inheritance in swift

oops.swift

//: Playground - noun: a place where people can play

import UIKit

enum ServerError: Error {
    case SERVER_NOT_INITIALIZED(String)
}


class Server {
    var name: String? = nil;
    var started:Bool = false
    
    init(name:String, started: Bool) {
        self.name = name
        self.started = started
    }

    func start() {
        started = true;
    }
    
    func server(fileName: String) throws -> String? {
        if(started) {
            return "Serving using generic method: \(fileName)"
        } else {
            return nil
        }
    }
    
    func stop() {
        started = false;
    }
}

class MediaServer: Server {
    
    override init(name: String, started: Bool) {
        super.init(name:name, started:started)
    }
    
    //Can add check here if fileName ends with .mp4/.avi/.flv or .mp3/.wav
    override func server(fileName: String) throws -> String? {
        if(started) {
            return "Serving Media: \(fileName)"
        } else {
            throw ServerError.SERVER_NOT_INITIALIZED("Server not initialized")
        }
    }
}

//Generic server response
var server: Server = Server(name: "Generic Server", started: false)

//let response = server.server(fileName: "a.txt")
do {
    let response = try server.server(fileName: "a.txt")
    print("Response from \(server.name!) is \(response)")
} catch is ServerError {
    print("Exception is called: server error")
}

//Media Server response
//Generic server response
var mediaServer: Server = MediaServer(name: "Media Server", started: false)
mediaServer.start()
//let response = server.server(fileName: "a.txt")
do {
    let response = try mediaServer.server(fileName: "a.mp4")
    print("Response from \(mediaServer.name!) is \(response!)")
} catch {
    print("Exception is called: server error: \(error)")
}