Function combineLatestByKey

combineLatestByKey<Input extends Record<string, unknown>, R>(
    project: (
        source$: Observable<Input[Extract<keyof Input, string>]>,
        key: Extract<keyof Input, string>,
    ) => Observable<R>,
): OperatorFunction<Input, Record<Extract<keyof Input, string>, R>>
Dynamic counterpart to switchMap(() => combineLatest(...)) for records, with stable branches by key.

Each record key gets its own long-lived branch. Branches are only created/removed when keys are added/removed; value updates are pushed through the existing key branch.
Type Parameters
- Input extends Record<string, unknown>
- R
Parameters
- project: (
  source$: Observable<Input[Extract<keyof Input, string>]>,
  key: Extract<keyof Input, string>,
  ) => Observable<R>
Returns OperatorFunction<Input, Record<Extract<keyof Input, string>, R>>
- Defined in packages/core/src/observable/combine-latest-by-key.ts:14