Swift 2中的withUnsafePointer [英] withUnsafePointer in Swift 2

问题描述

我正在尝试检查用户是否具有Internet连接，并且该过程的一部分涉及调用withUnsafePointer.在Swift 1.x中，我可以使用:

I'm trying to check if the user has internet connection, and part of the process involves invoking withUnsafePointer. In Swift 1.x, I was able to use:

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()
}

但是现在有了Swift 2，我说错了

But now with Swift 2, I'm getting an error saying

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

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

我查看了Xcode的用法，即:

I looked Xcode's usage, which is:

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Swift 2.x中使用withUnsafePointer的正确方法是什么?

And they both give a cannot invoke... compile-time error. What is the correct way to use withUnsafePointer in Swift 2.x?

推荐答案

错误消息具有误导性，问题在于 SCNetworkReachabilityCreateWithAddress()不返回 非托管对象了，所以您不能调用 takeRetainedValue():

The error message is misleading, the problem is that SCNetworkReachabilityCreateWithAddress() does not return an unmanaged object anymore, so you must not call 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))
}

还要注意简化的C结构的创建，例如struct sockaddr_in Swift 1.2引入(如果我没记错的话).

Note also the simplified creation of C structs like struct sockaddr_in which was introduced with Swift 1.2 (if I remember correctly).

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