Removing Duplicates From Array of Custom Objects Swift

Question

I have a custom class defined as follows :

class DisplayMessage : NSObject {
var id : String?
var partner_image : UIImage?
var partner_name : String?
var last_message : String?
var date : NSDate?
}

Now I have an array myChats = [DisplayMessage]?. The id field is unique for each DisplayMessage object. I need to check my array and remove all duplicates from it, essentially ensure that all objects in the array have a unique id. I have seen some solutions using NSMutableArray and Equatable however I'm not sure how to adapt them here; I also know of Array(Set(myChats)) however that doesn't seem to work for an array of custom objects.

Answer 1

Here is an Array extension to return the unique list of objects based on a given key:

extension Array {
    func unique<T:Hashable>(map: ((Element) -> (T)))  -> [Element] {
        var set = Set<T>() //the unique list kept in a Set for fast retrieval
        var arrayOrdered = [Element]() //keeping the unique list of elements but ordered
        for value in self {
            if !set.contains(map(value)) {
                set.insert(map(value))
                arrayOrdered.append(value)
            }
        }

        return arrayOrdered
    }
}

for your example do:

let uniqueMessages = messages.unique{$0.id ?? ""}