How to make a dictionary data from Firestore conform to sequence? I want use one of the fields and add the Integers together

I have a compactmap of the the data from the cloud Firestore, however I need access to just one of the variables and iterate over it to add up the Integers stored there.
My data contains Dates and does not conform to Sequence and I am struggling to find a solution

My data:

struct Travel: Identifiable, Equatable, Codable {
    var id = UUID()
    var reason: String
    var date: Date
    var numDays: Int

Firestore fetch:

func fetchData() async throws -> [Travel] {
        guard let uid = Auth.auth().currentUser?.uid else { return [] }
        let snapshot = try await reference1.document(uid).collection("dates")
            .order(by: "date", descending: true)
            .getDocuments()
        return snapshot.documents.compactMap { document in
            try! document.data(as: Travel.self)
        }
    }

I need a way to access the numDays data and add together all the values for all the data saved.

I have tried for loops but as Travel doesn't conform to Sequence I cannot do that.

I then have the viewModel:

    @Published var travel: Loadable<[Travel]> = .loading
    
    
        func fetchPosts() {
                Task {
                    do {
                        travel = .loaded(try await datesRepository.fetchData())
                    } catch {
                        print("[ViewModel] Cannot fetch posts: \(error)")
                        travel = .error(error)
                    }
                }
            }

Any attempts to do a for loop on this data hasn't worked.
Please help

If I understand the problem correctly, you want to take an array of Travel objects, pull out the value of numDays and add all of them together? If so, you can use .reduce.

let travelArray: [Travel] = ...
let totalDays = travelArray.reduce(0) { $0 + $1.numDays }

This translates to "take your array and perform a reduce starting at 0, adding each Travel object's numDays value to the running total in reduce and return the total."

You can create a function that you pass in an array of your Travel objects and use the .reduce method to sum up the days and return it if you want. Something like this:

func calculateTotalNumDays(travels: [Travel]) -> Int {
    let totalNumDays = travels.reduce(0) { (result, travel) in
        return result + travel.numDays
    }
    return totalNumDays
}

//Example
do {
    let fetchedTravels = try await datesRepository.fetchData()
    let totalNumDays = calculateTotalNumDays(travels: fetchedTravels)
    print("Total numDays: \(totalNumDays)")
} catch {
    print("Error fetching data: \(error)")
}