MG
how can i make a function accept both an instance of a class and an instance of that classes supertype without requiring an overloaded function
Size: a a a
2019 October 08
AM
The first question you've asked and deleted was the key to the answer.
AL
Matthew Good
how can i make a function accept both an instance of a class and an instance of that classes supertype without requiring an overloaded function
Just do the function that accept supertype
Great examples from the standard library - extension functions for Iterable like map or filter
Great examples from the standard library - extension functions for Iterable like map or filter
MG
ok, why CANT a function accepting A, accept a class instance that has A as its supertype?
for example
for example
open class A() {}
class B: A() {}
fun a(v: A) {}
a(B())AM
https://pl.kotl.in/VrOcWIqP5
It works for me. What am I doing wrong?
It works for me. What am I doing wrong?
AM
Apart from the fact that
A should be open class or abstract class or interface in your example, as the code you've provided won't even compile.AM
This is exactly the reason why I asked if you've tested that yourself. As soon as you boil down your use-case to simple example, you are able to validate the idea.
MG
wtf why does yours work but mine fail?
https://pl.kotl.in/nrDhSZXee
for mine i get
https://pl.kotl.in/nrDhSZXee
for mine i get
Type mismatch: inferred type is VectorBase<Type> but VectorCore<Any> was expectedopen class VectorCore<Type> {}
open class VectorBase<Type>: VectorCore<Type> {
fun elementWiseOperation(vector: VectorCore<Any>, action: (result: VectorCore<Any>, lhs: Any, rhs: Any) -> Unit): VectorCore<Any> {}
fun t() {
val A = elementWiseOperation(this) {}
}
}AM
Try
Any? instead of Any.AM
Or
VectorCore<Type: Any> if you aren't going to work with nulls.AL
Matthew Good
wtf why does yours work but mine fail?
https://pl.kotl.in/nrDhSZXee
for mine i get
https://pl.kotl.in/nrDhSZXee
for mine i get
Type mismatch: inferred type is VectorBase<Type> but VectorCore<Any> was expectedopen class VectorCore<Type> {}
open class VectorBase<Type>: VectorCore<Type> {
fun elementWiseOperation(vector: VectorCore<Any>, action: (result: VectorCore<Any>, lhs: Any, rhs: Any) -> Unit): VectorCore<Any> {}
fun t() {
val A = elementWiseOperation(this) {}
}
}As we discussed before, for invariant generics VectorCore<Any> != VectorCore<Type>.
If it's applicable you can either provide covariance for generic type or provide different signature for elementWiseOperation function
If it's applicable you can either provide covariance for generic type or provide different signature for elementWiseOperation function
AM
As in general case
Generic<T> implicitly means Generic<T: Any?>, which is not a subtype of Generic<Any>.MG
ok
MG
so if a class should only deal with integers should null be reinterperated as 0 in get and set operators?
AM
You are free to decide what better suits your needs.
MG
in what use cases (in generics) would it be appropriate to allow an integer to be
nullD
получается что если класс FileHelper реализует интерфейс DataProvider то можно писать FileHelperImpl : DataProvider?
Продолжаю цепляться. 😁
Либо это
Либо wrapper, реализующий
У вас какой случай?
FileHelperImpl : DataProvider немного отдает.Либо это
FileHelper как контейнер для утилитных методов.Либо wrapper, реализующий
DataProvider<>.У вас какой случай?
AM
Ниже ж ответ.
MG
what if i used a Union or equivilant instead? would that be possible? or would the type need to be explicitly cast
as UnionClassD
Ниже ж ответ.
Ага, теперь понял. Но название тогда очень так-себе. :)