Using a when clause in an enum class getter in Kotlin - enums

Question

I'm trying to get a specific getter of a property in kotlin to be based on the value of the enum it is called from. This is what I got so far:
enum class Endpoint {
EVENTS, GAMES;
val baseUrl = "https://www.example.com/api"
val path: String
get() = when(this){
EVENTS -> "$baseUrl/events"
GAMES -> "$baseUrl/games"
}
}
Called like this:
print(Endpoint.EVENTS.path)
While this compiles without any problem, as soon as I run it I get a NullPointerException with the error Attempt to invoke virtual method 'java.lang.Object [...].Endpoint[].clone()' on a null object reference
I'm not sure what I'm doing wrong or what the proper way to accomplish what is stated above is.
EDIT: Full log of the exception:
05-09 22:51:33.793 15673-15673/com.filippovigani.eventvods E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.filippovigani.eventvods, PID: 15673
java.lang.ExceptionInInitializerError
at com.filippovigani.eventvods.networking.Endpoint.getPath(Endpoint.kt:21)
at com.filippovigani.eventvods.networking.Endpoint.<init>(Endpoint.kt:25)
at com.filippovigani.eventvods.networking.Endpoint.<clinit>(Endpoint.kt)
at com.filippovigani.eventvods.networking.EventvodsApi$Companion.getEvents(EventvodsApi.kt:8)
at com.filippovigani.eventvods.MainActivity.onCreate(MainActivity.kt:19)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object com.filippovigani.eventvods.networking.Endpoint[].clone()' on a null object reference
at com.filippovigani.eventvods.networking.Endpoint.values(Endpoint.kt)
at com.filippovigani.eventvods.networking.Endpoint$WhenMappings.<clinit>(Unknown Source)
at com.filippovigani.eventvods.networking.Endpoint.getPath(Endpoint.kt:21) 
at com.filippovigani.eventvods.networking.Endpoint.<init>(Endpoint.kt:25) 
at com.filippovigani.eventvods.networking.Endpoint.<clinit>(Endpoint.kt) 
at com.filippovigani.eventvods.networking.EventvodsApi$Companion.getEvents(EventvodsApi.kt:8) 
at com.filippovigani.eventvods.MainActivity.onCreate(MainActivity.kt:19) 
at android.app.Activity.performCreate(Activity.java:5990) 
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
at android.app.ActivityThread.access$800(ActivityThread.java:151) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:135) 
at android.app.ActivityThread.main(ActivityThread.java:5254) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 

Answer 1

I can't reproduce your error, the code works fine. Nevertheless, I think the solution is a bit too complex, why don't you use a constructor argument to provide the constant-specific value:
enum class Endpoint(service: String) {
EVENTS("/events"), GAMES("/games");
private val baseUrl = "https://www.example.com/api"
val path: String = baseUrl + service
}

Answer 2

The exception indicates you're trying to access path within the constructor of the enum. This causes a problem because the enum is not yet ready for use during construction.
This means the following chain of calls results in failure:
Init Endpoint
Init Endpoint.EVENTS
Call to Endpoint.getPath() (This does not show in your code)
Uses Endpoint$WhenMapping, begin init of that class.
Endpoint$WhenMapping uses EndPoint.values(), but since we're still initializing the instances of the enum, the values array cannot be provided, returning null.
To ensure it is not modified, WhenMapping clones and caches the array, but since the array is null when it never should be outside of initialization this causes the NPE.
Simply put your code somehow relies on a class that requires itself to be fully initialized to use. Since your code does not display how you're calling Endpoint.EVENTS.path this is all that can be said about it.