CODEWITHSUNDEEP
kotlin
Fester
Fester

Reputation: 59

Pass variables into parent's constructor in Kotlin

I'm trying to pass through variables from a child class to the parent's constructor.

The parent class' constructor consists of (Context!, String!, SQLiteDatabase.CursorFactory!, Int).

I can easily do 

class TodoListDBHandler(context: Context, databaseName: String, factory: SQLiteDatabase.CursorFactory, databaseVersion: Int): 
    SQLiteOpenHelper(context, databaseName, factory, databaseVersion)

but I would like to specify the database name and version directly inside the class instead of specifying it every time I call the constructor as I might make mistakes.

My current code:

class TodoListDBHandler(context: Context, databaseName: String, factory: SQLiteDatabase.CursorFactory, databaseVersion: Int): 
    SQLiteOpenHelper(context, databaseName, factory, databaseVersion) {

    val databaseFileName = "todoList.db"
    val databaseVersion = 1

    override fun onCreate(db: SQLiteDatabase?) {
        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
    }

    override fun onUpgrade(db: SQLiteDatabase?, oldVersion: Int, newVersion: Int) {
        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
    }
}

As stated above, I would like to be able to pass in the variable I have specified to the parent's constructor.

EDIT: This is the desired code, but in Java

public TodoListDBHandler(Context context, SQLiteDatabase.CursorFactory factory) {
    // databaseFileName and databaseVersion are already specified inside the class
    super(context, databaseFileName, factory, databaseVersion)
}

Upvotes: 2

Views: 2995

Answers (2)

Alexey Romanov
Alexey Romanov

Reputation: 170723

@farhanjk gives a good solution, but you can also put them into the companion object:

class TodoListDBHandler(context: Context, factory: SQLiteDatabase.CursorFactory): 
    SQLiteOpenHelper(context, TodoListDBHandler.databaseName, factory, TodoListDBHandler.databaseVersion) {

    companion object {
        val databaseFileName = "todoList.db"
        val databaseVersion = 1
    }

    ...
}

This can be useful e.g. if there is non-trivial initialization or to create a list just once, etc.

Upvotes: 2

farhanjk
farhanjk

Reputation: 1762

You can pass the constant arguments directly in the super class constructor.

class TodoListDBHandler(context: Context, factory: SQLiteDatabase.CursorFactory)
        : SQLiteOpenHelper(context, "todoList.db", factory, 1) {

        override fun onCreate(db: SQLiteDatabase) {
        }

        override fun onUpgrade(db: SQLiteDatabase, oldVersion: Int, newVersion: Int) {
        }
}

Upvotes: 3

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