unity 解决循环依赖 [英] Unity resolving cyclic dependency

问题描述

在学习 Unity(C# 中的 DI 框架)时，我遇到了一种情况，其中一个类具有 ClassB

While learning Unity (DI framework in C#) I came across a situation where one class has a setter injection of ClassB

class ClassA : IClassA
{
    [Dependency]
    public IClassB ClassB
    {
        get { return _classB; }
        set
        {
            if (value == null) throw new ArgumentNullException("value");
            _classB = value;
        }
    }

另一个有ClassA

class ClassB : IClassB
{
    [InjectionConstructor]
    public ClassB(IClassA classA)
    {
        _classA = classA;
    }
}

我无法在容器内正确解析这两个类.

I am not able to resolve both the classes correctly within the container.

var container = new UnityContainer();
container.RegisterType<IClassB, ClassB>();
container.RegisterType<IClassA, ClassA>();
IClassA classA = new ClassA();
var instance = container.Resolve<ClassA>();
instance.DoSomethingFromClassB();

log.Info("Constructor Injection");
var instanceB = container.Resolve<ClassB>();
instanceB.DoSomethingFromClassA();

这给了我一个堆栈溢出异常

This gives me a stack overflow exception

我尝试了不同的解决顺序，但似乎不起作用.

I tried different ordering of resolving this but it doesn't seem to work.

我这是可行的，还是我只是在浪费时间.

I this doable or am I just wasting my time.

这里到底发生了什么?

推荐答案

我同意@Haney 的观点，这是一种代码异味，但在技术上是可行的...

I agree with @Haney that this is a code smell, but it is technically possible...

只需更改要通过 Lazy 解析的引用类型之一.然后它不会真正解析那个类型，直到它被使用，这将打破无限递归循环.

Just change one of the referenced types to be resolved via Lazy<T>. Then it does not actually resolve that type until it is used which will break out of the infinite recursion loop.

即

class ClassB : IClassB
{
...
    [InjectionConstructor]
    public ClassB(Lazy<IClassA> classA)
    {
        _classA = classA;
    }
}

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