Swift: Filter nested arrays

Question

I'm trying to filter an array of Deals with a status DealStaus which has a nested array of Bookings, each one with a BookingStatus. I want to filter Deals with status .won and Bookings according to the statuses given when calling the function. BookingStatus and DealStatus are both enums. Deal and Booking look like this:

public struct Deal: Decodable {
    public let identifier: String?
    public let status: DealStatus
    public let bookings: [Booking]?
}

public struct Booking: Decodable {
    public let identifier: String?
    public let status: BookingStatus
    public let startDate: Date?
    public let endDate: Date?
}

To do so I wrote the following snippet:

private func getDeals(with bookingStatus: [BookingStatus]) -> [Deal] {
    guard let user = currentUser, let deals = user.deals else { return [Deal]() } // Note: user is a class attribute

    return deals.filter { $0.status == .won && $0.bookings?.filter { bookingStatus.contains($0.status) }}

}

This does not work. The compiler gives the following error:

Optional type '[Booking]?' cannot be used as a boolean; test for '!= nil' instead

$0.bookings?.filter { bookingStatus.contains($0.status) } is an array. What is needed here is a Boolean, i,e, true or false. — matt
– matt, Commented Aug 14, 2018 at 12:12
You are trying to be too compact. Filter your Deals. Stop. Then, operating on that array of Deals, map to get a new array of Deals with their bookings filtered. Stop. Now return that new array. — matt
– matt, Commented Aug 14, 2018 at 12:16
Or create a function in Deal that does the check and returns a boolean so you could call ... && $0.checkBookings(bookingStatus) — Joakim Danielson
– Joakim Danielson, Commented Aug 14, 2018 at 12:32
For more help, show code! Show definitions of Deal and DealStatus and Booking and BookingStatus. — matt
– matt, Commented Aug 14, 2018 at 12:48

gmoraleda · Accepted Answer · 2018-08-14 13:21:19Z

5

Following the instructions of @matt, I broke it down:

private func getDeals(with bookingStatus: [BookingStatus]) -> [Deal] {
    guard let user = currentUser, let deals = user.deals else { return [Deal]() }
        return deals
            .filter { $0.status == .won }
            .filter { $0.bookings?.contains(where: { bookingStatus.contains($0.status)} ) ?? false }
    }

answered Aug 14, 2018 at 13:21

gmoraleda

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