objective-c - 从 Objective-C 调用 Swift 单例

Question

我在从 Objective-C 访问 Swift 单例时遇到了一些问题。

@objc class SingletonTest: NSObject {

    // swiftSharedInstance is not accessible from ObjC
    class var swiftSharedInstance: SingletonTest {
    struct Singleton {
        static let instance = SingletonTest()
        }
        return Singleton.instance
    }        
}

无法访问 swiftSharedInstance。

Answer 1

Nicky Goethlis的答案是正确的，但我只想添加另一种创建单例的方式，称为 One line Singleton" 在我最近遇到的 Swift 中，它不使用 Struct:

Singleton.swift

@objc class Singleton: NSObject {

  static let _singletonInstance = Singleton()
  private override init() {
    //This prevents others from using the default '()' initializer for this class.
  }

  // the sharedInstance class method can be reached from ObjC. (From OP's answer.)
  class func sharedInstance() -> Singleton {
    return Singleton._singletonInstance
  }

  // Some testing
  func testTheSingleton() -> String {
    return "Hello World"
  }
}

SomeObjCFile.m

Singleton *singleton = [Singleton sharedInstance];
NSString *testing = [singleton testTheSingleton];
NSLog(@"Testing---> %@",testing);