Swift 3.0 Remove duplicates in Array of Dictionaries

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

hello did you find the solution? i am facing the same issue – Patel Jigar May 24 '17 at 07:00 — Patel Jigar, May 24 '17 at 07:00
yes jigar dfri solution worked for me. – D Madhu Kiran Raju May 25 '17 at 08:51 — D Madhu Kiran Raju, May 25 '17 at 08:51

dfrib · Accepted Answer · 2016-12-29T20:46:27.720

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 }

score 2 · Answer 2 · answered Jul 06 '17 at 04:55

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
}

score 0 · Answer 3 · answered Dec 29 '16 at 17:29

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.

score -1 · Answer 4 · answered Dec 29 '16 at 15:07

-1

you can try this :

var set = NSSet(array: arrOfDict)

answered Dec 29 '16 at 15:07

Makaille

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I don't think we need `NS` in Swift 3.0 anymore – mfaani Dec 29 '16 at 15:12

Swift 3.0 Remove duplicates in Array of Dictionaries

4 Answers4

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