2 replies

`effect-rx` Effect.orElse equivalent

I'm probably just fully misunderstanding effect-rx and doing something dumb here, but I'm struggling with the following:
- I'm using @effect/rpc to make requests to a single nextjs api route, which is working.
- I have a page that displays a list of "cases". I'm fetching it using rpcClient and storing it as an Rx so I can grab it using a hook. That's working. I'm also using a cache, so it looks like this:

const list = Rx.make((get) => cache.get(get(query)))

const list = Rx.make((get) => cache.get(get(query)))

- The query for fetching the list is also stored as an Rx, and I have functions for updating the query, so I can i.e. perform a search.
- I want a hook for the "single case" view that checks the array of cases and looks for it by ID. If it finds it, great, otherwise make a new request to fetch it from the server.

This is already a weird way to do this, but I'm trying to figure out rx at the same time, so I'm mostly relying on copying strategies from effect-ts/website and tim-smart/effect-rx-playground.

Here is the totally incorrect implementation of this function, with the return type I want to have annotated:

const casesRx = runtime.rx(() => Effect.gen(function*(){
// ... other defs ...

// no idea if Rx.family is necessary here
const fetchById = Rx.family((caseId: CaseId) =>
  Rx.make(client(new ShowCaseRequest({ caseId })))
);

// wrong, but I'm unsure what to do here
const show = <E>(caseId: CaseId): Rx.Rx<Result.Result<Case, E>> =>
Rx.make((get) =>
  pipe(
    Rx.mapResult(list, (cases) =>
      Array.findFirst(cases, (case_) => case_.id === caseId)
    ),
    Rx.map((result) => {
      Result.matchWithError(result, {
        onInitial: () => Result.initial(),
        onSuccess: (result) =>
          Option.match(result.value, {
            onNone: () => Result.fail(new NoSuchElementException()),
            onSome: (case_) => Result.success(case_),
          }),
        onError: () => get(fetchById(caseId)),
        onDefect: () => get(fetchById(caseId)),
      });
    })
  )
);

const casesRx = runtime.rx(() => Effect.gen(function*(){
// ... other defs ...

// no idea if Rx.family is necessary here
const fetchById = Rx.family((caseId: CaseId) =>
  Rx.make(client(new ShowCaseRequest({ caseId })))
);

// wrong, but I'm unsure what to do here
const show = <E>(caseId: CaseId): Rx.Rx<Result.Result<Case, E>> =>
Rx.make((get) =>
  pipe(
    Rx.mapResult(list, (cases) =>
      Array.findFirst(cases, (case_) => case_.id === caseId)
    ),
    Rx.map((result) => {
      Result.matchWithError(result, {
        onInitial: () => Result.initial(),
        onSuccess: (result) =>
          Option.match(result.value, {
            onNone: () => Result.fail(new NoSuchElementException()),
            onSome: (case_) => Result.success(case_),
          }),
        onError: () => get(fetchById(caseId)),
        onDefect: () => get(fetchById(caseId)),
      });
    })
  )
);

What do I need to do instead?

`effect-rx` Effect.orElse equivalent

const list = Rx.make((get) => cache.get(get(query)))

const list = Rx.make((get) => cache.get(get(query)))

const casesRx = runtime.rx(() => Effect.gen(function*(){
// ... other defs ...

// no idea if Rx.family is necessary here
const fetchById = Rx.family((caseId: CaseId) =>
  Rx.make(client(new ShowCaseRequest({ caseId })))
);

// wrong, but I'm unsure what to do here
const show = <E>(caseId: CaseId): Rx.Rx<Result.Result<Case, E>> =>
Rx.make((get) =>
  pipe(
    Rx.mapResult(list, (cases) =>
      Array.findFirst(cases, (case_) => case_.id === caseId)
    ),
    Rx.map((result) => {
      Result.matchWithError(result, {
        onInitial: () => Result.initial(),
        onSuccess: (result) =>
          Option.match(result.value, {
            onNone: () => Result.fail(new NoSuchElementException()),
            onSome: (case_) => Result.success(case_),
          }),
        onError: () => get(fetchById(caseId)),
        onDefect: () => get(fetchById(caseId)),
      });
    })
  )
);

const casesRx = runtime.rx(() => Effect.gen(function*(){
// ... other defs ...

// no idea if Rx.family is necessary here
const fetchById = Rx.family((caseId: CaseId) =>
  Rx.make(client(new ShowCaseRequest({ caseId })))
);

// wrong, but I'm unsure what to do here
const show = <E>(caseId: CaseId): Rx.Rx<Result.Result<Case, E>> =>
Rx.make((get) =>
  pipe(
    Rx.mapResult(list, (cases) =>
      Array.findFirst(cases, (case_) => case_.id === caseId)
    ),
    Rx.map((result) => {
      Result.matchWithError(result, {
        onInitial: () => Result.initial(),
        onSuccess: (result) =>
          Option.match(result.value, {
            onNone: () => Result.fail(new NoSuchElementException()),
            onSome: (case_) => Result.success(case_),
          }),
        onError: () => get(fetchById(caseId)),
        onDefect: () => get(fetchById(caseId)),
      });
    })
  )
);

What do I need to do instead?

`effect-rx` Effect.orElse equivalent

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