Creating a mutable variable in a singleton results...

# kotlin-native

[Animesh Sahu]

Creating a mutable variable in a singleton results in the following warning:

object MySingleton {
    private var testingVar = false
}

Variable in singleton without @ThreadLocal can't be changed after initialization.

On annotating with @ThreadLocal results in error: @ThreadLocal is applicable only to top level declarations

[Animesh Sahu]

Is this intended or a bit misleading?

[Tijl]

annotate your entire object, not the field

[Animesh Sahu]

@Tijl Hey, Thanks! If I annotate the whole object, then what about the immutable val fields, would they be different from different threads?

[Tijl]

yes

[Animesh Sahu]

So, putting them on top level will be better? I mean I don't want my immutable variables to hold different references local to the thread.

[Tijl]

You’re trying to make a global variable, which is usually not a good idea so I’d encourage you to think about your design.

However, you can check out AtomicBoolean from Kotlin native (use expect/actual to access it, or the stately library)

[Animesh Sahu]

Ohh thanks, atomic types seems to be perfect here, though there's no AtomicBoolean I'd probably use AtomicInt 🙂

[Tijl]

Ah yes it’s a util class in Stately

[Tijl]

keep in mind that on the JVM cross thread access is not atomic by default either, you need at least @Volatile