How to query more records and process them with Vapor?

Question

More Ids are received by router in a JSON. A query need to execute for each Id. Then do some manipulation of the original data and return it. But I get some error. And how to manage Futures? Each query will return a unique future? I need to check when all Futures finished? Do I need to use DispathGroup, or how?

I made like this:

router.post([Page].self, at: "/releases") { (request, pages) -> [Page] in
    for page in pages {
        for event in page.events {
            let release = Release.query(on: request).filter(\.fbId == event.id).first().flatMap { (release) -> EventLoopFuture<Release?> in
                return request.future(release)
            }
            if let release2 = release {
                event.started = release2.started
            }
        }
    }
    return pages
}

But it raise some error:

---

used following JSON:

[
    {
        "id": "107120697426006",
        "name": "Teszt Színház",
        "events": [
            {
                "id": "802128100247740",
                "name": "Teszt Esemény"
            },
            {
                "id": "1378145475685730",
                "name": "Teszt Esemény 2"
            }
        ]
    }
]

Answer 1

Something like that should work

router.post([Page].self, at: "/releases") { (req, pages) -> Future<[Page]> in
    var result: [Page] = []
    return pages.map { p in
        var page = p
        var pageEvents: [Event] = []
        return page.events.map { e in
            var event = e
            return Release.query(on: req).filter(\.fbId == event.id).first().map { release in
                if let release = release {
                    event.started = release.started
                }
                pageEvents.append(event)
            }
        }.flatten(on: req).map {
            page.events = pageEvents
            result.append(page)
        }
    }.flatten(on: req).transform(to: result)
}

or with one database call would be better

import FluentSQL // for `~~` operator

router.post([Page].self, at: "/releases") { (req, pages) -> Future<[Page]> in
    let eventIds = pages.map { $0.events }.flatMap { $0 }.map { $0.id }
    return Release.query(on: req).filter(\.fbId ~~ eventIds).all().map { releases in
        var result: [Page] = []
        for p in pages {
            var page = p
            var pageEvents: [Event] = []
            for e in p.events {
                var event = e
                if let release = releases.first(where: { $0.fbId == e.id }) {
                    event.started = release.started
                }
                pageEvents.append(event)
            }
            page.events = pageEvents
            result.append(page)
        }
        return result
    }
}