[英]Modifying struct instance variables within a Dispatch closure in Swift
I'm using the DEVELOPMENT-SNAPSHOT-2016-06-06-a
version of Swift. 我正在使用
DEVELOPMENT-SNAPSHOT-2016-06-06-a
版本的Swift。 I cannot seem to get around this issue, I've tried using @noescape
in various places, but I still have the following error: 我似乎
@noescape
这个问题,我尝试在各个地方使用@noescape
,但我仍然有以下错误:
Closure cannot implicitly capture a mutating self parameter
闭包不能隐式捕获变异的自身参数
To better explain, here is a simple example: 为了更好地解释,这是一个简单的例子:
public struct ExampleStruct {
let connectQueue = dispatch_queue_create("connectQueue", nil)
var test = 10
mutating func example() {
if let connectQueue = self.connectQueue {
dispatch_sync(connectQueue) {
self.test = 20 // error happens here
}
}
}
}
Something must have changed in these Swift binaries that is now causing my previously working code to break. 这些Swift二进制文件中的某些东西必须已经改变,现在导致我以前工作的代码中断了。 A workaround I want to avoid is making my struct a class, which does help in fixing the issue.
我想避免的一种解决方法是使我的结构体成为一个类,这有助于解决问题。 Let me know if there is another way.
如果还有其他方法,请告诉我。
I cannot test it, because I'm not using a build with that error, but I'm pretty sure by capturing self explicitly you can fix it: 我无法测试它,因为我没有使用的生成与该错误,但我通过捕捉自我明确 ,你可以解决它很肯定:
dispatch_sync(connectQueue) { [self] in
self.test = 20
}
EDIT: Apparently it doesn't work, maybe you can try this (not very nice tbh): 编辑:显然它不起作用,也许你可以尝试这个(不是很好tbh):
var copy = self
dispatch_sync(connectQueue) {
copy.test = 20
}
self = copy
If you want to read more on why, here is the responsible Swift proposal . 如果您想了解更多关于原因的信息,请参阅负责的Swift提案 。
The new dispatch API makes the sync
method @noreturn
so you wouldn't need the explicit capture: 新的调度API使
sync
方法@noreturn
因此您不需要显式捕获:
connectQueue.sync {
test = 20
}
You are using Swift3 since you mentioned a recent dev snapshot
of Swift
. 您正在使用Swift3,因为您提到了最近的
Swift
dev snapshot
。 Try below and let me know if it works: 请尝试以下操作,让我知道它是否有效:
public struct ExampleStruct {
let connectQueue = DispatchQueue(label: "connectQueue", attributes: .concurrent)//This creates a concurrent Queue
var test = 10
mutating func example() {
connectQueue.sync {
self.test = 20
}
}
}
If you are interested in other types of queues, check these: 如果您对其他类型的队列感兴趣,请检查以下内容:
let serialQueue = DispatchQueue(label: "YOUR_QUEUE", attributes: .serial)
serialQueue.sync {
//
}
Get the mainQueue
asynchronously and synchronously: 以异步和同步方式获取
mainQueue
:
DispatchQueue.main.async {
//async operations
}
DispatchQueue.main.sync {
//sync operations
}
And if you are interested in Background: 如果你对背景感兴趣:
DispatchQueue.global(attributes: .qosDefault).async {
//async operations
}
You could refer this for new features in Swift3 and for changes to existing version: Migrating to Swift 2.3 or Swift 3 from Swift 2.2 你可以参考这个来获取Swift3中的新功能以及对现有版本的更改: 从Swift 2.2迁移到Swift 2.3或Swift 3
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.