与ninject循环依赖 [英] Cyclic dependency with ninject

问题描述

我试图找出如何绑定像这样与ninject正确的方法。

I'm trying to figure out correct way how to bind something like this with ninject.

interface IMainService
{
    void DoStuff();
}

interface IOtherService
{
    void DoSomeMagic();
}

abstract class BaseClass
{
    //many stuff here
}

class MainClass : BaseClass, IMainService
{
    public MainClass(IOtherService s)
    {
    }

    public void DoStuff()
    {
        throw new NotImplementedException();
    }

    //do many other things
}

class OtherClass : IOtherService
{
    public OtherClass(IMainService s)
    {
    }

    public void DoSomeMagic()
    {
        throw new NotImplementedException();
    }
}

class BaseModule : NinjectModule
{
    public override void Load()
    {
        Bind<MainClass>().To<MainClass>();
        Bind<IMainService>().To<MainClass>();
        Bind<IOtherService>().To<OtherClass>();
    }
}

static class Program
{
    static void Main()
    {
        var kernel = new StandardKernel(new BaseModule());
        var main = kernel.Get<MainClass>();
    }
}

这让我异常：

It gives me exception:

Error activating IOtherService using binding from IOtherService to OtherClass
A cyclical dependency was detected between the constructors of two services.

Activation path:
  4) Injection of dependency IOtherService into parameter s of constructor of type MainClass
  3) Injection of dependency IMainService into parameter s of constructor of type OtherClass
  2) Injection of dependency IOtherService into parameter s of constructor of type MainClass
  1) Request for MainClass

Suggestions:
  1) Ensure that you have not declared a dependency for IOtherService on any implementations of the service.
  2) Consider combining the services into a single one to remove the cycle.
  3) Use property injection instead of constructor injection, and implement IInitializable if you need initialization logic to be run after property values have been injected.

我不知道怎么写BaseModule。我需要MainClass只有一个实例和OtherClass（如单身）的一个实例。

I don't know how to write BaseModule. I need only one instance of MainClass and one instance of OtherClass (like singletons).

我试过这样的事情：

Bind<MainClass>().To<MainClass>().InSingletonScope();
Bind<IMainService>().To<MainClass>().InRequestScope();
Bind<IOtherService>().To<OtherClass>().InSingletonScope();

但随着同样的错误。

But with same error.

和如何编写只使用一个实例MainClass和IMainService接口绑定？

And how to write binding for using only one instance for MainClass and IMainService interfaces?

感谢您的答案。

推荐答案

由于错误消息说，你之间有循环依赖 MainClass 和 OtherClass 因为你不能没有其他的实例创建一个。理想情况下，你应该调整你的类层次结构删除此要求。

As the error message says, you have a cyclic dependency between MainClass and OtherClass since you can't create one without an instance of the other. Ideally, you should restructure your class hierarchy to remove this requirement.

如果你不能，该解决方案是使用属性注入的类中的一个（或两个） ，如：

If you can't, the solution is to use property injection for one (or both) of the classes, e.g.

public interface IMainService
{
    void DoStuff();
    IOtherService OtherService { set; }
}

public class MainClass
{
    public IOtherService OtherService { get; set; }
    public void DoStuff() { ... }
}

public class OtherService
{
    public OtherService(IMainService main)
    {
        main.OtherService = this;
    }
}

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