Hey guys, I have a really random question that’s k...

# random

[smilecs]

Hey guys, I have a really random question that’s kinda bugging me, is it really necessary to wrap a SharedPreference operation with a Rx call?
kinda something like

fun save(key: String, value: String) {
        sharedPreferences.edit().putString(key, value).apply()
    }

    fun saveSingle(key: String, value: String): Single<String> = Single.create {
        try {
            save(key, value)
            it.onSuccess(value)
        } catch (e: Exception) {
            it.onError(Failure.Error(e.localizedMessage))
        }
    }

[gildor]

it’s necessary only if you want to have Rx interface for this function

[smilecs]

ok, thanks not sure I would though

[gildor]

But this implementation doesn’t make a lot of sense, because apply() is asynchronous save, so you even don’t know when it actually happened. commit() makes a bit more sense, but it’s blocking operation so you probably done it on IO scheduler

[smilecs]

excellent thanks

[gildor]

Also instead of Single.create you can just use Single.fromCallable, which is mostly the same, but without wrapping to Failure.Error

[gildor]

also I believe such wrapping to Failure.Error is bad style, because you lose stack trace and cause of exception

[smilecs]

never knew about the Single.fromCallable will check it out as well

[gildor]

This is just static builder function that wraps any blocking code to Rx primitives like Single. Emits onNext or onError if code inside of builder throws an exception

[smilecs]

wow, thanks very much

[dewildte]

Shared preferences is basically a fancy wrapper for a big Map (over simplification I know) so it can be used from the main thread without issue.

That said though it is not a database so be very careful with how much you store in it.