afternoon mark, nice to see you

hello, Eric~!

er, give or take a ~

how can I help you today?

when should I create a new viewmodel as opposed to using an existing one?

do you mean a viewmodel *class* or a viemodel *instance*?

good question. I meant class but I would be curious to know about instance as well

well, the answer to "instance" is: you shouldn't be creating instances of your viewmodel, most likely :-)

I am assuming that you are working with the Jetpack ViewModel system

most of the time, the Jetpack or your dependency inversion framework (e.g., Hilt, Koin) will create your viewmodel instances for you

in terms of when to create a new viewmodel class, my default tends to be "one per screen", with variations in cases where I might have some reuse that might work better with a reusable viewmodel

if I have a master detail view, should I use one or two viewmodels?

my gut instinct would be two, but I have not had to deal with master-detail in many years

(though that sort of large-screen UI is something I hope to get back into later this year)

I read that you want to use a shared viewmodel if you want fragment to fragment communication. So I opted to use a single viewmodel

that can work

it might also be that you wind up with 3 viewmodels: one for each of the fragments plus the shared activity-level one

as I learn I'm trying to make sure I adopt best practice

basically, while it's possible to have too much of a good thing, do not be afraid to create new viewmodel classes, particularly where the scope changes

yes

overall, though, I don't know that we have come to universal agreement on what the "best practices" are in this area

cool I appreciate it

if you have another question, go right ahead!

Do you know if there's a kotlin or rxjava function for this? I have a list of StudentDetail and a dean's list. Both contain an id. I want a new list of StudentDetail but only if its id was on a dean's list. It's kind of like a filter but I uses lists instead

students.filter { deansList.contains(it) } or something like that should give you what you want

or students.filter { deansList.contains(it.id) }

it depends a bit on what your classes all are structured like, but filter() is the right Kotlin function

if you need to do this in an RxJava chain, that would be a map() operator that takes the list and returns the filtered list, using the Kotlin filter() function

ok. You answered my questions. I appreciate it mark

happy to help!

enjoy your weekend, bye