Updating an element in a observable list

Thank you for this awesome library.

Reviewing your example https://react-rxjs.org/docs/tutorial/github-issues I can see that there’s a good example of requesting a list of items form https://api.github.com/repos/${org}/${repo}/issues?per_page=25&page=${page}.

currentRepoAndPage$ is a merge of 2 source observables currentRepo$ and pageSelected$. When any of these source Subjects emit a new value

 currentRepoAndPage$.pipe(
    switchMap(({ page, repo, org }) =>
      getIssues(org, repo, page).pipe(startWith(SUSPENSE))
    )
  )

will re-execute.

The question; if I had an observable with a list of issues and I wanted to update one of the issues in the list, what would this look like? Would I update the item in the list from the component and call a function to push the new list into the Subject?

I also wondered if we could use BehaviorSubject instead of Subject?

[josepot]

However worth noting I believe it introduces a higher level of complexity than using BehaviorSubjects. But maybe it’s just another way of approaching the problem that I’m less familiar with

This library wants to promote a mental model where we avoid mutating state directly, because the we want to be able to define the dynamic behavior of the state at the time of its declaration. Therefore, if we adhere to this mental model, then we should try to use Subjects only for capturing external events, not as a means for mutating the state. This is indeed a quite radical mental-shift, but based in our experience, this mental model ends-up generating code that’s less complex and easier to maintain.

I’m going to close this issue, because as you said, I have already answered your question. However, feel free to keep commenting on it after it’s closed. Thanks!

[sbitproz]

Hi @josepot

Totally grateful for message, on new years day no less…

I like the way you’ve approached the solution with streams. I’ve applied your todo example with my state solution - but now I think I might adapt a little more to my use case. However worth noting I believe it introduces a higher level of complexity than using BehaviorSubjects. But maybe it’s just another way of approaching the problem that I’m less familiar with.

Although I understand that BehaviorSubject cache’s the last emitted value, I’m not sure that will produce a leak. In reality it’s just single BehaviorSubject instance representing the state with a cache which will be overwritten.

I freely admit, it maybe be down to my lack of understanding of what’s going on under the hood.

You have answered my question and I’ve read most of the library documentation, just wanted to soundboard the idea (BehaviorSubject). Really appreciate your help.