How to Create Array of Unique Object List in Swift

How to create array of unique object list in Swift

As of Swift 1.2 (Xcode 6.3 beta), Swift has a native set type.
From the release notes:

A new Set data structure is included which provides a generic
collection of unique elements, with full value semantics. It bridges
with NSSet, providing functionality analogous to Array and Dictionary.

Here are some simple usage examples:

// Create set from array literal:
var set = Set([1, 2, 3, 2, 1])

// Add single elements:
set.insert(4)
set.insert(3)

// Add multiple elements:
set.unionInPlace([ 4, 5, 6 ])
// Swift 3: set.formUnion([ 4, 5, 6 ])

// Remove single element:
set.remove(2)

// Remove multiple elements:
set.subtractInPlace([ 6, 7 ])
// Swift 3: set.subtract([ 6, 7 ])

print(set) // [5, 3, 1, 4]

// Test membership:
if set.contains(5) {
    print("yes")
}

but there are far more methods available.

Update: Sets are now also documented in the "Collection Types" chapter of the Swift documentation.

Unique array of objects

You need to add this extension to return an ordered set from your people array.

extension Collection where Element: Hashable {
    var orderedSet: [Element] {
        var set: Set<Element> = []
        return reduce(into: []){ set.insert($1).inserted ? $0.append($1) : ()  }
    }
}

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You will also have to make your Person class Equatable:

func ==(lhs: Person, rhs: Person) -> Bool {
    return lhs.id == rhs.id
} 

class Person: Equatable { 
    let id: String 
    let name: String 
    init(id: String, name: String) { 
        self.id = id 
        self.name = name 
    } 
}

---

Testing

let person1 = Person(id: "1", name: "Adam") 
let person2 = Person(id: "1", name: "Adam") 
let person3 = Person(id: "2", name: "John") 
let person4 = Person(id: "2", name: "John") 
let person5 = Person(id: "3", name: "Michael") 
let person6 = Person(id: "4", name: "Nick") 
let person7 = Person(id: "5", name: "Tony") 
let people = [person1,person2,person3,person4,person5,person6,person7] 
people.orderedSet //[{id "1", name "Adam"}, {id "2", name "John"}, {id "3", name "Michael"}, {id "4", name "Nick"}, {id "5", name "Tony"}]

Unique Objects inside a Array Swift

You can use Swift Set:

let array = [product,product2,product3]

let set = Set(array)

You have to make Product conform to Hashable (and thus, Equatable) though:

class Product : Hashable {
    var subCategory = ""

    var hashValue: Int { return subCategory.hashValue }
}

func ==(lhs: Product, rhs: Product) -> Bool {
    return lhs.subCategory == rhs.subCategory
}

And, if Product was a NSObject subclass, you have to override isEqual:

override func isEqual(object: AnyObject?) -> Bool {
    if let product = object as? Product {
        return product == self
    } else {
        return false
    }
}

Clearly, modify those to reflect other properties you might have in your class. For example:

class Product : Hashable {
    var category = ""
    var subCategory = ""

    var hashValue: Int { return [category, subCategory].hashValue }
}

func ==(lhs: Product, rhs: Product) -> Bool {
    return lhs.category == rhs.category && lhs.subCategory == rhs.subCategory
}

get distinct elements in an array by object property

Hope this will help you:

class Item:Equatable, Hashable {
    var name: String
    init(name: String) {
        self.name = name
    }
    var hashValue: Int{
      return name.hashValue
    }

}

func ==(lhs: Item, rhs: Item) -> Bool {
    return lhs.name == rhs.name
}


let items = [Item(name:"1"), Item(name:"2"), Item(name:"1"), Item(name:"1"),Item(name:"3"), Item(name:"4")]

var uniqueArray = Array(Set(items))

getting unique items in an array

let uniqueList = nationalities.reduce([], {
    $0.contains($1) ? $0 : $0 + [$1]
})

How can I get array object of unique value using Higher Order Functions of swift

A solution with Dictionary(grouping:by:)

let array = [1, 2, 3, 1, 3, 4, 2, 1]
let output = Dictionary(grouping: array, by: {$0})
    .values
    .sorted(by: { $0[0] < $1[0] })

How to get the unique id's of objects in an array swift

You can use a Set to obtain only the unique values. I would suggest that you have your function return a Swift array rather than NSArray too.

func getUniqueIDsFromArrayOfObjects(events:[Event])->[String]
{
   let eventIds = events.map { $0.eventID!}
   let idset = Set(eventIds)
   return Array(idset)
}

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