Hi! I got a custom self-made database library (java) which provides a

SqlServer

object for basically everything needed to interact with our database. In Java, we stored that reference in a static variable, as it was accessed and needed in a lot of different places. As there is no "static" in Kotlin, I'm unsure about how do do it properly.

class Database { val sqlServer = SqlServer(...) }

Does not work, as I can't access it from somewhere else

class Database { companion object { val sqlServer = SqlServer(...) } }

Does not work, as I can't pass any configuration

object Database { val sqlServer = SqlServer(...) }

Does not work, no support for constructors or similar

In Java, we do this:

public static void main(String[] args) {
  DbConfig dbCfg = new DbConfig(args);

  Database.init(dbCfg);

  //Database ready to use
  Database.select(...);
}

It would be nice to store the sqlServer object immutable and as a nonnull value. Maybe i'm just dumb rn, it's sort of my first kotlin project. 🙂 Thanks!

moehritz: Where is the

sqlServer

object in your Java code?

@diesieben07

private static SqlServer sqlServer

it is assigned in

public static void init(...)

, and used by the other methods/made public by a getter

Well, apart from the fact that that is terrible OOP design... You need a

var

in Kotlin as well then.

Any suggestions then? It's just impractical not to do it that way, every module of our software accesses this database, and there is always just one

I suggest you take a look at dependency injection. It makes your code a lot more flexible, modular and testable.

I'll take a look, thank you! For now, I settled with initializing it in the main method, storing it there and relying on the fact that Objects are initialized lazily

also you can use

companion object

, see https://kotlinlang.org/docs/reference/object-declarations.html#companion-objects

I would make this an

object Database(val dbCfg: DBConfig) {...}

Constructors are not allowed for objects, so this won't compile @nkiesel

true. So instead a

open class Database(dbConfig: DBConfig) { ... }; object DB : Database(myConfig) { ... }

?