
 
 public TestClass（s​​tring fileName）
 {
 _fileName = fileName; 
} 
 
 public void ImportData（）
 {
 var user = UserRepository.GetByUserName（myname）; 
 var role = RoleRepository.GetByRoleName（myname）; 
 var site = SiteRepository.GetByID（15）; 
 //使用文件等
} 
 
} 
  

我想在这里使用属性注入，因为我需要在我的构造函数中传入一个
文件名。我正确地说，如果我需要
传递一个构造函数参数，我不能使用构造函数注入？
如果我可以使用构造函数注入附加参数，那么
如何传递这些参数？

我有一个控制台应用程序消耗的测试看起来像
的类如下：

  class Program 
 {
 static void Main（string [] args）
 {
 // NinjectRepositoryModule将我的IRoleRepository等绑定到具体的
 //类型，可以正常工作，因为我在我的Web应用程序中使用它任何
 //问题
 IKernel kernel = new StandardKernel（new NinjectRepositoryModule（））; 
 
 var test = new TestClass（filename）; 
 
 test.ImportData（）; 
} 
} 
  

我的问题是当我打电话 test.ImportData（）我的存储库为空 - 没有注入到它们中。我尝试创建另一个模块，并调用

 绑定< TestClass>（）。ToSelf（）; 
  

，因为我以为这可能会解决 TestClass 但我无处可去。

我确定这是一个微不足道的问题，但我似乎找不到
如何

解决方案

您直接新建 TestClass ，其中Ninject没有办法拦截 - 记住没有像代码转换拦截你的新的等等的魔术。

你应该要做 kernel.Get< TestClass> 。

如果没有，你可以在你之后注入 c code code code $ kernel.Inject（test）;

我认为wiki中有一篇关于 Inject vs Get 等的文章。请注意，一般来说，直接获取或注入调用是一个做错了服务位置的气味，这是一个反刍动物燕鸥。在您的网络应用程序的情况下， NinjectHttpModule 和 PageBase 是拦截对象创建的钩子 - 有类似的拦截器/其他样式的应用程序拦截的逻辑位置。

重新使用绑定&TestClass>（）。ToSelf（），通常一个 StandardKernel 有 ImplicitSelfBinding = true 这将使得不必要（除非你想影响其范围是除了 .InTransientScope（）之外的其他东西。

最后的风格点： - 您正在使用属性注入。这很少有很好的理由，所以你应该使用构造函数注入。

并且去买 @Mark Seemann的.NET中的依赖注入，这里有一堆优秀的帖子，涵盖了依赖注入区域及其周围的许多重要而微妙的考虑。

I'm a newbie when it comes to DI and ninject and I'm struggling a bit about when the actual injection should happen and how to start the binding.

I'm using it already in my web application and it working fine there, but now I want to use injection in a class library.

Say I have a class like this:

public class TestClass
{
    [Inject]
    public IRoleRepository RoleRepository { get; set; }
    [Inject]
    public ISiteRepository SiteRepository { get; set; }
    [Inject]
    public IUserRepository UserRepository { get; set; }

    private readonly string _fileName;

    public TestClass(string fileName)
    {
        _fileName = fileName;
    }

    public void ImportData()
    {
        var user = UserRepository.GetByUserName("myname");
        var role = RoleRepository.GetByRoleName("myname");
        var site = SiteRepository.GetByID(15);
        // Use file etc
    }

}

I want to use property injection here because I need to pass in a filename in my constructor. Am I correct in saying that if I need to pass in a constructor parameter, I cannot use constructor injection? If I can use constructor injection with additional parameters, how do I pass those parameters in?

I have a console app that consumes by Test class that looks as follows:

class Program
{
    static void Main(string[] args)
    {
        // NinjectRepositoryModule Binds my IRoleRepository etc to concrete
        // types and works fine as I'm using it in my web app without any
        // problems
        IKernel kernel = new StandardKernel(new NinjectRepositoryModule());

        var test = new TestClass("filename");

        test.ImportData();
    }
}

My problem is that when I call test.ImportData() my repositories are null - nothing has been injected into them. I have tried creating another module and calling

Bind<TestClass>().ToSelf();

as I thought this might resolve all injection properties in TestClass but I'm getting nowhere.

I'm sure this is a trivial problem, but I just can't seem to find out how to go about this.

解决方案

You are directly newing TestClass, which Ninject has no way of intercepting - remember there's no magic like code transformation intercepting your news etc.

You should be doing kernel.Get<TestClass> instead.

Failing that, you can inject it after you new it with a kernel.Inject( test);

I think there's an article in the wiki that talks about Inject vs Get etc.

Note that in general, direct Get or Inject calls are a Doing It Wrong smell of Service Location, which is an antipattern. In the case of your web app, the NinjectHttpModule and PageBase are the hook that intercepts object creation - there are similar interceptors / logical places to intercept in other styles of app.

Re your Bind<TestClass>().ToSelf(), generally a StandardKernel has ImplicitSelfBinding = true which would make that unnecessary (unless you want to influence its Scope to be something other than .InTransientScope()).

A final style point:- you're using property injection. There are rarely good reasons for this, so you should be using constructor injection instead.

And do go buy Dependency Injection in .NET by @Mark Seemann, who has stacks of excellent posts around here which cover lots of important but subtle considerations in and around the Dependency Injection area.

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