Is there a way to to associate an enum with a sealed class i

Question

Is there a way to to associate an enum with a sealed class implementation Lets say you have a generic enum accessible in your entire project in my case I m working with types of mental health care and throughout your project sometimes per type we need a slightly different implementation Currently I have an Enum with Type1 Type2 and Type3 and then a sealed class with an implementation for every type Now I have a map in which I would like to give a key enum and then get back the specific implementation However I cannot guarantee that if you call the enummap with type1 key you get a value that represented type1 value

Joffrey · Answer

There is no language feature associating the values of an enum type to subtypes of a sealed class But it s possible to do this yourself depending on what you need You can for instance store the corresponding enum value as a property of the sealed class so you can find the instance with that value This would allow you to build your map automatically If you want the kind of type safety you described I wonder how you would use it in real life I mean if the enum value is known in advance `yourMap get YourEnum TYPE 1 ` then you could just build a correct instance of the sealed class s subclass right away instead However if you re using a dynamic enum value `yourMap get someEnumValueVariable ` you can t know at compile time which type of instance you will get anyway so there is no real point in enforcing that your map returns the specific subtype anyway Or did I miss something here

Joffrey · Answer

If you really really want this type safety you could use another sealed class instead of the enum with only `object`s as subtypes That sealed class would be generic and the type parameter would be the type of your original sealed class that you want this new one to represent ```sealed class Original data class ActualImpl1 Original data class ActualImpl2 Original this replaces your enum sealed class MyKey lt T Original gt object Type1 MyKey lt ActualImpl1 gt object Type2 MyKey lt ActualImpl2 gt ``` This would allow you to build your heterogeneous typesafe map but at this point I believe it might be better to use the original sealed class instead of the enum in more places smile

Michael de Kaste · Answer

the values are not objects sadly Per person worker registration etc per domain you can have a different version of an implementation meaning that the values of said map are data classes that are filled upon creation Currently what we are doing is just having all these classes that have the per domain information as loose vals in a class like so `class Workflow ` `val someData String` `val someMoreData String` `val type1Information Information Type1 = null` `val type2Information Information Type2 = null` `val type3Information Information Type3 = null` ` ` and then on creation we fill the known and desired information and can easily just access all the vals the problem is that the amount of types in our application is slowly growing as we are implementing more and more for our customers and therefor having littered values is bloating our code An EnumMap would provide the perfect solution I would think

Michael de Kaste · Answer

and at other times we have 2 classes with information for these types and we would like to know what the other class has for type1 for instance in order to request the specific values from these class Now it all needs to be done manually if I have these 2 sealed class informations and now on another spot for every type I need to request the data from these classes I need to do all kinds of manual checks in order to get the correct information If you get what I mean

Joffrey · Answer

gt the values are not objects sadly Per person worker registration etc per domain you can have a different version of an implementation meaning that the values of said map are data classes that are filled upon creation The `object`s in my suggestion were meant to replace the enum not the current sealed class hierarchy that you have The `Original` sealed class in my example would still be there and still have proper classes with data inside The idea of the second sealed class instead of the enum was to allow a type safe map access you seemed to want