Observable within another Observable in RXJS is a powerful feature that

Here is the code snippet I have been working on:

return this.projectService.oneById(id).pipe(mergeMap(project => {
      if (!project) {
        return [];
      }

      const stories = this.getStories(id);

      return combineLatest(project.members.map(member => {
        return this.userService.one(member.id).pipe(map(memberData => {
          const assigned = stories.pipe(mergeMap(t => combineLatest(t.filter(task => {
            if (task && task.assignee?.id === member.id) {
              return {
                ...task,
                id: task.id
              };
            }
          }))));

          return {
            id: member.id,
            name: memberData?.displayName ?? 'Unknown',
            assigned
          };
        }));
      }));
    }));

Unfortunately, I am encountering an issue where my function is expected to return Observable<Type[]>, but it is currently providing

Observable<{ ...etc, object: Observable<Type[]> }
.

The core problem lies in the observable nested inside another observable. I have solved similar issues before in my code, but this one is proving to be quite challenging. I have tried various solutions without success.

I would greatly appreciate any assistance or guidance on resolving this matter.

PS: The specific warning message I am receiving is as follows:

Type 'Observable<{ id: string; name: string; assigned: Observable<[UserStory | undefined]>; }[]>' is not assignable to type 'Observable<Member[]>'.   Type '{ id: string; name: string; assigned: Observable<[UserStory | undefined]>; }[]' is not assignable to type 'Member[]'.     Type '{ id: string; name: string; assigned: Observable<[UserStory | undefined]>; }' is not assignable to type 'Member'.       Types of property 'assigned' are incompatible.         Type 'Observable<[UserStory | undefined]>' is missing the following properties from type 'UserStory[]': length, pop, push, concat, and 25 more.

Answer №1

There is a scenario where you are attempting to replace an observable with an array in an object field. The following code snippet could be improved:

return this.projectService.oneById(id).pipe(mergeMap(project => {
  if (!project) {
    return [];
  }
  const stories = this.getStories(id);

  return combineLatest(project.members.map(member => {
    return this.userService.one(member.id).pipe(map(memberData => {
      const assigned$ = stories.pipe(mergeMap(t => combineLatest(t.filter(task => {
        if (task && task.assignee?.id === member.id) {
          return {
            ...task,
            id: task.id
          };
        }
      }))));
      return assigned$.pipe(map(assigned => ({
       id: member.id,
       name: memberData?.displayName ?? 'Unknown',
       assigned
      })));
    }));
  }));
}));

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