how to auto fill combobox in tornadofx

AutoFill.kt

package com.example.demo.view
import org.junit.Assert
import org.junit.Test
import org.testfx.api.FxToolkit
import org.junit.Assert.*
import javafx.beans.property.SimpleStringProperty
import javafx.scene.Node
import javafx.scene.control.*
import javafx.scene.layout.Background
import javafx.scene.layout.BackgroundFill
import javafx.scene.layout.BackgroundSize
import javafx.scene.paint.Color
import javafx.scene.text.Font
import tornadofx.*
import tornadofx.controlsfx.statusbar
import java.io.FileInputStream
import javax.json.JsonObject
import org.junit.Assert.*

class testAuto : View("My View",Button("op")) {

    var js="""
        [
        {"name":"abdo"
        "password":"796990"



        ]
    """.trimIndent()
private var nmtxt: TextField by singleAssign()
    var pstxt:PasswordField by singleAssign()
var model =personModel()
    override val root = form {


        fieldset {
            this.style{
                backgroundColor+=Color.CADETBLUE
                font= Font.loadFont(FileInputStream("F:\\Fonts\\LHANDW.TTF"),20.0)

            }
            field("username") {
          textfield(model.name) {
              nmtxt=this
          }.required()
            }
            field("password") {
              passwordfield(model.password) {
pstxt=this
                }.required()
            }
            button("Log in")
            {
                useMaxSize = true
                style {
                    backgroundColor += Color.GREEN

                }
                action{
                    model.commit()

                }
            }
        }
    }
    private var context=ValidationContext()


    var nmval=context.addValidator(nmtxt,nmtxt.textProperty()){
        if(it!!.length<5) error("short name , please check name") else null
    }
var psval=context.addValidator(pstxt,pstxt.textProperty()){
    if(it!!.contains("2012")  ) null else {error("invalid password ,plz check password")}
if (it!!.contains("2012")) success("great") else warning("oops")

}







}

class person{
    var name=SimpleStringProperty()
    var nmProperty by name
    var password =SimpleStringProperty()
    var pass by password
}

class personModel:  ItemViewModel<person>(){

    var name=bind(person::nmProperty)
    var password=bind(person::pass)
}

Ooops!

this is a code

package com.example.demo.view

import javafx.beans.property.SimpleStringProperty
import javafx.collections.ObservableList
import javafx.scene.control.ComboBox
import javafx.scene.control.SelectionMode
import javafx.scene.control.SelectionModel
import tornadofx.*
import java.io.FileInputStream

class testcss : View("test css") {
var ic=icons()
init {

    icon=ic.googleIcon
}
var comb1:ComboBox<String> by singleAssign()
var loc2 = listOf(stat("khartoum", listOf("umbada", "bahri", "jabel awliaa")), stat("nahr al-neel", listOf("atbara"))).observable()
var ct = loc2.map { it.name.trim() }
var xc: ObservableList<String>? = listOf("choose city").observable()
var str:String?="khartoum"
var l = SimpleStringProperty()
var s = SimpleStringProperty(ct.first())
override val root = vbox {
   comb1= combobox(s, ct) {
        makeAutocompletable()

selectionModel.selectedItemProperty().onChange {
str = selectionModel.selectedItem!!.toString()
}
print(locss(str!!))
println(str)

    }





    combobox(values = xc) {

        makeAutocompletable()

comb1.selectionModel.selectedItemProperty().onChange {
items=locss(str!!)
}

    }

}

fun locss(s: String):ObservableList<String>? {
    xc = when (s) {
        "khartoum"-> listOf("bahri", "kassala", "umbad").observable()
        "nahr al-neel"-> listOf("fifi", "hyigoi", "gggooiho").observable()
        else -> listOf("konakre","melborne").observable()
    }

return xc?.observable()
}
}
package com.example.demo.view

import javafx.beans.property.SimpleStringProperty
import javafx.collections.ObservableList
import javafx.scene.control.ComboBox
import javafx.scene.control.SelectionMode
import javafx.scene.control.SelectionModel
import tornadofx.*
import java.io.FileInputStream

class testcss : View("test css") {
var ic=icons()
init {

    icon=ic.googleIcon
}
var comb1:ComboBox<String> by singleAssign()
var loc2 = listOf(stat("khartoum", listOf("umbada", "bahri", "jabel awliaa")), stat("nahr al-neel", listOf("atbara"))).observable()
var ct = loc2.map { it.name.trim() }
var xc: ObservableList<String>? = listOf("choose city").observable()
var str:String?="khartoum"
var l = SimpleStringProperty()
var s = SimpleStringProperty(ct.first())
override val root = vbox {
   comb1= combobox(s, ct) {
        makeAutocompletable()

selectionModel.selectedItemProperty().onChange {
str = selectionModel.selectedItem!!.toString()
}
print(locss(str!!))
println(str)

    }





    combobox(values = xc) {

        makeAutocompletable()

comb1.selectionModel.selectedItemProperty().onChange {
items=locss(str!!)
}

    }

}

fun locss(s: String):ObservableList<String>? {
    xc = when (s) {
        "khartoum"-> listOf("bahri", "kassala", "umbad").observable()
        "nahr al-neel"-> listOf("fifi", "hyigoi", "gggooiho").observable()
        else -> listOf("konakre","melborne").observable()
    }

return xc?.observable()
}
}
data class stat(var name:String, var local:List)