如何初始化循环依赖（最终的字段引用对方）？ [英] How to initialize a circular dependency (final fields referencing each other)?

问题描述

如何初始化这个：

  class A {
 final B b; 
 
 A（B b）{
 this.b = b; 
} 
} 
 
 class B {
 final A a; 
 
 B（A a）{
 this.a = a; 
} 
} 
  

DI框架，反思，更好的设计？ >

动机和用例（添加）：

我的具体用例是简化字段访问 A 和 B 的子类。所以我注意到他们很快地引用了派生类中的字段，而不需要在每个子类中明确声明。

还有一个关于DI的建议，对象应该是不可改变的： Guice最佳做法和反模式。

解决方案

您可以使用工厂方法

  class A {
 final B b; 
 
 A（B b）{
 this.b = b; 
} 
} 
 
抽象类B {
 final A a; 
 
 B（）{
 this.a = constructA（）; 
} 
 
 protected abstract A constructA（）; 
} 
 
 public class C {
 public static void main（String [] args）{
 new B（）{
 protected A constructA（） {
 return new A（this）; 
} 
}; 
} 
} 
  

How do you initialize this:

class A {
    final B b;

    A(B b) {
        this.b = b;
    }
}

class B {
    final A a;

    B(A a) {
        this.a = a;
    }
}

DI framework, reflection, better design?

Motivation and a use case (added):

My particular use case is simplifying field access in A's and B's sub-classes. So I'm injecting them to shortly reference them by fields in the derived classes without a need to declare explicitly in each sub-class.

There is also a recommendation on DI that objects should better be immutable: Guice best practices and anti-patterns.

解决方案

You could use a factory method

class A {
    final B b;

    A(B b) {
        this.b = b;
    }
}

abstract class B {
    final A a;

    B() {
        this.a = constructA();
    }

    protected abstract A constructA();
}

public class C {
    public static void main(String []args){
        new B(){
            protected A constructA(){
                return new A(this);
            }
        };
    }
}

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