Speaking of the above point up 2 I m clearly missing another

Question

Speaking of the above point up 2 I m clearly missing another of the peculiarities of the K N Memory Model Getting the dreaded `Caused by kotlin native concurrent InvalidMutabilityException mutation attempt of frozen kotlin collections HashMap 33944e8` while adding an element to a `MutableSet` However The Set is created while on the main thread The Set is only ever accessed from the main thread I ve asserted these points with checks on `NSThread isMainThread` at every relevant point The top level object under which the Set indirectly resides is marked ` ThreadLocal` which other restriction am I missing Is there a way to determine at what point an object is being frozen

Tijl · Answer

you can call `ensureNeverFrozen` after creating it and then get an exception when something tries to freeze it

darkmoon_uk · Answer

Manna from heaven thanks

darkmoon_uk · Answer

alright so it turns out the freeze was because my Map was being transitively referenced as part of another `object` that wasn t ` ThreadLocal`

darkmoon_uk · Answer

The documentation does I suppose say this is the case

darkmoon_uk · Answer

But I feel like it doesn t make clear enough that any object that is accessible via any part of the object graph beneath a top level `object` will be frozen unless marked ` ThreadLocal` Would it be reasonable for the docs to advise that applying ` ThreadLocal` should be considered a sensible default for newcomers

darkmoon_uk · Answer

or something of that nature

russhwolf · Answer

Agree that docs could be better around all of this but ` ThreadLocal` by default would have it s own set of confusion and drawbacks Anytime you access it from a background thread none of the state you ve set in the main thread will be present but it might not be obvious that something s wrong because nothing will throw

darkmoon_uk · Answer

< russhwolf> Ah I didn t mean to suggest ` ThreadLocal` be an actual language default agree it could cause some serious confusion but rather a suggested way to start for those wanting to avoid the potentially greater complications of object freezing