Groovy闭包委托定义参数？

Question

I'm learning groovy delegate

class GroovyGreeter {
    String greeting = "Default greeting"
    def printGreeting(){println "Greeting: $greeting"}
}
def myGroovyGreeter = new GroovyGreeter()
myGroovyGreeter.printGreeting() // default 
myGroovyGreeter.greeting = "My custom outer greeting"
myGroovyGreeter.printGreeting()
def greetingClosure = {
    println greeting  //equal to delegate.greeting
    println this.class
    println owner.class
    println delegate.class
    greeting = "Setting the greeting from a closure" // this is ??????
    printGreeting()
    delegate.greeting = "setting the greeting from delegate.greeting..."
    printGreeting()
}
greetingClosure.delegate = myGroovyGreeter
greetingClosure() // This works as `greeting` is a property of the delegate

os: windows10 terminal:cywin groovy:2.4.10 jvm 1.8

Greeting: Default greeting
Greeting: My custom outer greeting
My custom outer greeting
class closureuda
class closureuda
class GroovyGreeter
Greeting: My custom outer greeting
Greeting: setting the greeting from delegate.greeting...

I'm confused about why the variable of greeting in the closure is not equeal to the delegate.greeting

When i decopile the code and found that —— the greeting is define as a local variable:

private static /* synthetic */ CallSiteArray $createCallSiteArray() {
    String[] strArr = new String[1]; // this  is greeting definition
    strArr[0] = "printGreeting";
    return new CallSiteArray(closureuda$_run_closure1.class, strArr);
}

Answer 1

Groovy by default will look at the closure's scope before going to the delegate, so for setting things that you want in the delegate, this is probably not what you want... Luckily, you can change the resolve strategy with:

greetingClosure.resolveStrategy = Closure.DELEGATE_FIRST

Put this immediately after the line

greetingClosure.delegate = myGroovyGreeter

and you should get the output you were expecting