Hey, is there some way to check if a lazy variable is initialized without using reflections?

# getting-started

[Anthony Flores]

Hey, is there some way to check if a lazy variable is initialized without using reflections?

[Sam]

You mean like this?

val lazy: Lazy<String> = lazy { "foo" }
val isInitialized = lazy.isInitialized()

[Anthony Flores]

Yes

[Sam]

The above will work fine but obviously doesn't work with property delegation

[Sam]

So what you can't do is

val lazy: String by lazy { "foo" }
val isInitialized = lazy.isInitialized() // doesn't work

[Anthony Flores]

Alright I will try it, thanks.

[Sam]

A compromise would be something like

val lazyFoo: Lazy<String> = lazy { "foo" }
val foo by lazyFoo
val fooIsInitialized = lazyFoo.isInitialized()

[Joffrey]

Also whatever you do with this information will suffer from the same concurrency issues that lazy is saving you from

[Sam]

I suppose technically you could write

val foo: String by lazy { "foo" }
val isInitalized = (::foo.getDelegate() as Lazy<*>).isInitialized()

but I wouldn't recommend it (and it doesn't help with the concurrency issue)

[Anthony Flores]

The code isn't going to be multithreaded so I doubt it's a big deal

[Joffrey]

Could you please share your use case for needing this in the first place?

[Anthony Flores]

I'm not super sure if I even need this in the first case, but it's for a UI Component system. The superclass has 5 separate ArrayLists per component for each and every "listener" (e.g. MousePressed, MouseEntered etc...) but I might not use all of the listeners for each component, and since some screens might be initializing 100+ components, it might create a frame drop when opening the screen.

[Anthony Flores]

Of course, this could just be an oversight on my behalf, and I'm overcomplicating this, and it is unnecessary.

[Youssef Shoaib [MOD]]

maybe it would be a good idea to use a lateinit var instead? because with that you may do object::propertyName.isInitialized and under the hood it doesn't actually use reflection

[Joffrey]

5 separate ArrayLists per component for each and every "listener"

Not sure I understand the cardinality here. Is that:

• 5 arraylists per component per listener? In that case what is the 5 here?
• 1 arraylist per component per listener, and there are 5 listeners per component?
In any case, what are the elements of those lists? And are those lists lazy properties themselves or are the lists regular properties but containing lazy items?

[Joffrey]

Also, you have somewhat described your need for lazy, but not the need for knowing that the lazy is initialized. This is mostly what I'm interested in (in case it's an XY problem)

[Anthony Flores]

An array would be like val mousePressedListener = ArrayList<UIComponent.() - Unit>()

[Anthony Flores]

And, yeah I should have presented my problem, and then what my attempted solution was instead of what I did.