Core Data Concurrency: Insert Or Update

concurrently_insert_update.swift

let privateContext = CoreDataStack.generatePrivateContext()

// 1. 
privateContext.perform {
    // 2. 
    for userJSON in jsonResponse {
        let id = user["id"] as! Int
        
    	// 3.
        self.searchUserBy(id: 0, in: privateContext) { (user) in
            if let user = user {
                user.update(json: userJSON)
            } else {
                let user = User(context: privateContext)
                user.update(json: userJSON)
            }
    	}

        // 4.
        do {
            try self.privateContext.save()

            self.context.performAndWait {
                do {
                    try self.context.save()
                } catch {
                    fatalError("Failure to save context: \(error)")
                }
            }
        } catch {
            fatalError("Failure to save context: \(error)")
        }
    }
}