I've seen people doing: ``` private val _foo by la...

# android

[ghedeon]

I've seen people doing:

private val _foo by lazy { MutableLiveData()}

val foo: LiveData by lazy { _foo } // why second lazy?

Does this second lazy really make sense? Seems like val foo: LiveData = _foo val foo: LiveData get() = _foo should be enough.

[marstran]

I think val foo: LiveData = _foo would initialize _foo immediately. To keep it all lazy, foo must be lazy as well.

[ghedeon]

val foo: LiveData get() = _foo?

[marstran]

That should work I think. Try it to see what happens.

[ghedeon]

yep, the lazy is redundant: https://pl.kotl.in/rko7o8XfN

[ghedeon]

another question is tho, if you have transformations:

val foo: LiveData get() = _foo.map{}...

vs

val foo: LiveData by lazy { _foo.map{}... }

I suppose in this case lazy will cache the map lambda?

[Allan Wang]

Correct. You can look at the source and see that lazy will only execute the block if the stored value is UNINITIALIZED

[radityagumay]

No need for 2nd lazy

[Hadi Tok]

I couldn’t understand why lazy is used to init LiveData. I know what it does but why?

[ghedeon]

You won't gain much if it's a livedata that is being observed all the time the view is alive. But you can have some livedatas that you subscribe to under a certain condition, so if condition is false — you don't create it for nothing.

[Allan Wang]

I haven't really used it (I've been trying Channels instead), but given livedata is the observable, aren't you going to inevitably send data to it?

[ghedeon]

not, unless you observe it. It's pretty much a very primitive version of Rx stream (BehaviorSubject).

[Allan Wang]

How are you going to post events without initializing the livedata? Whether or not you use the events is a different story. Similarly with publish/behavior subject and channels; wasn't the point that the observable did not have to be aware of the observers when sending content?

[Hadi Tok]

Thanks for explaining.