How do I create a Set of custom objects (Swift)? - ios

Question

For my iOS app I have a model something like
class Person {
var Id: Int
var Name: String
init(id: Int, name: String?) {
self.Id = id
self.Name = name ?? ""
}
}
Then later on in my ViewController when I load data from the server I add some people to an array
class ViewController: UIViewController {
var people:[Person] = []
override func viewDidLoad() {
self.loadPeople()
}
func loadPeople() {
// This data will be coming from a server request
// so is just sample. It could have users which
// already exist in the people array
self.people.append(Person(id: "1", name: "Josh"))
self.people.append(Person(id: "2", name: "Ben"))
self.people.append(Person(id: "3", name: "Adam"))
}
}
What I am now trying todo is turn the people array into a Set<Person> so it will not add duplicates. Is this possible to do or do I need to change my logic?

Answer 1

To make set of Person you need to make it conform to Equatable and Hashable protocols:
class Person: Equatable, Hashable {
var Id: Int
var Name: String
init(id: Int, name: String?) {
self.Id = id
self.Name = name ?? ""
}
var hashValue: Int {
get {
return Id.hashValue << 15 + Name.hashValue
}
}
}
func ==(lhs: Person, rhs: Person) -> Bool {
return lhs.Id == rhs.Id && lhs.Name == rhs.Name
}
Then you can use set of persons like this:
var set = Set<Person>()
set.insert(Person(id: 1, name: "name"))

Answer 2

With Swift 2.0, Hashable and Equitable is a part of NSObject. All you need to do is to override "isEqual" and "var hash:" for the property of interest. In this case: "Id", Set will exclude Person-objects with identical Ids.
class Person: NSObject {
var Id: Int
var Name: String
init(id: Int, name: String?) {
self.Id = id
self.Name = name ?? ""
}
override var hash: Int {
return Id.hashValue
}
override func isEqual(object: AnyObject?) -> Bool {
guard let rhs = object as? Person else {
return false
}
let lhs = self
return lhs.Id == rhs.Id
}
}
func mergeArrays(){
let person1 = Person(id: 1, name: "Tom")
let person2 = Person (id: 2, name: "John")
let person3 = Person(id: 3, name: "Adam")
let downloadedPeople = [person1,person2] //[{NSObject, Id 1, Name "Tom"}, {NSObject, Id 2, Name "John"}]
let peopleStoredLocally = [person1,person3] //[{NSObject, Id 1, Name "Tom"}, {NSObject, Id 3, Name "Adam"}]
let downloadedPeopleSet = Set(downloadedPeople) //{{NSObject, Id 2, Name "John"}, {NSObject, Id 1, Name "Tom"}}
let mergedSet = downloadedPeopleSet.union(peopleStoredLocally) //{{NSObject, Id 2, Name "John"}, {NSObject, Id 3, Name "Adam"}, {NSObject, Id 1, Name "Tom"}}
let mergedArray = Array(mergedSet)//[{NSObject, Id 2, Name "John"}, {NSObject, Id 3, Name "Adam"}, {NSObject, Id 1, Name "Tom"}]
}

Answer 3

UPDATE
Depretation warning when using hashValue:
'Hashable.hashValue' is deprecated as a protocol requirement; conform
type 'Person' to 'Hashable' by implementing 'hash(into:)' instead
Following the object Person example, nowadays implementation would be:
class Person: Equatable, Hashable {
let id: Int
let countryId: Int
var name: String
init(id: Int, countryId: Int, name: String) {
self.id = id
self.countryId = countryId
self.name = name
}
func hash(into hasher: inout Hasher) {
hasher.combine(id)
hasher.combine(countryId)
}
static func == (lhs: Person, rhs: Person) -> Bool {
return lhs.id == rhs.id && lhs.countryId == rhs.countryId
}
}
Note: As per documentation the components used for hashing must be the same as the components compared in your type’s == operator implementation.