Append string element from class to array of strings

Question

I have class in which have variable hall and other variables. I need to need pull out and add variable hall in new array of strings.

All variables are now stored in a variable with type BookingHall.

How do I get and add a variable hall to a new variable?

For everything I use firestore.

My class implementation:

protocol BookingDocumentSerializable {

    init?(dictionary: [String:Any])

}

struct BookingHall {

    var contactInfo: [String: Any] = [:]
    ................
    var hall: String = ""

    var dictionary: [String: Any] {

        return [

            "contact_info": contactInfo,
            ................
            "hall": hall

        ]
    }
}

extension BookingHall: BookingDocumentSerializable {

    init?(dictionary: [String: Any]) {

        let contactInfo = dictionary["contact_info"] as? [String: Any] ?? [:]
        ................
        let hall = dictionary["hall"] as? String ?? ""

        self.init(contactInfo: contactInfo,
                  ................
                  hall: hall)

    }
}

Here i get all variable in class:

var hallArray: [String] = []

private var historyBooking: [BookingHall] = []

fileprivate func observeQuery() {

    guard let query = query else { return }

    listener = query.addSnapshotListener { [unowned self] (snapshot, error) in

        if let snapshot = snapshot {

            let bookingModel = snapshot.documents.map { (document) -> BookingHall in

                if let newHistoryBooking = BookingHall(dictionary: document.data()) {

                    return newHistoryBooking

                } else {

                    fatalError("Ошибка загрузки!")

                }
            }

            self.historyBooking = bookingModel
            self.document = snapshot.documents

            for index in 0...self.historyBooking.count {

                self.hallArray.append(self.historyBooking[index].hall)

                print("hall id \(self.hallArray)")

            }

            self.tableView.reloadData()

        }
    }
}

In here I get error index out of range, but in console I can see hall id.

self.hallArray.append(self.historyBooking[index].hall)

How do I correctly add hall to a new array of strings in...

var hallArray: [String] = []

vadian · Accepted Answer · 2018-03-27 07:23:47Z

2

A very common mistake.

Indexes are zero-based. Imagine your array has one element. The range 0...array.count has the indexes 0 and 1 but there is no element at index 1...

You have to write either

for index in 0..<self.historyBooking.count

or

for index in 0...self.historyBooking.count - 1

The first syntax is preferable.

answered Mar 27, 2018 at 7:23

vadian

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1 Comment

Дмитрий Деникаев Over a year ago

Thank you for the detailed answer. I hope now I will no longer get this error.

Mahendra · Accepted Answer · 2018-03-27 07:24:33Z

0

To avoid Index out of bound you can use for...in loop

for obj in 0...self.historyBooking.count {

  self.hallArray.append(obj.hall)

  print("hall id \(self.hallArray)")

}

answered Mar 27, 2018 at 7:24

Mahendra

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