how do I build a tree hierarchy from a list in groovy using recursive closure?

closures, grails, groovy

Solution

like this...?

def root = new Work(code:'*', title:'ROOT')

def build 

build = { p, list ->
  list.groupBy{it.code.split('\\.').first()}.each{ el, sublist ->
    el = sublist[0]        
    el.parentWork = p
    if(sublist.size()>1){
        build(el, sublist[1..-1] )
    }
  }

}
build(root, works.sort{it.code.length()})

if I'm not in error even in this anonim form may work

def root = new Work(code:'*', title:'ROOT')

{ p, list ->
  list.groupBy{it.code.split('\\.').first()}.each{ el, sublist ->
    el = sublist[0]        
    el.parentWork = p
    if(sublist.size()>1){
      call(el, sublist[1..-1] )
    }
  }

}(root, works.sort{it.code.length()})

Problem

I defined the recursive domain class in grails: ``` class Work { String code String title String description static hasMany = [subWorks:Work] static mappedBy = [subWorks: 'parentWork'] Work getRootWork(){ if(parentWork) return parentWork.getRootWork() else return this } boolean isLeafWork(){ return subWorks.isEmpty() } boolean isRootWork(){ return !parentWork } ``` I have a list of Works, but the hierarchy structure is not built yet. The structure looks like: ``` def works = [new Work(code:'A', title:'TitleA'), new Work(code:'B', title:'TitleB'), new Work(code:'A.1', title:'Titile A.1'), new Work(code:'B.1', title:'Title B.1'), new Work(code:'B.2', title:'Title B.2'), new Work(code:'B.3', title:'Title B.3'), new Work(code:'B.2.2', title:'Title B.2.2'), new Work(code:'B.2.3', title:'Title B.2.3'), new Work(code:'A.1.1', title:'Title A.1.1'), new Work(code:'A.1.2', title:'Title A.1.2'),] ``` What I need is to build the hierarchical relationship among these works, based on the code hinted. e.g. A.1 is the first child work of A; B.1.1 is the first child of B.1 work, whose parent is B work. I know that Groovy supports recursive closures to build this kind of hierarchical structure. How do I achieve my goal using Groovy recursive closure, such as the JN2515 Fibonacci number example, in Groovy official documentation? Many thanks!

Original source