Hi! I got a custom self-made database library (ja...

# getting-started

[moehritz]

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!

[diesieben07]

moehritz: Where is the sqlServer object in your Java code?

[moehritz]

@diesieben07 private static SqlServer sqlServer
it is assigned in public static void init(...), and used by the other methods/made public by a getter

[diesieben07]

Well, apart from the fact that that is terrible OOP design... You need a var in Kotlin as well then.

[moehritz]

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

[diesieben07]

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

[moehritz]

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

[tapchicoma]

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

[tapchicoma]

though better to use dependency injection

[nkiesel]

I would make this an object Database(val dbCfg: DBConfig) {...}

[moehritz]

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

[nkiesel]

true. So instead a open class Database(dbConfig: DBConfig) { ... }; object DB : Database(myConfig) { ... } ?