关闭捕获上下文Swift

概述当我尝试更改闭包中的变量时,我收到此错误： A C function pointer cannot be formed from a closure that captures context 是否有解决方法或是否仍然可以更改闭包内的变量？ 我的代码： let callback: @convention(c) (readStream: CFWriteStream!, event: CFStream 当我尝试更改闭包中的变量时,我收到此错误：

A C function pointer cannot be formed from a closure that captures context

是否有解决方法或是否仍然可以更改闭包内的变量？

我的代码：

let callback: @convention(c) (readStream: CFWriteStream!,event: CFStreamEventType,data: UnsafeMutablePointer<VoID>) -> VoID = {    (readStream,event,data) -> VoID in    switch event {    case CFStreamEventType.ErrorOccurred:        self.isError = true        break    case CFStreamEventType.EndEncountered:        self.isRunLoop = false        break    case CFStreamEventType.HasBytesAvailable:        break    case CFStreamEventType.OpenCompleted:        break    case CFStreamEventType.CanAcceptBytes:        self.bytesWritten = CFWriteStreamWrite(readStream,self.buffer,self.leftOverSize)        break    default:        break    }}let registeredEvents: CFOptionFlags =    CFStreamEventType.CanAcceptBytes.rawValue |    CFStreamEventType.HasBytesAvailable.rawValue |    CFStreamEventType.ErrorOccurred.rawValue |    CFStreamEventType.EndEncountered.rawValue |    CFStreamEventType.None.rawValuevar context = CFStreamClIEntContext(version: CFIndex(0),info: nil,retain: nil,release: nil,copyDescription: nil)let stream = CFWriteStreamCreateWithFTPURL(nil,uploadURL).takeUnretainedValue()CFWriteStreamSetClIEnt(stream,registeredEvents,callback,&context)

解决方法 我假设你想使用这个回调将它作为第三个参数(clIEntCB)传递给 CFWriteStreamSetClient.

由于该参数具有以下类型定义

typedef voID (*CFWriteStreamClIEntCallBack) ( CFWriteStreamRef stream,CFStreamEventType eventType,voID *clIEntCallBackInfo );

您只能使用全局函数或不从周围上下文捕获任何变量(如self)的闭包.

在这种情况下你可以做的是将self传递给CFStreamClIEntContext结构的info字段(CFWriteStreamSetClIEnt的第4个参数),并使用该信息在闭包内重构self：

let callback: @convention(c) (readStream: CFWriteStream!,data) -> VoID in    // assuming your class name is ClIEnt    let clIEnt = unsafeBitCast(data.memory,ClIEnt.self)    switch event {    case CFStreamEventType.ErrorOccurred:        clIEnt.isError = true    case CFStreamEventType.EndEncountered:        clIEnt.isRunLoop = false    case CFStreamEventType.HasBytesAvailable:        break    case CFStreamEventType.OpenCompleted:        break    case CFStreamEventType.CanAcceptBytes:        clIEnt.bytesWritten = CFWriteStreamWrite(readStream,clIEnt.buffer,clIEnt.leftOverSize)    default:        break    }}var context = CFStreamClIEntContext(version: 0,info: unsafeBitCast(self,UnsafeMutablePointer<VoID>.self),copyDescription: nil)CFWriteStreamSetClIEnt(stream,&context)

注意.与Objective-C一样,您需要确保在流之前不会销毁self,否则如果流接收到新事件,您可能会遇到崩溃.

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