groovy - 这个，所有者，Groovy 闭包中的委托(delegate)

Question

这是我的代码:

class SpecialMeanings{
  String prop1 = "prop1"
  def closure = {
    String prop1 = "inner_prop1"  
    println this.class.name //Prints the class name
    println this.prop1
    println owner.prop1
    println delegate.prop1
  }
}

def closure = new SpecialMeanings().closure
closure()

输出是

prop1
prop1
prop1

我希望第一行是 prop1 ，因为它指的是定义闭包的对象。但是，所有者(并且是默认委托(delegate)人)应该引用实际的闭包。所以接下来的两行应该是 inner_prop1。他们为什么不呢？

Answer 1

这就是它的工作原理。 owner的实际引用你要明白和 delegate . :)

class SpecialMeanings{
  String prop1 = "prop1"
  def closure = {
    String prop1 = "inner_prop1"  
    println this.class.name //Prints the class name

    //Refers to SpecialMeanings instance
    println this.prop1 // 1

    // owner indicates Owner of the surrounding closure which is SpecialMeaning
    println owner.prop1 // 2

    // delegate indicates the object on which the closure is invoked 
    // here Delegate of closure is SpecialMeaning
    println delegate.prop1 // 3

    // This is where prop1 from the closure itself in referred
    println prop1 // 4
  }
}

def closure = new SpecialMeanings().closure
closure()

//Example of modifying the delegate to the script itself
prop1 = "PROPERTY FROM SCRIPT"
closure.delegate = this
closure()

脚本的最后 3 行显示了如何更改默认委托(delegate)并将其设置为闭包的示例。上次调用 closure将打印 prop1脚本中的值 PROPERTY FROM SCRIPT在 println # 3