I m confuse the use of `SideEffect` I cannot create a case o

Question

I m confuse the use of `SideEffect` I cannot create a case of to differentiate it s use and without it s use as per <https stackoverflow com questions 70720751 whats the different using sideeffect and not using it in jetpackcompose> Can someone enlighten Thank you pray

Big Chungus · Answer

Are you familiar with react hooks

elye · Answer

Sorry I m not familiar with react

elye · Answer

From what I read if the composition is successful then the SideEffect will be triggered I wonder how can I create a case to have a fail composition I just want to experiment in such that the Composable code get called yet the SideEffect is not triggered

FunkyMuse · Answer

Side Effect is triggered every time your mutableStateOf that s wrapped in a remember gets updated

FunkyMuse · Answer

Also whenever your screen gets recomposed config change etc

Big Chungus · Answer

Not entirely true SideEffect gets executed each time its dependencies change If it has no dependencies then it gets executed only when a composable first enters the composition

FunkyMuse · Answer

Side effect runs every time your compose tree is shaken meaning that if you need to update non compose state that s where you d do it

Albert Chang · Answer

You can throw an exception to experiment that

Albert Chang · Answer

< Big Chungus> you are probably talking about `LaunchedEffect` and `DisposableEffect` They are also side effects but the op is asking about `SideEffect` function here

Adam Powell · Answer

there aren t many easily reproducible cases of composition failure that you can create today without leaving the composition in a permanently corrupt and unusable state Those are coming

Adam Powell · Answer

`SideEffect ` schedules the block of code you give it to run when the composition changes are applied It s an output of the composition process but not directly to the composition s tree

Adam Powell · Answer

This scheduling is unconditional There is no snapshot observation happening inside the block you give to SideEffect so if something inside there changes it won t run again without some other reason for the composable function containing the `SideEffect` to recompose

elye · Answer

Thanks < Adam Powell> Thanks for more insight I can understand this ```It s an output of the composition process but not directly to the composition s tree ``` Can you provide an example of how to make this happen ```if something inside there changes``` I m just trying to explore some tangible visible different between the two With and Without SideEffect Block I think if I can find how to trigger that `something` to `change` I can see the different The question is what is that `something` and how to make it `change`

elye · Answer

Identify how I can differentiate them now ``` Composable fun TrySideEffect var timer by remember mutableStateOf 0 Box contentAlignment = Alignment Center Text Time $timer Thread sleep 1000 timer++ ``` and ``` Composable fun TrySideEffect var timer by remember mutableStateOf 0 Box contentAlignment = Alignment Center Text Time $timer SideEffect Thread sleep 1000 timer++ ``` Both will behave differently Don t think it s the best way to explain `SideEffect` but at least that s one way to differentiate with without `SideEffect` Also share my inputs in <https stackoverflow com a 70727052 3286489>

Adam Powell · Answer

`Thread sleep` in composition or in a `SideEffect` is always wrong

Adam Powell · Answer

Both examples of updating a timer here are also wrong for reasons of data flow since they cause composition loops Additionally the first example of changing timer in composition is an example of an out of range write it s invalidating state used by composition after it has already been used

elye · Answer

Agree the first example changing the timer is invalid It is just to demonstrate the use of `SideEffect` The `Thread sleep` is just used to represent busy logic So if one has a busy logic it should never be placed in the composition function at all At most it can be placed in `SideEffect` The above example is not the best way to explain the use of `SideEffect` but it s the simplest way I can think of to differentiate them without adding too many other things that makes understanding it complicated Sorry my brain is limited in digesting concept making the simplest thing possible to help make sense out of things

Adam Powell · Answer

Thread blocking logic shouldn t be placed in a `SideEffect` either It will block the main thread before layout and drawing are permitted to proceed for the current frame

elye · Answer

Good point Hard to think of a simple case that is still clear for the use of SideEffect Any recommendation If we want a simple loop timer would you recommend using `LaunchEffect` or `SideEffect` or some other approach

Adam Powell · Answer

probably a `LaunchedEffect` It s something that happens over time which implies `suspend` and you re describing it as a noun a timer which implies that it has presence in the composition it s not just a change that you apply to some other object

Adam Powell · Answer

The use cases for `SideEffect` are pretty narrow If you re trying to use composition to update some other object that isn t otherwise related to compose in any way but creating a subcomposition with a custom applier would be overkill it comes in handy