Question

我正在尝试在基于Swift的新应用程序中使用Tony Million的Reachability。我在Obj C中编写的另一个应用程序中实现了它，但是我遇到了在Swift中获取正确语法的问题。代码块如下：

override func viewDidLoad() {
    super.viewDidLoad()
    messageText.text = ""

    var reach: Reachability = Reachability(hostName: "www.apple.com")

    NSNotificationCenter.defaultCenter().addObserver(self, selector: "reachabilityChanged", name: kReachabilityChangedNotification, object: nil)


    reach.reachableBlock = Reachability()
    {
        dispatch_async(dispatch_get_main_queue(), {
            self.messageText.text = "Enter search criteria...";
            })
    }

    reach.unreachableBlock = Reachability()
    {
        dispatch_async(dispatch_get_main_queue(), {
            self.messageText.text = "Attempting to contact network...";
            })
    }

    reach.startNotifier()

}

AND

func reachabilityChanged(note: NSNotification)
{

    var reach: Reachability = Reachability()
    if(reach.isReachable())
    {
        messageText.text = "Enter search criteria...";
    }
    else
    {
        messageText.text = "Attempting to contact network...";
    }

}

我的问题是第一，我的“可达”和“无法访问”的“块”不是正确的语法，我对这些块的正确语法是什么感到茫然。我的第二个问题是“reachabilityChanged”功能。我收到一个错误，指出“ - [_ TtC9icdDRPlus20SearchViewController reachabilityChanged]：无法识别的选择器发送到实例”我再次感到茫然。考虑我的Obj C代码如下：

-(void)viewDidLoad
{
[super viewDidLoad];
NSString *popUpShownOnce = @"YES";
NSInteger swipeCount = 0;
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:popUpShownOnce forKey:@"popDisplayed"];
[defaults setInteger:swipeCount forKey:@"showswipearrows"];

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(reachabilityChanged:)
                                             name:kReachabilityChangedNotification
                                           object:nil];
[[UIApplication sharedApplication] setStatusBarHidden:NO];

Reachability * reach = [Reachability reachabilityWithHostname:@"somesite.com"];

reach.reachableBlock = ^(Reachability * reachability)
{
    dispatch_async(dispatch_get_main_queue(), ^{
        searchForText.placeholder = @"Enter search criteria...";
    });
};

reach.unreachableBlock = ^(Reachability * reachability)
{
    dispatch_async(dispatch_get_main_queue(), ^{
        searchForText.placeholder = @"Attempting to contact network...";
    });
};

[reach startNotifier];
}

-(void)reachabilityChanged:(NSNotification*)note
{
Reachability * reach = [note object];

if([reach isReachable])
{
    searchForText.placeholder = @"Enter search criteria...";
}
else
{
    searchForText.placeholder = @"Attempting to contact network...";
}
}

非常感谢协助。问题如下： 1.从Obj C到Swift的可到达和无法到达的块的正确翻译是什么？ 2.如果我的addObserver调用正确，为什么我会收到无法识别的选择器错误？如果不正确，那么正确的呼叫是什么？

提前致谢。

Answer 1

闭包的正确语法是{ (<params>) -> <return type> in <statements> }：

reach.reachableBlock = { (reachability) in
    dispatch_async(dispatch_get_main_queue(), {
        self.messageText.text = "Enter search criteria...";
        })
}

使用NSNotificationCenter，看起来你错过了选择器参数中的冒号：

NSNotificationCenter.defaultCenter().addObserver(self, selector: "reachabilityChanged:", name: kReachabilityChangedNotification, object: nil)

Answer 2

在进行@Austin推荐的更改后，您的错误是SCNetworkReachabilitySetCallback中的self.reachabilityRef为NULL。

尝试：

func reachabilityChanged(note: NSNotification!) {

    var reach: Reachability! = Reachability(reachabilityRef: note.object as SCNetworkReachability)

    if(reach.isReachable()) {
        messageText.text = "Enter search criteria...";
    } else {
        messageText.text = "Attempting to contact network...";
    }
}

更新：

似乎SCNetworkReachability目前还没有完全使用Swift：根据这个：https://twitter.com/marksands/status/474717606004273152

Answer 3

我让它像这样工作：

var reachability: Reachability?

override func viewDidLoad() {
    super.viewDidLoad()

    // Setup reachability
    reachability = Reachability(hostName: "www.google.com")
    reachability!.reachableBlock = { (reach) in
        dispatch_async(dispatch_get_main_queue(), {
            self.titleLabel.attributedText = Utilities.myAttributedText("Online", mySize: 18, myFont: "HelveticaNeue", myColor: UIColor.whiteColor())
            self.titleLabel.sizeToFit()
            })
    }
    reachability!.unreachableBlock = { (reach) in
        dispatch_async(dispatch_get_main_queue(), {
            self.titleLabel.attributedText = Utilities.myAttributedText("Offline", mySize: 18, myFont: "HelveticaNeue", myColor: UIColor.whiteColor())
            self.titleLabel.sizeToFit()
            })
    }
    reachability!.startNotifier()
}

Answer 4

这对我有用：

 //Reachability
    myReachabilityInstance = Reachability(hostName: "www.google.com")
    myReachabilityInstance?.reachableOnWWAN = false
    NSNotificationCenter.defaultCenter().addObserver(self, selector: "reachabilityDidChangeMethod", name: kReachabilityChangedNotification, object: nil)
    myReachabilityInstance?.startNotifier()

这些代码块出了什么问题？

4 个答案: