withSnsafePointer in Swift 2

Question

我正在尝试检查用户是否具有互联网连接,并且该过程的一部分涉及调用withUnsafePointer.在Swift 1.x中,我能够使用:

var zeroAddress = sockaddr_in(sin_len: 0, sin_family: 0, sin_port: 0, sin_addr: in_addr(s_addr: 0), sin_zero: (0, 0, 0, 0, 0, 0, 0, 0))
zeroAddress.sin_len = UInt8(sizeofValue(zeroAddress))
zeroAddress.sin_family = sa_family_t(AF_INET)

let defaultRouteReachability = withUnsafePointer(&zeroAddress){
    SCNetworkReachabilityCreateWithAddress(nil, UnsafePointer($0)).takeRetainedValue()
}

但是现在使用Swift 2,我收到一个错误说法

无法使用类型为'(inout sockaddr_in,(_) - > _)'的参数列表调用'withUnsafePointer'

我看了Xcode的用法,它是:

所以我尝试使用

withUnsafePointer(&zeroAddress) {(pointer: UnsafePointer<sockaddr_in>) -> sockaddr_in in
    SCNetworkReachabilityCreateWithAddress(nil, pointer).takeRetainedValue()
}

以及

withUnsafePointer(&zeroAddress) {(pointer: UnsafePointer<sockaddr_in>) -> AnyObject in
    SCNetworkReachabilityCreateWithAddress(nil, pointer).takeRetainedValue()
}

它们都会产生cannot invoke...编译时错误.withUnsafePointer在Swift 2.x中使用的正确方法是什么？

Answer 1

错误消息具有误导性,问题是 SCNetworkReachabilityCreateWithAddress()不再返回非托管对象,因此您不能调用 takeRetainedValue():

var zeroAddress = sockaddr_in()
zeroAddress.sin_len = UInt8(sizeofValue(zeroAddress))
zeroAddress.sin_family = sa_family_t(AF_INET)

let defaultRouteReachability = withUnsafePointer(&zeroAddress) {
    SCNetworkReachabilityCreateWithAddress(nil, UnsafePointer($0))
}

另请注意struct sockaddr_in,在Swift 1.2中引入的C结构的简化创建(如果我没记错的话).