/// Creates a new instance by decoding from the given decoder.
public init(from decoder: Decoder) throws

onload

oncomplete

required convenience init(from decoder: Decoder) throws {
        // since we are decoding json to managedobject, so using background managedobject context
        guard let backgrounManagedObjectContext = CodingUserInfoKey.backgrounManagedObjectContext,
            let parentLoginKey = CodingUserInfoKey.parentLogin,
            let userTypeKey = CodingUserInfoKey.userType,
            let managedObjectContext = decoder.userInfo[backgrounManagedObjectContext] as? NSManagedObjectContext,
            let parentLogin:String = decoder.userInfo[parentLoginKey] as? String,
            let userType:Int64 = decoder.userInfo[userTypeKey] as? Int64,
        let entity = NSEntityDescription.entity(forEntityName: "User", in: managedObjectContext) else {
                fatalError("Failed to decode User")
        }
        let container = try decoder.container(keyedBy: CodingKeys.self)
        
        var existingUser:User?
        do {
            let fetchRequest:NSFetchRequest = User.fetchRequest()
            let predicate = NSPredicate(format: "login CONTAINS[cd] %@ and parentLogin CONTAINS[cd] %@ and userType == %d", try container.decodeIfPresent(String.self, forKey: .login) ?? "", parentLogin, userType)
            fetchRequest.predicate = predicate
            
            let fetchResults = try managedObjectContext.fetch(fetchRequest)
            
            if (fetchResults.count > 0){
                existingUser = fetchResults.first
            }
            
        } catch let error {
            print(error)
        }
        // This is possible
        self.init(entity: entity, insertInto: managedObjectContext)
       // But we cannot do, self is immutable
       self = existingUser
}

if existingUser != nil {
            self.avatarURL = existingUser?.avatarURL
            self.bio = existingUser?.bio
            self.blog = existingUser?.blog
            self.company = existingUser?.company
            self.createdAt = existingUser?.createdAt
            self.email = existingUser?.email
            self.followers = existingUser?.followers ?? 0
            self.followersURL = existingUser?.followersURL
            self.following = existingUser?.following ?? 0
            self.followingURL = existingUser?.followingURL
            self.location = existingUser?.location
            self.login = existingUser?.login
            self.name = existingUser?.name
            self.publicGists = existingUser?.publicGists ?? 0
            self.publicRepos = existingUser?.publicRepos ?? 0
            self.gistsURL = existingUser?.gistsURL
            self.updatedAt = existingUser?.updatedAt
            self.url = existingUser?.url
            self.parentLogin = existingUser?.parentLogin
            self.userType = existingUser?.userType ?? 1
            
            managedObjectContext.delete(existingUser!)
        }
        
        self.avatarURL = try container.decodeIfPresent(String.self, forKey: .avatarURL)
        self.bio = try container.decodeIfPresent(String.self, forKey: .bio)
        self.blog = try container.decodeIfPresent(String.self, forKey: .blog)
        self.company = try container.decodeIfPresent(String.self, forKey: .company)
        self.createdAt = try container.decodeIfPresent(Date.self, forKey: .createdAt)
        self.email = try container.decodeIfPresent(String.self, forKey: .email)
        self.followers = try container.decodeIfPresent(Int64.self, forKey: .followers) ?? 0
        self.followersURL = try container.decodeIfPresent(String.self, forKey: .followersURL)
        self.following = try container.decodeIfPresent(Int64.self, forKey: .following) ?? 0
        self.followingURL = try container.decodeIfPresent(String.self, forKey: .followingURL)
        self.location = try container.decodeIfPresent(String.self, forKey: .location)
        self.login = try container.decodeIfPresent(String.self, forKey: .login)
        self.name = try container.decodeIfPresent(String.self, forKey: .name)
        self.publicGists = try container.decodeIfPresent(Int64.self, forKey: .publicGists) ?? 0
        self.publicRepos = try container.decodeIfPresent(Int64.self, forKey: .publicRepos) ?? 0
        self.gistsURL = try container.decodeIfPresent(String.self, forKey: .gistsURL)
        self.updatedAt = try container.decodeIfPresent(Date.self, forKey: .updatedAt)
        self.url = try container.decodeIfPresent(String.self, forKey: .url)
        self.parentLogin = parentLogin
        self.userType = userType