循环对象数组并显示项目，而无需复制它们

Question

i have an array of object which has region and city.. these region and city can be repeated in more than one object ..

i want to loop on them and display these regions and cities without duplicating them ...

how can i do this?

this is the class:

  struct Shifts : Decodable{
let id: Int
let region: String
let city: String
let nationality: String
let idService: Int
let shiftDate: String
let shiftType: String
let weekday: String
let quantityStaff: Int
let leadHours: Int
let createdAt: String?
let updatedAt: String?
let deletedAt: String?
}

example of the array:

shift=[(id: 1, region: Eastern, city: Dammam, nationality: Saudi, idService: 1, shiftDate: 11-12-2019, shiftType: day, weekday: sat, quantityStaff: 1, leadHours: 7),(id:2, region: eastern, city: dhahran, nationality: saudi, idService: 2, shiftDate: 22-1-12018, shiftType: full, weekday: mon, quantityStaff: 2, leadHours: 4)]

both shifts are in region eastern .. so i don't want to display eastern twice for the user...

i will display them in a tableview as dropdown list so the user can select from it .. and i don't want to repeat it for them .. i only want to display it once.

Answer 1

You could use a set to filter Shifts with unique regions:

let myShifts = [Shifts]()
//populate your myShifts array.

func filteredShifts() -> [Shifts] {

    var regions = Set<String>()

    let filteredShifts = myShifts.filter {

      if !regions.contains($0.region) {
        regions.insert(aShift.region)
        return true
      } else { return false }
    }
    return filteredShifts
}

Answer 2

struct Shifts : Decodable{
    let id: Int
    let region: String
    let city: String
    let nationality: String
    let idService: Int
    let shiftDate: String
    let shiftType: String
    let weekday: String
    let quantityStaff: Int
    let leadHours: Int
    let createdAt: String?
    let updatedAt: String?
    let deletedAt: String?
}

struct Area: Hashable{
    var region : String
    var city : String

    var hashValue: Int {
        return "(\(region),\(city))".hashValue
    }

    static func == (lhs: Area, rhs: Area) -> Bool {
        return lhs.region == rhs.region && lhs.city == rhs.city
    }
}

let shiftsArr = [Shifts]()

var seen = Set<Area>()
var unique = [Shifts]()
for shift in shiftsArr {
    let area = Area(region: shift.region, city:shift.city)
    if !seen.contains(area) {
        unique.append(shift)
        seen.insert(area)
    }
}

let areas = unique.map{
    return Area(region: $0.region, city: $0.city)
}