distintUntilChanged: new overload missing in bundle #7475

Activity

1. conblem commented on Jun 26, 2024

   

   conblem

   on Jun 26, 2024

   More actions

   I am facing the same problem
2. al-mart commented on Aug 1, 2024

   

   al-mart

   on Aug 1, 2024

   Last edited by al-mart

   More actions

   If you analyze the source you will see

   export function distinctUntilChanged<T>(comparator?: (previous: T, current: T) => boolean): MonoTypeOperatorFunction<T>;
   export function distinctUntilChanged<T, K>(
     comparator: (previous: K, current: K) => boolean,
     keySelector: (value: T) => K
   ): MonoTypeOperatorFunction<T>;
   export function distinctUntilChanged<T, K>(
     comparator?: (previous: K, current: K) => boolean,
     keySelector: (value: T) => K = identity as (value: T) => K
   ): MonoTypeOperatorFunction<T>
   

   the first overload is just the comparator,
   the second one is the comparator and the key selector which means you can have two objects as T and property keys as K, which would be returned by the second argument which is the keySelector function.

   The third overload is the implementation
   The implementation signature must also be compatible with the overload signatures
   so in this case it is having a default value of identity which is a function returning the argument

   export function identity<T>(x: T): T {
     return x;
   }
   

   So in this case you don't need it actually
   And also that's how typescript work.

   Official typescript

   `
   Again, the signature used to write the function body can’t be “seen” from the outside.

   The signature of the implementation is not visible from the outside. When writing an overloaded function, you should always have two or more signatures above the implementation of the function.

   `
   Myself i would have the K as keyof T so that non existent keys are not passed but that would mess up the overloading.