Change variable of all elements inside an array if Set contains it - ios

Question

I know this is a silly question but I don't know which will be the more performant solution. I have an array of ListItem. ListItem has a boolean value isSelected. I also have Set<ListItem>. I want to change that boolean to true if array has an element which is also inside Set. How can I achieve this with the best performance?
My Set and Array:
var selectedItems = Set<ListItem>()
var array: [ListItem] = []
List Item:
class ListItem: Codable ,Equatable, Hashable {
let wrapperType: String
let kind: String?
let trackId: Int?
let artistId: Int?
let collectionId: Int?
let artistName, collectionName, trackName: String?
let trackViewUrl: String?
let artworkUrl30, artworkUrl60,artworkUrl100: String?
let releaseDate: String?
let primaryGenreName: String?
var isSelected: Bool = false
enum CodingKeys: String, CodingKey {
case wrapperType, kind
case artistId
case collectionId
case trackId
case artistName, collectionName, trackName
case trackViewUrl
case artworkUrl30, artworkUrl60, artworkUrl100, releaseDate, primaryGenreName
}
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
wrapperType = try container.decode(String.self, forKey: .wrapperType)
print(wrapperType)
kind = try container.decodeIfPresent(String.self, forKey: .kind)
trackId = try container.decodeIfPresent(Int.self, forKey: .trackId)
collectionId = try container.decodeIfPresent(Int.self, forKey: .collectionId)
artistId = try container.decodeIfPresent(Int.self, forKey: .artistId)
artistName = try container.decodeIfPresent(String.self, forKey: .artistName)
collectionName = try container.decodeIfPresent(String.self, forKey: .collectionName)
trackName = try container.decodeIfPresent(String.self, forKey: .trackName)
trackViewUrl = try container.decodeIfPresent(String.self, forKey: .trackViewUrl)
artworkUrl30 = try container.decodeIfPresent(String.self, forKey: .artworkUrl30)
artworkUrl100 = try container.decodeIfPresent(String.self, forKey: .artworkUrl100)
artworkUrl60 = try container.decodeIfPresent(String.self, forKey: .artworkUrl60)
releaseDate = try container.decodeIfPresent(String.self, forKey: .releaseDate)
primaryGenreName = try container.decodeIfPresent(String.self, forKey: .primaryGenreName)
}
static func ==(lhs: ListItem, rhs: ListItem) -> Bool {
return lhs.trackName == rhs.trackName
}
func hash(into hasher: inout Hasher) {
if trackId != nil {
hasher.combine(trackName)
} else if collectionId != nil {
//AudioBooks Doesn't have TrackId
hasher.combine(collectionId)
} else {
print("Both TrackId && Collection Id is null")
}
}
}

Answer 1

Because these are reference types, if it is guaranteed that there is only one instance of any unique ListItem, it would be sufficient to just set isSelected to false for each item in your array, and then set isSelected to true for each item in your selectedItems.
array.forEach { $0.isSelected = false }
selectedItems.forEach { $0.isSelected = true }
If there can be more than one instance of an item, you are going to have to iterate the items in your array and check if the Set contains them. Fortunately, contains is O(1) for a Set:
array.forEach { $0.isSelected = selectedItems.contains($0) }
Note: It is vital that the hashValue be equal for ListItems that are equal, or this all breaks down. Your hash(into:) function is currently using more fields than your == function, so it is possible to generate a different hashValue for equal ListItems. Fix this to ensure that a proper hashValue is generated.