Swift 2 中的 withUnsafePointer

Question

我正在尝试检查用户是否有互联网连接，部分过程涉及调用 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([=11=])).takeRetainedValue()
}

但是现在使用 Swift 2，我收到一条错误消息

Cannot invoke 'withUnsafePointer' with an argument list of type '(inout sockaddr_in, (_) -> _)'

我看了Xcode的用法，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()
}

而且它们都给出了 cannot invoke... 编译时错误。在Swift2.x中使用withUnsafePointer的正确方法是什么？

Answer 1

错误信息具有误导性，问题在于 SCNetworkReachabilityCreateWithAddress() 没有 return 不再是非托管对象，所以你不能调用 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([=10=]))
}

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

Answer 2

Swift 3:

var zeroAddress = sockaddr_in()
zeroAddress.sin_len = UInt8(MemoryLayout.size(ofValue: zeroAddress))
zeroAddress.sin_family = sa_family_t(AF_INET)

let defaultRouteReachability = withUnsafePointer(to: &zeroAddress, {
    _ = [=10=].withMemoryRebound(to: sockaddr.self, capacity: 1) { zeroSockAddress in
        SCNetworkReachabilityCreateWithAddress(nil, zeroSockAddress)
    }
})

Answer 3

Swift3 使用这个

         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(MemoryLayout.size(ofValue: zeroAddress))
         zeroAddress.sin_family = sa_family_t(AF_INET)

         let defaultRouteReachability = withUnsafePointer(to: &zeroAddress) {
            [=10=].withMemoryRebound(to: sockaddr.self, capacity: 1) {zeroSockAddress in
                SCNetworkReachabilityCreateWithAddress(nil, zeroSockAddress)
            }
        }

        var flags: SCNetworkReachabilityFlags = SCNetworkReachabilityFlags(rawValue: 0)
        if SCNetworkReachabilityGetFlags(defaultRouteReachability!, &flags) == false {
            return false
        }

Swift 2 中的 withUnsafePointer

withUnsafePointer in Swift 2

swift

swift2