Hallo. Curious about how many people use any form ...

# android

[stantronic]

Hallo. Curious about how many people use any form of kotlin reflection in Android apps? Cant find any resources on how much this is encouraged / discouraged.

[wasyl]

Do you have any specific use case in mind? I don’t think I use any reflection at this time, but e.g. Retrofit does use Java reflection to create an implementation of the API interface (https://github.com/square/retrofit/blob/master/retrofit/src/main/java/retrofit2/HttpServiceMethod.java) but it also caches some stuff (https://github.com/square/retrofit/blob/master/retrofit/src/main/java/retrofit2/Retrofit.java#L192-L193) so that it doesn’t use Reflection often.

[wasyl]

I think the overall sentiment is that reflection is slow and shouldn’t be used often, but also not slow enough not to be used ever 😉
*I don’t have sources for that statement though

[Adam Powell]

Avoid it. The kotlin-reflect library is large in terms of apk size and reflection is indeed slow. This is compounded on Android since the system expects to be able to kill -9 your app at any time and restart it any time it's needed, so one-time reflection that is cached still hurts your ability to become interactive quickly or launch work in the background like handling broadcasts or jobs.

[Adam Powell]

If you can do it statically, it's generally worth that approach instead, even if that means code generation

[Alowaniak]

Reflection can also break easier IMO
I guess ideally tests would catch that for you, but that's not always airtight in my experience

[stantronic]

Thanks guys. Current use case is diffing various data classes against each other to see which fields are different - idea is to present a timeline of records, and highlight, in each record those fields which have changed from the previous record. Wrote a solution in js in 2 mins which I hoped would run on a server, but now I am being asked to provide a solution client-side.

[Holger Steinhauer [Mod]]

If you change your state in only one place you can keep track of the changes. And yes, it sounds like Redux for a reason 😉