Swift 3 UnsafePointer($0) 不再在 Xcode 8 beta 6 中编译

Question

我的代码片段如下……：

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

…不再编译，出现以下我不明白的错误：

"'init' is unavailable: use 'withMemoryRebound(to:capacity:_)' to temporarily view memory as another layout-compatible type."

如何解决？

Answer 1

来自 Xcode 8 beta 6 的发行说明：

• 引入了Unsafe[Mutable]RawPointer 类型，替换了Unsafe[Mutable]Pointer<Void>。从UnsafePointer<T> 转换为 UnsafePointer<U> 已被禁止。 Unsafe[Mutable]RawPointer 提供了一个用于无类型内存访问的 API，以及一个用于绑定的 API 记忆到一种类型。绑定内存允许在 指针类型。见bindMemory(to:capacity:)，assumingMemoryBound(to:)， 和withMemoryRebound(to:capacity:)。 (SE-0107)

在你的情况下，你可能需要这样写：

let defaultRouteReachability = withUnsafePointer(to: &zeroAddress) {
    $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {zeroSockAddress in
        SCNetworkReachabilityCreateWithAddress(nil, zeroSockAddress)
    }
}

Answer 2

替换

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

与

guard let defaultRouteReachability = withUnsafePointer(to: &zeroAddress, {

        $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {

            SCNetworkReachabilityCreateWithAddress(nil, $0)

        }

    }) else {

        return false
    }

Answer 3

Swift 3 更新了语法，确切的解决方案是，

guard let defaultRouteReachability = withUnsafePointer(to: &zeroAddress, {
    $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
        zeroSockAddress in SCNetworkReachabilityCreateWithAddress(nil, zeroSockAddress)} 
} ) else { 
    return false 
}