groovy(5)闭包委托策略

package variable

/*

• 闭包的三个重要变量:this,owner,delegate

• 区别在于:this代表闭包定义处最近的对象(不包含闭包),owner代表闭包定义出最近的对象可以是闭包.delegate默认与owner一致.

• delegate可以修改

• */

1. scriptClouser={

   println("scriptClouser this::"+this)
   println("scriptClouser owner:::"+owner)
   println("scriptClouser delegate::::"+delegate)//所以大部分情况下 ,this,owner,delegate 是一样//以上三个输出的结果是一样的/*scriptClouser this::variable.Clousershujujiegou@17046283
   scriptClouser owner:::variable.Clousershujujiegou@17046283
   scriptClouser delegate::::variable.Clousershujujiegou@17046283*/

}
scriptClouser.call()
//文件中定义一个内部类
class Preson{

//类中的闭包

def static classClouse={

   println("bscriptClouser this::"+this)//bscriptClouser this::class variable.Preson
   println("bscriptClouser owner:::"+owner)//bscriptClouser owner:::class variable.Preson
   println("bscriptClouser delegate::::"+delegate)//bscriptClouser delegate::::class variable.Preson

}

//类中的方法的闭包def static fun(){
    def  classClouse={
        println("funscriptClouser this::"+this)//funscriptClouser this::class variable.Preson
        println("funscriptClouser owner:::"+owner)//funscriptClouser owner:::class variable.Preson
        println("funscriptClouser delegate::::"+delegate)//funscriptClouser delegate::::class variable.Preson
    }
    classClouse.call()
}

}
Preson.classClouse.call()
Preson.fun()
//输出的都是 类的 字节码文件对象.class variable.Preson.因为是静态的方法

class Preson2{

//类中的闭包def  classClouse={
    println("p2bscriptClouser this::"+this)//p2bscriptClouser this::variable.Preson2@1dde4cb2
    println("p2bscriptClouser owner:::"+owner)//p2bscriptClouser owner:::variable.Preson2@1dde4cb2
    println("p2bscriptClouser delegate::::"+delegate)//p2bscriptClouser delegate::::variable.Preson2@1dde4cb2}//类中的方法的闭包def  fun(){
    def  classClouse={
        println("p2funscriptClouser this::"+this)//p2funscriptClouser this::variable.Preson2@1dde4cb2
        println("p2funscriptClouser owner:::"+owner)//p2funscriptClouser owner:::variable.Preson2@1dde4cb2
        println("p2funscriptClouser delegate::::"+delegate)//p2funscriptClouser delegate::::variable.Preson2@1dde4cb2
    }
    classClouse.call()
}

}
Preson2 p2=new Preson2();
p2.classClouse.call()
p2.fun()

//总结1:对象中包含闭包:this,owner,delegate指向的都是离他最近的一个类或对象
//scriptClouser中的this,owner,delegate ,输出结果是variable.Clousershujujiegou@17046283(即文件对应的对象)
//对应的静态方法中Person中输出的是class variable.Preson ,Person2中输出的是variable.Preson2@1dde4cb2(即文件中包含闭包的类对应的对象)

//闭包中定义一个闭包
def nestClouser={

def innerClouser={
    println("innerfunscriptClouser this::"+this)//innerfunscriptClouser this::variable.Clousershujujiegou@9225652
    println("innerfunscriptClouser owner:::"+owner)//innerfunscriptClouser owner:::variable.Clousershujujiegou$_run_closure2@72057ecf
    println("innerfunscriptClouser delegate::::"+delegate)//innerfunscriptClouser delegate::::variable.Clousershujujiegou$_run_closure2@72057ecf}
innerClouser.delegate=p2//delegate修改后:innerfunscriptClouser delegate::::variable.Preson2@6eda5c9innerClouser.call()

}
nestClouser.call()
//总结2:闭包中包含闭包:this指向他所定义处的文件对象,owner指向离他最近的闭包nestCloust的一个对象,二delegate默认和owner一致.

/*

闭包的委托策略
Closure.OWNER_FIRST
Closure.OWNER_ONLY
Closure.DELEGATE_FIRST
Closure.DELEGATE_ONLY

*/
class Student{

String name
def pretty={"my name is ${name}"}String toString(){
    pretty.call()
}

}
class Teacher{

String name

}
def stu=new Student(name:'lich')
def teacher=new Teacher(name:'lilei')
println(stu.toString())//my name is lich.
//stu的name是通过构造方法传递的,我们通过更改其委托,让他指向teacher对象的name
stu.pretty.delegate=teacher
//将stu中的pretty闭包的delegate指向为teacher对象,但是因为其默认的委托策略还是Closure.OWNER_FIRST(优先从owner中找),所以要设置为Closure.DELEGATE_FIRST(让他优先从delegate中找)
stu.pretty.resolveStrategy=Closure.DELEGATE_FIRST
println(stu.toString())//my name is lilei
//当我们把Teacher中name去掉后,delegate中找不到时,他又会从owner中去找,所以讲teacher中的name去掉后,结果是:my name is lich.当把stu的委托策略改成Closure.DELEGATE_ONLY时,会报错,因为此时找不到name

原文链接：http://www.apkbus.com/blog-953329-77634.html