Swift 闭包捕获上下文

当我尝试更改闭包中的变量时，会出现以下错误：

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

let callback: @convention(c) (readStream: CFWriteStream!, event: CFStreamEventType, data: UnsafeMutablePointer<Void>) -> Void = {
    (readStream, event, 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), retain: nil, release: nil, copyDescription: nil)
CFWriteStreamSetClient(stream, 0, callback, &context)

是否有解决方法，或者是否仍然可以更改闭包中的变量

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.rawValue

var context = CFStreamClientContext(version: CFIndex(0), info: nil, retain: nil, release: nil, copyDescription: nil)
let stream = CFWriteStreamCreateWithFTPURL(nil, uploadURL).takeUnretainedValue()

CFWriteStreamSetClient(stream, registeredEvents, callback, &context)

let回调：@convention（c）（readStream:CFWriteStream！，事件：cfstreamventtype，数据：UnsafeMutablePointer）->Void={
（读取流、事件、数据）->Void in
切换事件{
案例cfstreamventtype.error发生：
self.isError=true
打破
案例CfStreamVentType.EndEnCounted：
self.isrunlop=false
打破
案例cfstreamventtype.hasbytes可用：
打破
案例cfstreamventtype.OpenCompleted：
打破
案例CFStreamVentType.CanAcceptBytes：
self.bytesWrite=CFWriteStreamWrite（读流、self.buffer、self.leftOverSize）
打破
违约：
打破
}
}
let registeredEvents:CFOptionFlags=
CFStreamEventType.CanAcceptBytes.rawValue|
cfstreamventtype.HasBytesAvailable.rawValue|
CFStreamEventType.ErrorOccurrend.rawValue|
cfstreamventtype.endencounted.rawValue|
cfstreamventtype.None.rawValue
var context=CFStreamClientContext（版本：CFIndex（0），信息：nil，保留：nil，发布：nil，副本描述：nil）
let stream=CFWriteStreamCreateWithFTPURL（nil，uploadURL）。takeUnrepainedValue（）
CFWriteStreamSetClient（流、registeredEvents、回调和上下文）

我假设您希望使用此回调将其作为第三个参数（

clientCB

）传递给

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，您可以将

self

传递到

CFStreamClientContext

结构的

info

字段（CFWriteStreamSetClient的第四个参数），并使用该信息在闭包中重建

self

：

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

let callback: @convention(c) (readStream: CFWriteStream!, event: CFStreamEventType, data: UnsafeMutablePointer<Void>) -> Void = {
    (readStream, event, 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), retain: nil, release: nil, copyDescription: nil)
CFWriteStreamSetClient(stream, 0, callback, &context)

let回调：@convention（c）（readStream:CFWriteStream！，事件：cfstreamventtype，数据：UnsafeMutablePointer）->Void={
（读取流、事件、数据）->Void in
//假设您的类名是Client
let client=unsafeBitCast（data.memory，client.self）
切换事件{
案例cfstreamventtype.error发生：
client.isError=true
案例CfStreamVentType.EndEnCounted：
client.isrunlop=false
案例cfstreamventtype.hasbytes可用：
打破
案例cfstreamventtype.OpenCompleted：
打破
案例CFStreamVentType.CanAcceptBytes：
client.bytesWrite=CFWriteStreamWrite（readStream、client.buffer、client.leftOverSize）
违约：
打破
}
}
var context=CFStreamClientContext（版本：0，信息：unsafeBitCast（self，UnsafeMutablePointer.self），retain:nil，release:nil，copyDescription:nil）
CFWriteStreamSetClient（流、0、回调和上下文）

---

注意。与Objective-C一样，您需要确保

self

在流被销毁之前没有被销毁，否则如果流接收到新事件，您可能会崩溃。

回调必须是一个全局函数或一个不捕获上下文的闭包。类似的问题：或者。我如何知道是否有错误？您必须将

self

转换为空指针，将其作为用户数据传递给回调，然后在回调中将其转换回对象指针。另请参见。我一直收到以下错误：

命令失败，原因是信号：分段错误：11

。在哪一行？如何调用

CFWriteStreamSetClient

？@HovyTech这似乎是一个swift编译器问题，请参阅。但是，您将

nil

传递给了

CFStreamClientContext

的第二个参数，请查看我关于代码应该是什么样子的更新答案（假设Apple修复了编译器崩溃）