A method instance defining a singleton in Swift

What is a singleton

The singleton is one of the simplest design patterns, and even some pattern gurus don't call it a pattern, but an implementation technique, because design patterns focus on the abstraction of relationships between objects, while singletons have only one object of their own.

Singleton pattern (Singleton Pattern), also known as singleton pattern, is a common software design pattern. When this pattern is applied, the class of the singleton must ensure that only 1 instance exists.

The single-instance Singleton design pattern is probably the most widely discussed and used design pattern, and probably the most frequently asked design pattern in an interview. The main purpose of this design pattern is that only one instance of a class can occur in the entire system. There are certain things you can do, such as global configuration information for your software, or an Factory, or a master class, etc.

How do I create singletons in swift

There are two ways to create singletons in swift

Global variables

let sharedNetworkManager = NetworkManager(baseURL: API.baseURL)
class NetworkManager {
 // MARK: - Properties
 let baseURL: URL
 // Initialization
 init(baseURL: URL) {
 self.baseURL = baseURL
 }
}

This global variable is used for reference

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
 print(sharedNetworkManager)
 return true
}

Static properties and ways to privatize methods

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
 }
}

Class methods are called directly for reference

NetworkManager.shared()

conclusion

What Is a Singleton and How To Create One In Swift