Realm Primary key with OR operator - swift

Question

I am using RealmSwift for my new app. My Realm class has two primary keys.
Just an example I have a Realm Model(Product) like this:-
class Product: Object, Mappable {
dynamic var id: String? = nil
dynamic var tempId: String? = nil
dynamic var name: String? = nil
dynamic var price: Float = 0.0
dynamic var purchaseDate: Date? = nil
required convenience init?(map: Map) {
self.init()
}
//I want to do something like this
override static func primaryKey() -> String? {
return "id" or "tempId"
}
func mapping(map: Map) {
id <- map["_id"]
tempId <- map["tempId"]
name <- map["name"]
price <- map["price"]
purchaseDate <- (map["purchaseDate"], DateFormatTransform())
}
So I am creating an realm object in my device and storing into realm db with primary key tempId, as the actual primary key is the id, which is a server generated primary key is coming only after the report sync. So when I am sending multiple reports to the server with those tempId server response me back with actual id mapped with each tempId. As the report is not only created from my side so I can't keep tempId as the primary key. I thought of Compound primary key but it won't solve the problem.
So I want to create a primary key such as If id is there then that is the primary key else tempId is the primary key.
How to do this?

Answer 1

What you need essentially is a computed property as a primary key. However, this isn't supported at the moment, only stored and managed realm properties can be used as primary keys. A workaround could be to define both id and tempId to have explicit setter functions and inside the setter function you also need to set another stored property, which will be your primary key.
If you want to change id or tempId don't do it in the usual way, but do it through their setter function.
Idea taken from this GitHub issue.
class Product: Object {
dynamic var id:String? = nil
dynamic var tempId: String? = nil
func setId(id: String?) {
self.id = id
compoundKey = compoundKeyValue()
}
func setTempId(tempId: String?) {
self.tempId = tempId
compoundKey = compoundKeyValue()
}
dynamic var compoundKey: String = ""
override static func primaryKey() -> String? {
return "compoundKey"
}
func compoundKeyValue() -> String {
if let id = id {
return id
} else if let tempId = tempId {
return tempId
}
return ""
}
}

Answer 2

dynamic private var compoundKey: String = ""
required convenience init?(map: Map) {
self.init()
if let firstValue = map.JSON["firstValue"] as? String,
let secondValue = map.JSON["secondValue"] as? Int {
compoundKey = firstValue + "|someStringToDistinguish|" + "\(secondValue)"
}
}