Swift 3.0 Remove duplicates in Array of Dictionari

Question

I am working removing the duplicate Dictionaries in an array of Dictionaries in swift 3.0

The below is the

let Dict1 : [String : String] = ["messageTo":"Madhu"]
let Dict2 : [String : String] = ["messageTo":"Kiran"]
let Dict3 : [String : String] = ["messageTo":"Raju"]

var arrOfDict = [[String:String]]()
arrOfDict.append(Dict1)
arrOfDict.append(Dict2)
arrOfDict.append(Dict1)
arrOfDict.append(Dict3)
arrOfDict.append(Dict2
print(arrOfDict)

//prints [["messageTo": "Madhu"], ["messageTo": "Kiran"], ["messageTo": "Madhu"], ["messageTo": "Raju"], ["messageTo": "Kiran"]]

As you can see there are 2 duplicate dictionaries in the arrOfDict.

can any one help me out in filtering the duplicates using Set or any other approach

Answer 1

Dictionaries does not conform to Hashable (or Equatable), so using Set is not an available approach in this case. For dictionaries where Key and Value types are Equatable, however, we have access to the == operator for readily performing a uniqueness filtering of the array of dictionaries:

public func ==<Key : Equatable, Value : Equatable>(
            lhs: [Key : Value], rhs: [Key : Value]) -> Bool

E.g. as follows (O(n^2))

arrOfDict = arrOfDict.enumerated()
    .filter { (idx, dict) in !arrOfDict[0..<idx].contains(where: {$0 == dict}) }
    .map { $1 }

print(arrOfDict)
// [["messageTo": "Madhu"], ["messageTo": "Kiran"], ["messageTo": "Raju"]]

// or ...
arrOfDict = arrOfDict.enumerated()
    .flatMap { (idx, dict) in !arrOfDict[0..<idx].contains(where: {$0 == dict}) ? dict : nil }

Answer 2

you can try this :

var set = NSSet(array: arrOfDict)

Answer 3

func removeDuplicates(_ arrayOfDicts: [[String: String]]) -> [[String: String]] {
var removeDuplicates = [[String: String]]()
var arrOfDict = [String]()
for dict in arrayOfDicts {
    if let name = dict["messageTo"], ! arrOfDict.contains(name) {
        removeDuplicates.append(dict)
        arrOfDict.append(name)
    }
}
return removeDuplicates
}

Answer 4

The reason why it is duplicated, because you add Dict1 and Dict2 2 times. May i ask why?

Set would not work for you, because Dictionary type does not conform to the Hashable protocol, only its key property.

You can do a validation on the dictionary, if there is already a value like that, do not append it to arrOfDict.