This is probably wrong but how can I fix it without using ko

Question

This is probably wrong but how can I fix it without using kotlin reflect ``` ExperimentalStdlibApi inline operator fun lt reified T Any gt SharedPreferences getValue owner Any property KProperty lt gt T return when val type = typeOf lt T gt is Set lt gt gt getStringSet property name replace emptySet emptySet else gt error Invalid type as T ```

Joffrey · Answer

Wrong in which way

dave08 · Answer

`typeOf lt T gt ` is a `KType` whereas `is` I think only works with actual instances

dave08 · Answer

`someobjinstance is Set lt gt `

Joffrey · Answer

Oh sorry I thought you meant wrong as in the working but wrong approach

Joffrey · Answer

What s your goal here Are you trying to implement a generic property delegate for all types of preferences

dave08 · Answer

Only certain types basically String Set lt String gt and Map lt String Set lt String gt gt which is build on delimited result of getStringSet and the property name is the name of the preference more or less

Joffrey · Answer

I mean it can probably be done with `KType isSubtypeOf`but that will require kotlin reflect I wonder if it s really necessary to have it generic instead of have a separate delegate for each independent type It doesn t seem much more inconvenient to declare `val x by stringPreference ` and `val x by stringSetPreference `

Joffrey · Answer

If you re ok with exact matches you can also use ```when val type = typeOf lt T gt typeOf lt Set lt String gt gt gt TODO else gt TODO ``` But I m not sure this is reliable

dave08 · Answer

it has a receiver of SharedPreferences since I have a few possible implementations of SharedPreferences so it would be `stringSetPreference prefs ` not as nice though What do you mean by exact matches And why shouldn t it be reliable I really only have those 3 types

dave08 · Answer

Seems to work like a charm ```import kotlin reflect typeOf inline fun lt reified T Any gt c = when val type = typeOf lt T gt typeOf lt String gt gt 1 typeOf lt Int gt gt 2 typeOf lt Set lt String gt gt gt 3 typeOf lt Set lt Int gt gt gt 4 else gt error something else $ type class val num Any = 0 fun main println c lt String gt println c lt Int gt println c lt Set lt String gt gt println c lt Set lt Int gt gt Gives 1 2 3 4```

dave08 · Answer

Thanks smiley It seems to work great even though it give a warning about when returning Any ``` ExperimentalStdlibApi inline operator fun lt reified T Any gt SharedPreferences getValue owner Any property KProperty lt gt T val keyName = property name replace return when typeOf lt T gt typeOf lt Set lt String gt gt gt getStringSet keyName emptySet lt String gt emptySet lt String gt typeOf lt String gt gt getString keyName else gt error Invalid type as T ```

Joffrey · Answer

gt What do you mean by exact matches gt I meant no supertypes are allowed for `T` with this approach so for instance a `CharSequence` property won t match the `String` case But for your use case it might be enough gt And why shouldn t it be reliable gt This is just a disclaimer because I have not looked at how `KType` s equality works It may work perfectly fine I just haven t checked

Joffrey · Answer

gt it has a receiver of SharedPreferences since I have a few possible implementations of SharedPreferences so it would be `stringSetPreference prefs ` not as nice though Ah I see so you want to simply delegate to `prefs` like `Map` does Makes sense You could also design it to work with the syntax `by prefs string ` `by prefs stringSet ` etc

dave08 · Answer

It seems like `typeOf ` returns a `TypeReference` and has ``` override fun equals other Any Boolean = other is TypeReference amp amp classifier == other classifier amp amp arguments == other arguments amp amp isMarkedNullable == other isMarkedNullable```

dave08 · Answer

But anyways it seems to work for all my current requirements

Raymond · Answer

< dave08> check this It might help Disclaimer It s old and definitely not the best approach for preferences specially nowadays