Interface TypeSafeKey<A,B>

Type Parameters:
A - The raw type of the value that this key maps to inside an HMap
B - The mapped type of the value that this key maps to inside an HMap
All Superinterfaces:
Applicative<A, Iso<A,?,B,B>>, Contravariant<A, Profunctor<?, A, Iso<?,?,B,B>>>, Functor<A, Iso<A,?,B,B>>, Iso<A,A,B,B>, Iso.Simple<A,B>, Monad<A, Iso<A,?,B,B>>, MonadRec<A, Iso<A,?,B,B>>, Optic<Profunctor<?,?,?>, Functor<?,?>, A, A, B, B>, Optic.Simple<Profunctor<?,?,?>, Functor<?,?>, A, B>, Profunctor<A, A, Iso<?,?,B,B>>
All Known Subinterfaces:
TypeSafeKey.Simple<A>
public interface TypeSafeKey<A,B> extends Iso.Simple<A,B>
An interface representing a parametrized key for use in HMaps. Additionally, every TypeSafeKey is an Iso from the type the value is stored as to the type it's viewed and set as (on the way in / on the way out). This allows multiple keys to map to the same value, but to view the value as different types.

This is intentionally an interface so user-defined implementations are possible; however, it's important to note that all hopes of type-safety hinge on equality being implemented such that no two TypeSafeKeys with differing value-type parameters may be considered equal. Reference equality is used here as the default, as that is sufficient.

  • Method Details

    • discardR

      default <U> TypeSafeKey<A,B> discardR(Applicative<U, Iso<A,?,B,B>> appB)
      Description copied from interface: Iso.Simple
      Sequence both this Applicative and appB, discarding appB's result and returning this Applicative. This is generally useful for sequentially performing side-effects.
      Specified by:
      discardR in interface Applicative<A,B>
      Specified by:
      discardR in interface Iso<A,A,B,B>
      Specified by:
      discardR in interface Iso.Simple<A,B>
      Specified by:
      discardR in interface Monad<A,B>
      Specified by:
      discardR in interface MonadRec<A,B>
      Type Parameters:
      U - the type of appB's parameter
      Parameters:
      appB - the other Applicative
      Returns:
      this Applicative

    • andThen

      default <C> TypeSafeKey<A,C> andThen(Iso.Simple<B,C> f)
      Left-to-right composition of this TypeSafeKey with some other Iso. Because the first parameter fundamentally represents an already stored value type, this is the only composition that is possible for TypeSafeKey, which is why only this (and not Iso.compose(Optic)) is overridden.

      Particularly of note is the fact that values stored at this key are still stored as their original manifest type, and are not duplicated - which is to say, putting a value at a key, yielding a new key via composition, and putting a new value at the new key still only results in a single entry in the HMap. Additionally, all previous keys involved in the new key's composition are still able to resolve the value in their native type.

      Specified by:
      andThen in interface Iso.Simple<A,B>
      Type Parameters:
      C - the new value type
      Parameters:
      f - the other simple iso
      Returns:
      the new TypeSafeKey

    • typeSafeKey

      static <A> TypeSafeKey.Simple<A> typeSafeKey()
      Static factory method for creating a simple type-safe key
      Type Parameters:
      A - the type of value stored at this key
      Returns:
      a unique type-safe key