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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