How to order by number of items with sectioning through relationships

[tiendq]

Example is from here.

Sections are ordered ascending by list title, how to order sections by their item count?

@FetchAll(
  Reminder
    .order(by: \.title)
    .join(RemindersList.all) { $0.remindersListID.eq($1.id) }
    .select { reminder, _ in reminder },
  sectionBy: { _, remindersList in remindersList.title.asc() }
)
var reminders

Thanks,

[mbrandonw]

Hi @tiendq, I'm not sure I understand how this grouping is supposed to work. You want to group reminders by their title and then order those sections by how many reminders are in each section? So something like this:

Personal
---------
Reminder1
Reminder2
Reminder3
Reminder4

Business
---------
Reminder5
Reminder6
Reminder7

Urgent
---------
Reminder8

?

[tiendq]

Yes, it is. I want to order sections by count of their items.

[mbrandonw]

That's a tough one. The sectioning API isn't really built for sectioning by one thing and ordering by a different thing. We just made the assumption that they thing you are sectioning by will be the thing you want to order by. We would need the ability to prepend another ordering clause before title, and I'm not sure what the API would look like.

I think right now your best bet is to do the sorting in memory using a custom FetchKey. Do not do the sorting directly in a SwiftUI view like the AI spam below recommended. That will re-sort every time the view re-renders, whereas a FetchKey will just do it once.

[tiendq]

@mbrandonw thank you, I tried several ways last week and my solution was an extra table to keep count values which handled by several SQL triggers. It looks good since I just still need one sectioned query, same as before.

Unfortunately, later today I found that in the ForEach loop section.name now is count value and not reminder list name :D 👯

Might be I need to look at your suggestion "using custom FetchKey" now, what is it exactly?

[tiendq]

Thanks but my question was about getting it done in SQLite e.g. ORDER BY COUNT(*).