Hi all I am having trouble with an object getting ...

# multiplatform

[william]

Hi all I am having trouble with an object getting frozen in its init block and then top level value assignments causing an exception. heres a min example:

class Foo(bar: Bar) {
    init {
        CoroutineScope(Dispatchers.Default).launch { 
            bar.buzz()
        }
    }
    
    val a = 3
}

in the init block since bar is accessed, it seems like that is causing the entire foo object to also get frozen

then when it gets to val a = 3 during runtime - it complains about foo instance already being frozen. how can i go about fixing this?

[mbonnin]

Maybe try initiliazing a before launching the coroutine ?

[russhwolf]

If bar is just a constructor parameter and not a property of Foo (eg val bar: Bar) then I wouldn’t expect the whole Foo to get frozen by that init block.

[russhwolf]

but yeah try initializing a first

[mbonnin]

Yep, agreed that I wouldn't expect the whole Foo to be frozen there.

[mbonnin]

You can also use ensureNeverFrozen , sometimes that helps debugging where something becomes frozen

[william]

just checked my actual code, looks like i reference a constructor parameter, as well as a constructor property (didn't show that in my simplified code), so I'm guessing thats why it is frozen

[william]

so it sounds like i can't start up that coroutine in the init block like i am now hmm. maybe i'll need to add a start function on my class or similar

[russhwolf]

If you started from something like this

class Foo(val bar: Bar) {
    init {
        CoroutineScope(Dispatchers.Default).launch { 
            bar.buzz()
        }
    }
}

then you can refactor like this to avoid freezing Foo

class Foo(bar: Bar) {
    val bar = bar // need to suppress a warning here
    init {
        CoroutineScope(Dispatchers.Default).launch { 
            bar.buzz()
        }
    }
}

[russhwolf]

bar will still be frozen but there won’t be a this reference inside the coroutine stuff to freeze the whole Foo

[william]

thanks guys for the help! i was able to change the constructor property to just a parameter and that fixed this one. Russell thats a neat trick - i'm hoping i wont need to use that but good to know

[william]

looking forward to this new memory model that they have talked about at times