Question

我有两个类，我想从创建的实例中获取“owner”类的属性，请参阅下面的代码......

class A{      
  String test
  A(){
   //How to get the value of "test" property of the class B from here?
   //
 }
}



class B{

String test

  def doSomething(){
      //I'd like that instance of A get the value of "test" attribute without pass it by param   
      A a = new A() //like this

      A a = new A(test:test) //I don't want to do this


  }

}

Answer 1

试试这个：

def doSomething(){
  A a = new A() 
  a.test
}

Answer 2

没有实例你就无法得到它。 A班不了解B班。您可以使用B作为参数创建构造函数。

class A{
    A(B b){
     println b.test
    }
}

然后你可以在B中使用它：

doSomething(){
  new A(this)
}

Answer 3

不确定这是否是您所追求的，但您可以使用非静态内部类A拥有一种所有权关系。在Groovy中使用与Java相同的工作。

class B {
  class A {
    def knowYourOwner() {
      // access the outer class' property directly via test
      println "My owner says: '$test'"
      // or explicitly via B.this.test (to avoid conflicts with local variables 'test')
      def test = 'another string'
      println "My owner says: '${B.this.test}'"
    }
  }

  String test
  def doSomething() {
    A a = new A()
    a.knowYourOwner()
  }
}

def b = new B(test: 'I am B')
b.doSomething()

Answer 4

您可以将B类的test属性设为静态成员变量

class A { 
  String test

  A() {
    this.test = B.test
  }
}

class B {
  static String test
}

def b = new B(test: "someString")
def a = new A()

println a.test  // outputs : "someString"

如何获得＆＃34;所有者实例＆＃34; Groovy中的类实例？

4 个答案: