Inner data classes

Issue

Could someone give me a little pointer on data classes. I'm finding a very steep learning curve with Kotlin, but I'm getting there slowly.

I have a data class of:

data class newGame(
    val gamename: String,
    val gamedate: String,
    val players: List<Player>
) {
    data class Player(
        val player: String,
        val player_id: Int,
        val score: Int,
        val points: Int
    )
}

I can create an instance of the outer (newGame) class, but I'm struggling to get to grips with how I add Players. I thought I could do something like:

var gm: newGame

gm.gamename = GamesList.text.toString()

val p = newGame.Player
p.player = Player1.text.toString()

gm.players.add p

But Android Studio says I need a companion object and I'm not sure how that needs to look

The interface looks like:

interface CreateGame {
    @POST("new")

    fun addNewGame(
        @Query("operation") operation: String,
        @Body() newGame: newGame
    ): Call<gameEvent>

companion object {

    fun create(): CreateGame {

        val retrofit = Retrofit.Builder()
            .addConverterFactory(GsonConverterFactory.create())
            .baseUrl(BaseURL)
            .build()
        return retrofit.create(CreateGame::class.java)
    }
}

I get how the companion object create() creates the instance of the game, but I can't figure out what I need to write so that I can add players to the inner class.

Could someone give me a pointer please?

Solution

I can create an instance of the outer (newGame) class, but I'm struggling to get to grips with how I add Players. I thought I could do something like:

Well, first understood the terms val and var. The property gamename is val which means its read-only, to write it you have to make it as var, same goes to all other properties. and players should be mutableListOf or ArrayList<> type so you can modify it later. List is immutable, which means you can't add after initialization.

data class newGame(
    var gamename: String,
    var gamedate: String,
    var players: ArrayList<Player>
)
data class Player(
    var player: String,
    var player_id: Int,
    var score: Int,
    var points: Int
)

Now In your case, you need to add a secondary constructor OR initialize all properties while declaring as below

data class newGame(
    var gamename: String? = null,
    var gamedate: String? = null,
    var players: ArrayList<Player> = ArrayList()
)
data class Player(
    var player: String?=null,
    var player_id: Int?=null,
    var score: Int?=null,
    var points: Int?=0
)

In main class

    var gm: newGame = newGame()

    gm.gamename = "GamesList.text.toString()"

    val p = Player()
    p.player = "Player1.text.toString()"

    gm.players.add(p)

Answered By - Shoaib Khalid