我正在尝试在互联网连接恢复且updateOnConnection变量为true 时调用一个函数。这是我的代码:
updateOnConnection
func checkForConnection() { let host = "reddit.com" var context = SCNetworkReachabilityContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil) let reachability = SCNetworkReachabilityCreateWithName(nil, host)! SCNetworkReachabilitySetCallback(reachability, { (_, flags, _) in if flags.rawValue == 0 { //internet is not connected } else { //internet became connected if self.updateOnConnection { self.refreshWallpaper() } } }, &context) SCNetworkReachabilityScheduleWithRunLoop(reachability, CFRunLoopGetMain(), kCFRunLoopCommonModes) }
我的问题是这些行:
if self.updateOnConnection { self.refreshWallpaper() }
导致错误:“ A C function pointer cannot be formed from a closure that captures context”
A C function pointer cannot be formed from a closure that captures context
我不确定如何检查状态updateOnConnection并调用refreshWallpaper()监视Internet连接变化的闭包。如何解决此问题,或者我应该使用完全不同的解决方法?
refreshWallpaper()
类似于如何将实例方法用作仅使用func或立即数闭包的函数的回调中一样,您必须转换 self为void指针,将其存储在上下文中,然后将其转换回闭包中的对象指针:
self
func checkForConnection() { let host = "reddit.com" var context = SCNetworkReachabilityContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil) context.info = UnsafeMutablePointer(Unmanaged.passUnretained(self).toOpaque()) let reachability = SCNetworkReachabilityCreateWithName(nil, host)! SCNetworkReachabilitySetCallback(reachability, { (_, flags, info) in if flags.rawValue == 0 { //internet is not connected } else { //internet became connected let mySelf = Unmanaged<ViewController>.fromOpaque(COpaquePointer(info)).takeUnretainedValue() if mySelf.updateOnConnection { mySelf.refreshWallpaper() } } }, &context) SCNetworkReachabilityScheduleWithRunLoop(reachability, CFRunLoopGetMain(), kCFRunLoopCommonModes) }
备注: if flags.rawValue == 0可以表示得稍微优雅一些if flags.isEmpty,但是您 实际上 应该检查的是if flags.contains(.Reachable)。
if flags.rawValue == 0
if flags.isEmpty
if flags.contains(.Reachable)
Swift 3的更新(Xcode 8 beta 6):
func checkForConnection() { let host = "reddit.com" var context = SCNetworkReachabilityContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil) context.info = UnsafeMutableRawPointer(Unmanaged.passUnretained(self).toOpaque()) let reachability = SCNetworkReachabilityCreateWithName(nil, host)! SCNetworkReachabilitySetCallback(reachability, { (_, flags, info) in if let info = info { if flags.rawValue == 0 { //internet is not connected } else { //internet became connected let mySelf = Unmanaged<ViewController>.fromOpaque(info).takeUnretainedValue() // ... } } }, &context) SCNetworkReachabilityScheduleWithRunLoop(reachability, CFRunLoopGetMain(), CFRunLoopMode.commonModes.rawValue) }