Setters don't modify two-dimensional array - kotlin

Question

Kotlin. I want a button to display values from a two-dimensional ArrayList, and a second button to modify one of them. But the setters don't modify the two-dimensional ArrayList. We can see the values with the first button, and after modifying the values at index 2 (third) with the second button, the values don't change:
model.get(2).setDateStrs("03/03/20")
model.get(2).setHourStrs("10:27")
What's wrong?
ReModel.kt file:
package com.example.updatearraylist
class ReModel {
var dateStr:String = "12/31/2029"
var hourStr: String = "00:00"
fun getDateStrs(): String {
return dateStr
}
fun setDateStrs(dateStr: String) {
this.dateStr = dateStr
}
fun getHourStrs(): String {
return hourStr
}
fun setHourStrs(hourStr: String) {
this.hourStr = hourStr
}
}
MainActivity.kt file:
package com.example.updatearraylist
import android.R.attr
import android.app.Activity
import android.content.Intent
import android.os.Bundle
import android.widget.Button
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*
import java.lang.reflect.Array.get
import java.util.*
import kotlin.collections.ArrayList
class MainActivity : AppCompatActivity() {
private var displayValueBtn: Button? = null
private var changeValueBtn: Button? = null
val model: ArrayList<ReModel>
get() {
val list = ArrayList<ReModel>()
for (i in 0..7) {
val model = ReModel()
model.setDateStrs("01/16/2020")
model.setHourStrs("01:08")
list.add(model)
}
return list
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
displayValueBtn =findViewById<Button>(R.id.displayValueBtn)
changeValueBtn=findViewById<Button>(R.id.changeValueBtn)
displayValueBtn!!.setOnClickListener {
for(i in 0..7){
Toast.makeText(this, "Value position "+i+" "+model.get(i).getDateStrs()+" "+
model.get(i).getHourStrs()
,Toast.LENGTH_SHORT).show()
}
}
changeValueBtn!!.setOnClickListener {
model.get(2).setDateStrs("03/03/20")
model.get(2).setHourStrs("10:27")
Toast.makeText(this,"List Modified",Toast.LENGTH_LONG).show()
}
}
}

Answer 1

The custom getter on model will be executed each time model is accessed so any changes to the array are overwritten. If you want to verify that use a single println in the custom getter and whatever you print will display multiple times.
By "custom getter" I mean the get() on model and the associated block of code.
One solution is to use lazy initialization instead of a custom getter so that model is initialized only once. Here's how that would look:
val model: ArrayList<ReModel> by lazy {
val list = ArrayList<ReModel>()
for (i in 0..7) {
val model = ReModel()
model.setDateStrs("01/16/2020")
model.setHourStrs("01:08")
list.add(model)
}
list
}
Note that the last line with just list on it returns the value of list. return is not allowed there.