Singleton in Swift 4

SingletonInSwift4.swift

// 1. --- The simple version...
class SingletonManager {
    static let sharedInstance = SomeManager()
}
// The singleton object will then be accessible through the SingletonManager.sharedInstance() class method.


// 2. --- Or the more complex and secure version...
// [Full credit to](https://cocoacasts.com/what-is-a-singleton-and-how-to-create-one-in-swift/)
class NetworkManager {

    // MARK: - Properties

    private static var sharedNetworkManager: NetworkManager = {
        let networkManager = NetworkManager(baseURL: API.baseURL)

        // Configuration
        // ...

        return networkManager
    }()

    // MARK: -

    let baseURL: URL

    // Initialization

    private init(baseURL: URL) {
        self.baseURL = baseURL
    }

    // MARK: - Accessors

    class func shared() -> NetworkManager {
        return sharedNetworkManager
    }

}