Remove duplicate elements from object array - ios

Question

I am attempting to remove duplicate elements of my Transaction object. The Transactions are being loaded from Firestore and displayed onto a UTableView. I tried to follow this answer [here][1] however I got an error that budgetData is not hashable. Is there a way I can remove duplicate Transactions that have the same "transId" and return an updated array of budgetdata?
var budgetData: [Transaction] = []
func loadCatTransactions(){
if let catId = self.categoryId{
guard let user = Auth.auth().currentUser?.uid else { return }
print("userFromLoadChat::\(user)")
db.collection("users").document(user).collection("Transactions")
.whereField("catId", isEqualTo: catId)
.getDocuments() {
snapshot, error in
if let error = error {
print("\(error.localizedDescription)")
} else {
self.budgetData.removeAll()
for document in snapshot!.documents {
let data = document.data()
let title = data["name"] as? String ?? ""
let date = data["date"] as? String ?? ""
let amount = data["amount"] as? Double ?? 0
let id = data["transId"] as? String ?? ""
let trans = Transaction(catId:catId,title: title, dateInfo: date, image: UIImage.groceriesIcon, amount: amount)
self.budgetData.append(trans)
DispatchQueue.main.async {
self.tableView.reloadData()
}
}
}
}
}
}
func uniq<S : Sequence, T : Hashable>(source: S) -> [T] where S.Iterator.Element == T {
var buffer = [T]()
var added = Set<T>()
for elem in source {
if !added.contains(elem) {
buffer.append(elem)
added.insert(elem)
}
}
return buffer
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.budgetData.count
}
struct Transaction {
var catId : String? = nil
var title: String
var dateInfo: String
var image: UIImage
var amount: Double
var annualPercentageRate: Double?
var trailingSubText: String?
var uid: String?
var outOfString: String?
var category: String?
var dictionary:[String:Any]{
return [
"title": title,
"dateInfo":dateInfo,
"amount":amount,
"annualPercentageRate":annualPercentageRate,
"trailingSubText":trailingSubText,
"uid": uid,
"outOfString": outOfString,
"category": category
]
}
}
[1]: Removing duplicate elements from an array in Swift

Answer 1

You need to make Transaction object Hashable. Try this
struct Transaction{
var transId: String
}
extension Transaction: Hashable{
static func ==(lhs: Transaction, rhs: Transaction) -> Bool {
return lhs.transId == rhs.transId
}
}
var budgetData = [Transaction(transId: "a"), Transaction(transId:"c"),
Transaction(transId: "a"), Transaction(transId: "d")]
var tranSet = Set<Transaction>()
budgetData = budgetData.filter { (transaction) -> Bool in
if !tranSet.contains(transaction){
tranSet.insert(transaction)
return true
}
return false
}