Swift - 委托（delegate）5秒看懂

//定義一個協議
protocol LogManagerDelegate {
    func writeLog()
}
 
//用戶登錄類
class UserController {
    var delegate : LogManagerDelegate?
     
    func login() {
        //查看是否有委托，然后調用它
        delegate?.writeLog()
    }
}
 
//日志管理類
class SqliteLogManager : LogManagerDelegate {
    func writeLog() {
        print("將日志記錄到sqlite數據庫中")
    }
}
 
 
//使用
let userController = UserController()
userController.login()  //不做任何事
 
let sqliteLogManager = SqliteLogManager()
userController.delegate = sqliteLogManager
userController.login()  //輸出“將日志記錄到sqlite數據庫中”