Remove duplicate elements in swift array of objects - ios

Question

So I have a section in my app which displays events that your followers are going to. I successfully pull the followers and there corresponding events. I then add those events to a bigger array of event objects. I am currently having trouble removing the duplicates I have tried many extensions but it doesn't seem to be working. I figure it is because the array contains different objects with different memory addresses so when I compare them they aren't the same regardless of the fact that the content is. I have been messing with this for a while now and can't really figure anything out. if anyone could help me I would appreciate it.
This is the method grabs the events and returns them to an array in my main VC.
static func showFollowingEvent(for followerKey: String,completion: #escaping (Event) -> Void) {
//getting firebase root directory
let ref = Database.database().reference()
ref.child("users").child(followerKey).child("Attending").observeSingleEvent(of: .value, with: { (attendingSnapshot) in
print(attendingSnapshot)
guard var eventKeys = attendingSnapshot.children.allObjects as? [DataSnapshot] else{return}
for event in eventKeys{
let dispatchGroup = DispatchGroup()
dispatchGroup.enter()
EventService.show(forEventKey: event.key, completion: { (event) in
dispatchGroup.leave()
completion(event!)
})
}
}) { (err) in
print("couldn't grab event info",err)
}
} print("couldn't grab event info",err)
}
}
This is the function that receives the events and reloads the collectionView upon getting them.
#objc func grabFriendsEvents(){
print("Attempting to see where your friends are going")
UserService.following { (user) in
for following in user {
print(following.username as Any)
PostService.showFollowingEvent(for: following.uid, completion: { (event) in
self.friendsEvents.append(event)
// self.friendsEvents.append(contentsOf: event)
// leave here
self.allEvents2["Friends Events"] = self.friendsEvents.removeDuplicates()
self.collectionView?.reloadData()
})
}
}
}
I tried these extensions which I saw in previous questions and nothing worked.
extension Array where Element: Equatable {
func removeDuplicates() -> [Element] {
var result = [Element]()
for value in self {
if result.contains(value) == false {
result.append(value)
}
}
return result
}
mutating func removeDuplicatesTwo() {
var result = [Element]()
for value in self {
if !result.contains(value) {
result.append(value)
}
}
self = result
}
}
import Foundation
import FirebaseDatabase.FIRDataSnapshot
#objc(Event)
class Event:NSObject{
var key: String?
let currentEventName: String
let currentEventImage: String
let currentEventPromo: String?
let currentEventDescription: String
//nested properties
let currentEventStreetAddress: String
let currentEventCity: String
let currentEventState: String
let currentEventDate: String?
let currentEventEndDate: String?
let currentEventTime: String?
let currentEventEndTime: String?
let currentEventZip: Int
var category: String
//nested properties stop
var currentAttendCount: Int
var isAttending = false
var eventDictionary: [String: Any]{
let dateDict = ["start:date":currentEventDate, "start:time": currentEventTime,"end:time":currentEventEndTime, "end:date": currentEventEndDate]
return ["event:name":currentEventName,"event:imageURL" : currentEventImage,
"event:description": currentEventDescription, "attend:count": currentAttendCount,
"event:street:address": currentEventStreetAddress,"event:zip": currentEventZip,
"event:state": currentEventState, "event:city": currentEventCity, "event:promo": currentEventPromo ?? "", "event:date": dateDict, "event:category":category]
}
init(currentEventKey: String, dictionary: [String:Any]) {
self.key = currentEventKey
self.currentEventName = dictionary["event:name"] as? String ?? ""
self.currentEventImage = dictionary["event:imageURL"] as? String ?? ""
self.currentEventDescription = dictionary["event:description"] as? String ?? ""
self.currentEventPromo = dictionary["event:promo"] as? String ?? ""
self.currentAttendCount = dictionary["attend:count"] as? Int ?? 0
self.category = dictionary["event:category"] as? String ?? ""
//nested properties
self.currentEventStreetAddress = dictionary["event:street:address"] as? String ?? ""
self.currentEventCity = dictionary["event:city"] as? String ?? ""
self.currentEventState = dictionary["event:state"] as? String ?? ""
self.currentEventZip = dictionary["event:zip"] as? Int ?? 0
let eventDate = dictionary["event:date"] as? [String: Any]
self.currentEventDate = eventDate?["start:date"] as? String ?? ""
self.currentEventTime = eventDate?["start:time"] as? String ?? ""
self.currentEventEndTime = eventDate?["end:time"] as? String ?? ""
self.currentEventEndDate = eventDate?["end:date"] as? String ?? ""
}
init?(snapshot: DataSnapshot) {
guard let dict = snapshot.value as? [String : Any],
let currentEventName = dict["event:name"] as? String,
let currentEventImage = dict["event:imageURL"] as? String,
let currentEventDescription = dict["event:description"] as? String,
let currentEventPromo = dict["event:promo"] as? String,
let category = dict["event:category"] as? String,
let currentEventStreetAddress = dict["event:street:address"] as? String,
let currentEventCity = dict["event:city"] as? String,
let currentEventState = dict["event:state"] as? String,
let currentEventZip = dict["event:zip"] as? Int,
let currentAttendCount = dict["attend:count"] as? Int,
let eventDate = dict["event:date"] as? [String: Any],
let currentEventDate = eventDate["start:date"] as? String,
let currentEventEndDate = eventDate["end:date"] as? String,
let currentEventTime = eventDate["start:time"] as? String,
let currentEventEndTime = eventDate["end:time"] as? String
else { return nil }
self.key = snapshot.key
self.currentEventName = currentEventName
self.currentEventImage = currentEventImage
self.currentEventDescription = currentEventDescription
self.currentEventStreetAddress = currentEventStreetAddress
self.currentEventCity = currentEventCity
self.currentEventState = currentEventState
self.currentEventZip = currentEventZip
self.currentAttendCount = currentAttendCount
self.currentEventPromo = currentEventPromo
self.currentEventDate = currentEventDate
self.currentEventTime = currentEventTime
self.currentEventEndTime = currentEventEndTime
self.category = category
self.currentEventEndDate = currentEventEndDate
}
static func ==(lhs: Event, rhs: Event) -> Bool {
return lhs.key == rhs.key
}
}

Answer 1

Classes of type NSObject will automatically call isEqual() for the contains() method. You can override the superclass's implementation to fit your logic.
If your class HAS to inherit NSObject, then use:
class Event: NSObject {
var key: String?
init(key: String) {
self.key = key
}
override func isEqual(_ object: Any?) -> Bool {
guard let event = object as? Event else { return false }
return self.key == event.key
}
}
var event = Event(key: "abc")
var eventCopy = Event(key: "abc")
extension Array where Element:Equatable {
func removeDuplicates() -> [Element] {
return reduce(into: []) { result, element in
if !result.contains(element) {
result.append(element)
}
}
}
}
var events = [event, eventCopy]
events = events.removeDuplicates()
print(events.count)
If your class does not inherit NSObject, make it conform to the Equatable protocol.
class Event: Equatable {
var key: String?
init(key: String) {
self.key = key
}
static func ==(lhs: Event, rhs: Event) -> Bool {
return lhs.key == rhs.key
}
}
var event = Event(key: "abc")
var eventCopy = Event(key: "abc")
extension Array where Element:Equatable {
func removeDuplicates() -> [Element] {
var result = [Element]()
for value in self {
if result.contains(value) == false {
result.append(value)
}
}
return result
}
}
var events = [event, eventCopy]
events = events.removeDuplicates()
print(events.count)

Answer 2

You have to make Event class conform to Equatable protocol