How to design a complex class which incude some classes to make expansion easily in future in Kotlin?

Question

I'm a beginner of Kotlin, I use Code A to define a complex class MDetail, and use Code B to create a object aMDetail1, it can work.

But the data construction is too bad to expand, if I include a new data class such as ScreenDef in MDetail just like Code C, all old code have to be rewriten.

Is there a good data construction for a complex class which include some classes ? I hope to the data construction can be expansion easily in future!

Code A

data class BluetoothDef(val Status:Boolean=false)
data class WiFiDef(val Name:String, val Status:Boolean=false)

data class MDetail (
        val _id: Long,
        val bluetooth: BluetoothDef,
        val wiFi:WiFiDef
)

Code B

var mBluetoothDef1= BluetoothDef()
var mWiFiDef1= WiFiHelper(this).getWiFiDefFromSystem()
var aMDetail1= MDetail(7L,mBluetoothDef1,mWiFiDef1)

Code C

data class BluetoothDef(val Status:Boolean=false)
data class WiFiDef(val Name:String, val Status:Boolean=false)
data class ScreenDef(val Name:String, val size:Long)
... 

data class MDetail (
        val _id: Long,
        val bluetooth: BluetoothDef,
        val wiFi:WiFiDef
        val aScreenDef:ScreenDef        
        ...
)

The following code is based what s1m0nw1 said, I think it's easy to extend for future. Thanks!

Is there other more better way?

Version 1 Code

interface DeviceDef

data class BluetoothDef(val Status: Boolean = false) : DeviceDef
data class WiFiDef(val Name: String, val Status: Boolean = false) : DeviceDef
data class ScreenDef(val Name: String, val size: Long) : DeviceDef

class MDetail(val _id: Long, val devices: MutableList<DeviceDef>) {
    inline fun <reified T> getDevice(): T {
        return devices.filterIsInstance(T::class.java).first()
    }
}

class UIMain : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.layout_main)

        val btD = BluetoothDef(true)
        val wfD = WiFiDef("MyWifi")
        val xSc = ScreenDef("MyScreen", 1)
        val m = MDetail(7L, mutableListOf(btD, wfD, xSc))


        handleBluetoothDef(m.getDevice<BluetoothDef>())
        handleWiFiDef(m.getDevice<WiFiDef>())
        handleScreenDef(m.getDevice<ScreenDef>())
    }

    fun handleBluetoothDef(mBluetoothDef:BluetoothDef){ }    
    fun handleWiFiDef(mWiFiDef:WiFiDef){ }    
    fun handleScreenDef(mScreenDef:ScreenDef){ }
}

Version 2 Code (Expansion)

interface DeviceDef

data class BluetoothDef(val Status: Boolean = false) : DeviceDef
data class WiFiDef(val Name: String, val Status: Boolean = false) : DeviceDef
data class ScreenDef(val Name: String, val size: Long) : DeviceDef

data class TimeLine(val Name: String): DeviceDef  //Extend

class MDetail(val _id: Long, val devices: MutableList<DeviceDef>) {
    inline fun <reified T> getDevice(): T {
        return devices.filterIsInstance(T::class.java).first()
    }
}

class UIMain : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.layout_main)

        val btD = BluetoothDef(true)
        val wfD = WiFiDef("MyWifi")
        val xSc = ScreenDef("MyScreen", 1)

        val aTe = TimeLine("MyTimeline")  //Extend

        val m = MDetail(7L, mutableListOf(btD, wfD, xSc,aTe)) //Modified


        handleBluetoothDef(m.getDevice<BluetoothDef>())
        handleWiFiDef(m.getDevice<WiFiDef>())
        handleScreenDef(m.getDevice<ScreenDef>())

        handleTimeLine(m.getDevice<TimeLine>()) //Extend
    }

    fun handleBluetoothDef(mBluetoothDef:BluetoothDef){}    
    fun handleWiFiDef(mWiFiDef:WiFiDef){ }    
    fun handleScreenDef(mScreenDef:ScreenDef){ }           
    fun handleTimeLine(mTimeLine:TimeLine){}  //Extend

Help

I have to replace interface with open class because I can't unserialize MDetail object from json string GSON.

but the fun inline fun <reified T> getDevice(): T{ } can't return correct result, how can I modify? Thanks!

open class DeviceDef

data class BluetoothDef(val status:Boolean=false):  DeviceDef()
data class WiFiDef(val name:String, val status:Boolean=false) : DeviceDef()

data class MDetail(val _id: Long, val deviceList: MutableList<DeviceDef>)
{
    inline fun <reified T> getDevice(): T {        
        return deviceList.filterIsInstance(T::class.java).first()
    }
}

Answer 1

I suggest to do the following: Your units (Wifi, Bluetooth etc.) should be abstracted by an interface (at least as a marker), which could be named DeviceDef.

interface DeviceDef
data class BluetoothDef(val Status: Boolean = false) : DeviceDef
data class WiFiDef(val Name: String, val Status: Boolean = false) : DeviceDef
data class ScreenDef(val Name: String, val size: Long) : DeviceDef 

The MDetail class can be instantiated with a variable list of these devices, so that no modifications are needed when new devices, such as ScreenDef, are added:

class MDetail(val _id: Long, val devices: List<DeviceDef>)

Inside MDetail, you can provide a method for filtering these devices:

class MDetail(val _id: Long, val devices: List<DeviceDef>) {

    inline fun <reified T> getDevice(): T {
        return devices.filterIsInstance(T::class.java).first()
    }
}

Now, it's pretty simple to work with the WifiDef for example:

fun main(args: Array<String>) {
    val btD = BluetoothDef()
    val wfD = WiFiDef("")
    val m = MDetail(7L, listOf(btD, wfD, ScreenDef("", 1)))
    println(m.getDevice<WiFiDef>())
}

I hope this helps. If not, it might be necessary that you provide more details on how MDetail is supposed to work.