SCNetworkReachabilitySetCallback在Swift中失敗

Question

我正在嘗試使用以下代碼為SCNetworkReachability設置回調

// Create callback
let callback:(SCNetworkReachability!, SCNetworkReachabilityFlags, UnsafeMutablePointer<Void>) -> () = { (target: SCNetworkReachability!, flags: SCNetworkReachabilityFlags, info: UnsafeMutablePointer<Void>) in
    // Do something
}

// Create UnsafeMutablePointer and initialise with callback
let p = UnsafeMutablePointer<(SCNetworkReachability!, SCNetworkReachabilityFlags, UnsafeMutablePointer<Void>) -> Void>.alloc(1)
p.initialize(callback)

// convert UnsafeMutablePointer to COpaquePointer
let cp = COpaquePointer(p) 

// convert COppaquePointer to CFunctionPointer
let fp = CFunctionPointer<(SCNetworkReachability!, SCNetworkReachabilityFlags, UnsafeMutablePointer<Void>) -> Void>(cp)

if SCNetworkReachabilitySetCallback(reachability, fp, nil) != 0 {

    println(SCError()) // SCError() is returning 0
}

SCNetworkReachabilitySetCallback調用失敗 - 有沒有其他人在這方面取得任何成功？ 知道這可能是錯的嗎？

Answer 1

從swift 1.2開始，你不能使用CFunctionPointer傳遞用swift編寫的函數。 它主要用於將已經在C中定義的函數指針傳遞給其他一些C（或objectiveC）例程。

一個可能的解決方法是在swift中使用objc_block，例如：

    let block: @objc_block (SCNetworkReachabilityRef, SCNetworkReachabilityFlags, UnsafePointer<Void>) -> Void = {
        [weak self]
        (reachability: SCNetworkReachabilityRef, flags: SCNetworkReachabilityFlags, data: UnsafePointer<Void>) in

        // Do something e.g. check if network reachability has changed

        if flags & SCNetworkReachabilityFlags(kSCNetworkReachabilityFlagsReachable) == 0 {

        }
    }

    let blockObject = imp_implementationWithBlock(unsafeBitCast(block, AnyObject.self))
    let fp = unsafeBitCast(blockObject, SCNetworkReachabilityCallBack.self)

    // e.g. you can use 169.254.0.0 for local wifi connection

    var reachability = SCNetworkReachabilityCreateWithName(kCFAllocatorDefault, ("169.254.0.0" as NSString).UTF8String).takeRetainedValue()
    var context = SCNetworkReachabilityContext()

    if SCNetworkReachabilitySetCallback(reachability!, fp, &context) == 1 {
        if SCNetworkReachabilityScheduleWithRunLoop(reachability!, CFRunLoopGetCurrent(), NSDefaultRunLoopMode) == 0 {
            println(SCError())
        }
    }

Answer 2

SCNetworkReachabilitySetCallback函數返回一個布爾值。

https://developer.apple.com/LIBRARY/ios/documentation/SystemConfiguration/Reference/SCNetworkReachabilityRef/index.html#//apple_ref/c/func/SCNetworkReachabilitySetCallback

TRUE值通常定義為1。

從而

if SCNetworkReachabilitySetCallback(reachability, fp, nil) != 0 {

    println(SCError()) // SCError() is returning 0
}

可能只會打印0。