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

Question

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"))

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"}]

    }

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.