xcode - 在应用程序启动 OSX 时运行代码

Question

我正在寻找一种方法，让应用程序启动后就不断运行某些代码。我正在尝试使用 swiftSockets 制作一个简单的点对点聊天应用程序。

import Cocoa
import CryptoSwift

class MasterViewController: NSViewController {

    @IBOutlet var msgField: NSTextField!
    @IBOutlet var msgWindow: NSTextView!

    let server:UDPServer = UDPServer(addr: "127.0.0.1", port: 5000)

    override func viewDidLoad() {
        super.viewDidLoad()

    }

    func receive() {
        let data = server.recv(1024)
        let string = NSData.withBytes(data.0!)
        let str = NSString(data: string, encoding: NSUTF8StringEncoding) as String?
        msgWindow.string! += server.addr + " says: " + str! + "\n"
    }

    @IBAction func send(sender: NSButton) {
        msgWindow.string! += "I said: " + msgField.stringValue + "\n"
        msgField.stringValue = ""
        server.send(str: msgField.stringValue)
        let data = server.recv(1024)
        let string = NSData.withBytes(data.0!)
        let str = NSString(data: string, encoding: NSUTF8StringEncoding) as String?
        msgWindow.string! += server.addr + " says: " + str! + "\n"
    }
}

我有上面的代码，发送效果很好，但是，如何让接收函数在应用程序运行后立即在后台运行？

Answer 1

只需在 viewDidLoad() 或 viewDidAppear() 函数中调用接收函数即可。要在后台运行它，请考虑dispatch_async()或dispatch_sync()

let priority = DISPATCH_QUEUE_PRIORITY_DEFAULT
dispatch_async(dispatch_get_global_queue(priority, 0)) {
    // do some tasks, in this case call receive()
    dispatch_async(dispatch_get_main_queue()) {
        // update some UI
    }
}

如果您只是想定期运行它而不需要将其传输到后台，请考虑使用 NSTimer，并调用其 ScheduledTimerWithTimeInterval 函数，如下所示:

let timer = NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: "receive", userInfo: nil, repeats: true)

第一个参数是以秒为单位的时间间隔，选择要定期调用的函数(在本例中为接收)。