Swift 2中的withUnsafePointer
Swift 2中的withUnsafePointer
提问于 2015-06-10 02:28:15
我正在尝试检查用户是否有internet连接，其中一部分过程涉及调用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($0)).takeRetainedValue()
}但是现在在Swift 2中，我收到一个错误，说
无法使用类型为“(inout sockaddr_in，(_) -> _)”的参数列表调用“withUnsafePointer”
我查看了Xcode的用法，它是：
所以我试着用
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()
}并且它们都会给出一个cannot invoke...编译时错误。在Swift 2.x中使用withUnsafePointer的正确方法是什么？
回答 3
Stack Overflow用户
回答已采纳
发布于 2015-06-10 02:34:21
错误消息具有误导性，问题在于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))
}还要注意像struct sockaddr_in这样的C结构的简化创建，它是在Swift1.2中引入的(如果我没记错的话)。
Stack Overflow用户
发布于 2016-09-20 19:04:05
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, {
_ = $0.withMemoryRebound(to: sockaddr.self, capacity: 1) { zeroSockAddress in
SCNetworkReachabilityCreateWithAddress(nil, zeroSockAddress)
}
})Stack Overflow用户
发布于 2016-11-15 18:35:27
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) {
$0.withMemoryRebound(to: sockaddr.self, capacity: 1) {zeroSockAddress in
SCNetworkReachabilityCreateWithAddress(nil, zeroSockAddress)
}
}
var flags: SCNetworkReachabilityFlags = SCNetworkReachabilityFlags(rawValue: 0)
if SCNetworkReachabilityGetFlags(defaultRouteReachability!, &flags) == false {
return false
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/30740000
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