How do I get the class (scope) from which a closure is called in Groovy? -

class box {     closure click      box () {         click = {}     }      void onclick() {         click()     } }  class textbox extends box {     list<string> content      textbox (string[] a) {         super()         content =     } }  class main {     public static void main(string[] args) {         main m = new main()     }      main() {         string[] = ["hello world!"]         box b = new textbox(a)         b.click = {content.add("you clicked box!")}         b.onclick()  //throws exception     } } 

(the above is, obviously, simplification; in reality, classes bit more involved, , calling of onclick() due click on jframe)

now, when try run (i.e. run main.main()), exception: exception in thread "awt-eventqueue-0" groovy.lang.missingpropertyexception: no such property: content class: main

clearly, is, reason, searching list in main, not in textbox or box, called. tried using this, owner , delegate, point main well. managed have work giving argument:

... void onclick() {     click(this) } ... b.click = {it.content.add("you clicked box!")} 

it seems, however, weird need pass "this" closure able know called from. isn't there more elegant solution? also, if indeed impossible textbox-scope, somehow possible box-scope?

main() {     string[] = ["hello world!"]     box b = new textbox(a)     println "1:- $b.click.delegate" //will print textbox     b.click = {         println "2:- $b.click.delegate" //will print main          //since closure defined inside main(),          //main becomes delegate. reset delegate textbox.         b.click.delegate = b          println "3:- $b.click.delegate" //will print textbox         content.add("you clicked box!")     }     println "4:- $b.click.delegate" //will print main     b.onclick()      println b.content //will print [hello world!, clicked box!] }  //output: 1:- textbox@c166770 4:- main@6dbdc863 2:- main@6dbdc863 3:- textbox@c166770 [hello world!, clicked box!] 

points note:

• sequence 4 present before 2 , 3 since closure not called/invoked @ point of time.
• sequence 1 prints textbox sequence 4 prints main. note delegate has changed (after defining closure b.click) textbox main now.

to make things easier, instead of changing things in main, can modify onclick() as

void onclick() {     click.delegate =     click() } 

refer this script details.