Concurrency Swift与Objective-C';s"@同步的;?
我搜索了Swift书籍,但找不到@synchronized的Swift版本。如何在Swift中实现互斥?您可以在Concurrency Swift与Objective-C';s"@同步的;?,concurrency,mutex,swift,Concurrency,Mutex,Swift,我搜索了Swift书籍,但找不到@synchronized的Swift版本。如何在Swift中实现互斥?您可以在objc\u sync\u enter(obj:AnyObject?和objc\u sync\u exit(obj:AnyObject?)之间夹杂语句。@synchronized关键字在幕后使用这些方法。i、 e objc_sync_enter(self) ... synchronized code ... objc_sync_exit(self) 你可以使用GCD。它比@synch
objc\u sync\u enter(obj:AnyObject?
和objc\u sync\u exit(obj:AnyObject?)之间夹杂语句。@synchronized关键字在幕后使用这些方法。i、 e
objc_sync_enter(self)
... synchronized code ...
objc_sync_exit(self)
你可以使用GCD。它比@synchronized
稍微详细一些,但可以作为替代:
let serialQueue = DispatchQueue(label: "com.test.mySerialQueue")
serialQueue.sync {
// code
}
我自己也在寻找这一点,并得出结论,swift内部还没有针对这一点的本地构造
我的确是根据我从Matt Bridges和其他人那里看到的一些代码编写了这个小助手函数
func synced(_ lock: Any, closure: () -> ()) {
objc_sync_enter(lock)
closure()
objc_sync_exit(lock)
}
用法非常简单
synced(self) {
println("This is a synchronized closure")
}
我发现了一个问题。此时,作为lock参数传入数组似乎会导致非常迟钝的编译器错误。否则,尽管它似乎按预期工作
Bitcast requires both operands to be pointer or neither
%26 = bitcast i64 %25 to %objc_object*, !dbg !378
LLVM ERROR: Broken function found, compilation aborted!
要添加返回函数,可以执行以下操作:
func synchronize<T>(lockObj: AnyObject!, closure: ()->T) -> T
{
objc_sync_enter(lockObj)
var retVal: T = closure()
objc_sync_exit(lockObj)
return retVal
}
另一种方法是创建一个超类,然后继承它。这样,您可以更直接地使用GCD
class Lockable {
let lockableQ:dispatch_queue_t
init() {
lockableQ = dispatch_queue_create("com.blah.blah.\(self.dynamicType)", DISPATCH_QUEUE_SERIAL)
}
func lock(closure: () -> ()) {
dispatch_sync(lockableQ, closure)
}
}
class Foo: Lockable {
func boo() {
lock {
....... do something
}
}
为什么要让锁变得困难和麻烦?
使用调度屏障
调度屏障在并发队列中创建同步点。
当它运行时,队列上的任何其他块都不允许运行,即使它是并发的并且其他核心可用。
如果这听起来像是一个独占(写)锁,那么它就是。
可以将非屏障块视为共享(读取)锁。
只要所有对资源的访问都是通过队列执行的,屏障就可以提供非常便宜的同步。我喜欢并使用这里的许多答案,所以我会选择最适合您的答案。也就是说,当我需要像objective-c的@synchronized
这样的东西时,我更喜欢的方法使用swift 2中介绍的语句
{
objc_sync_enter(lock)
defer { objc_sync_exit(lock) }
//
// code of critical section goes here
//
} // <-- lock released when this block is exited
{
objc_同步_输入(锁定)
延迟{objc_sync_exit(lock)}
//
//关键部分的代码在这里
//
}//使用Bryan McLemore的回答,我扩展了它,以支持在具有Swift 2.0延迟功能的安全庄园中放置的对象
func synchronized( lock:AnyObject, block:() throws -> Void ) rethrows
{
objc_sync_enter(lock)
defer {
objc_sync_exit(lock)
}
try block()
}
Objective-C指令的模拟在Swift中可以有任意的返回类型和良好的行为
// Swift 3
func synchronized<T>(_ lock: AnyObject, _ body: () throws -> T) rethrows -> T {
objc_sync_enter(lock)
defer { objc_sync_exit(lock) }
return try body()
}
根据GNewc(我喜欢任意返回类型)和Tod Cunningham(我喜欢延迟
)的答案,测试一个子类案例
class Foo: NSObject {
func test() {
print("1")
objc_sync_enter(self)
defer {
objc_sync_exit(self)
print("3")
}
print("2")
}
}
class Foo2: Foo {
override func test() {
super.test()
print("11")
objc_sync_enter(self)
defer {
print("33")
objc_sync_exit(self)
}
print("22")
}
}
let test = Foo2()
test.test()
输出:
dispatch\u barrier\u async是更好的方法,同时不阻塞当前线程
dispatch\u barrier\u async(访问队列{
字典[object.ID]=对象
})总之,这里给出了更常见的方法,包括返回值或void,以及抛出
import Foundation
extension NSObject {
func synchronized<T>(lockObj: AnyObject!, closure: () throws -> T) rethrows -> T
{
objc_sync_enter(lockObj)
defer {
objc_sync_exit(lockObj)
}
return try closure()
}
}
<代码>导入基础
扩展NSObject{
func synchronized(lockObj:AnyObject!),闭包:()抛出->T)重试->T
{
对象同步输入(锁定对象)
推迟{
objc_同步_退出(锁定OBJ)
}
返回try闭包()
}
}
SWIFT 4
在Swift 4中,您可以使用GCDs调度队列锁定资源
class MyObject {
private var internalState: Int = 0
private let internalQueue: DispatchQueue = DispatchQueue(label:"LockingQueue") // Serial by default
var state: Int {
get {
return internalQueue.sync { internalState }
}
set (newState) {
internalQueue.sync { internalState = newState }
}
}
}
Swift 3 此代码具有重入功能,可以处理异步函数调用。在这段代码中,调用someAsyncFunc()后,将处理串行队列上的另一个函数闭包,但会被信号量阻塞。请等待()直到调用signal()。不应使用internalQueue.sync,因为如果我没有弄错的话,它将阻止主线程
let internalQueue = DispatchQueue(label: "serialQueue")
let semaphore = DispatchSemaphore(value: 1)
internalQueue.async {
self.semaphore.wait()
// Critical section
someAsyncFunc() {
// Do some work here
self.semaphore.signal()
}
}
如果没有错误处理,objc_sync_enter/objc_sync_exit不是一个好主意。详细信息
代码8.3.1,Swift 3.1
任务
从不同线程读写值(异步)
代码
类视图控制器
导入UIKit
类ViewController:UIViewController{
重写func viewDidLoad(){
super.viewDidLoad()
//样本1()
样本2()
}
func样本1(){
打印(“带变量的样本”)
设obj=AsyncObject(值:0,dispatchQueueName:“Dispatch1”)
DispatchGroup.loop(repeatNumber:5,action:{index in
obj.value=索引
}) {
打印(“\(对象值)”)
}
}
func样本2(){
打印(“\n=========================================================================\n带阵列的采样”)
设arr=AsyncObject(值:[],dispatchQueueName:“Dispatch2”)
DispatchGroup.loop(repeatNumber:15,action:{index in
arr.setValue{(当前)->([Int])在
var数组=当前
array.append(索引*索引)
打印(“索引:\(索引),值\(数组[array.count-1]))
返回数组
}
}) {
打印(“\(arr.value)”)
}
}
}
在Swift4中使用:
let lock = NSLock()
lock.lock()
if isRunning == true {
print("Service IS running ==> please wait")
return
} else {
print("Service not running")
}
isRunning = true
lock.unlock()
警告
NSLock类使用POSIX线程来实现其锁定行为。向NSLock对象发送解锁消息时,必须确保该消息是从发送初始锁定消息的同一线程发送的。从不同线程解锁锁可能会导致未定义的行为
在2018年WWDC的“了解崩溃和崩溃日志”中,他们展示了使用带有同步的DispatchQueues的以下方法
在swift 4中,应类似于以下内容:
class ImageCache {
private let queue = DispatchQueue(label: "sync queue")
private var storage: [String: UIImage] = [:]
public subscript(key: String) -> UIImage? {
get {
return queue.sync {
return storage[key]
}
}
set {
queue.sync {
storage[key] = newValue
}
}
}
}
无论如何,您也可以使用带屏障的并发队列加快读取速度。同步和异步读取同时执行,写入新值将等待以前的操作完成
class ImageCache {
private let queue = DispatchQueue(label: "with barriers", attributes: .concurrent)
private var storage: [String: UIImage] = [:]
func get(_ key: String) -> UIImage? {
return queue.sync { [weak self] in
guard let self = self else { return nil }
return self.storage[key]
}
}
func set(_ image: UIImage, for key: String) {
queue.async(flags: .barrier) { [weak self] in
guard let self = self else { return }
self.storage[key] = image
}
}
}
图我将发布我的Swift 5实现,基于之前的答案。谢谢大家!我发现有一个返回值的方法也很有用,所以我有两个方法 下面是一个简单的类:
import Foundation
class Sync {
public class func synced(_ lock: Any, closure: () -> ()) {
objc_sync_enter(lock)
defer { objc_sync_exit(lock) }
closure()
}
public class func syncedReturn(_ lock: Any, closure: () -> (Any?)) -> Any? {
objc_sync_enter(lock)
defer { objc_sync_exit(lock) }
return closure()
}
}
然后,如果需要返回值,也可以这样使用:
return Sync.syncedReturn(self, closure: {
// some code here
return "hello world"
})
或:
尝试:
同一线程可以多次获取的锁,无需
造成僵局的
Objective-C同步功能支持
extension DispatchGroup {
class func loop(repeatNumber: Int, action: @escaping (_ index: Int)->(), completion: @escaping ()->()) {
let group = DispatchGroup()
for index in 0...repeatNumber {
group.enter()
DispatchQueue.global(qos: .utility).async {
action(index)
group.leave()
}
}
group.notify(queue: DispatchQueue.global(qos: .userInitiated)) {
completion()
}
}
}
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
//sample1()
sample2()
}
func sample1() {
print("=================================================\nsample with variable")
let obj = AsyncObject<Int>(value: 0, dispatchQueueName: "Dispatch1")
DispatchGroup.loop(repeatNumber: 5, action: { index in
obj.value = index
}) {
print("\(obj.value)")
}
}
func sample2() {
print("\n=================================================\nsample with array")
let arr = AsyncObject<[Int]>(value: [], dispatchQueueName: "Dispatch2")
DispatchGroup.loop(repeatNumber: 15, action: { index in
arr.setValue{ (current) -> ([Int]) in
var array = current
array.append(index*index)
print("index: \(index), value \(array[array.count-1])")
return array
}
}) {
print("\(arr.value)")
}
}
}
let lock = NSLock()
lock.lock()
if isRunning == true {
print("Service IS running ==> please wait")
return
} else {
print("Service not running")
}
isRunning = true
lock.unlock()
class ImageCache {
private let queue = DispatchQueue(label: "sync queue")
private var storage: [String: UIImage] = [:]
public subscript(key: String) -> UIImage? {
get {
return queue.sync {
return storage[key]
}
}
set {
queue.sync {
storage[key] = newValue
}
}
}
}
class ImageCache {
private let queue = DispatchQueue(label: "with barriers", attributes: .concurrent)
private var storage: [String: UIImage] = [:]
func get(_ key: String) -> UIImage? {
return queue.sync { [weak self] in
guard let self = self else { return nil }
return self.storage[key]
}
}
func set(_ image: UIImage, for key: String) {
queue.async(flags: .barrier) { [weak self] in
guard let self = self else { return }
self.storage[key] = image
}
}
}
import Foundation
class Sync {
public class func synced(_ lock: Any, closure: () -> ()) {
objc_sync_enter(lock)
defer { objc_sync_exit(lock) }
closure()
}
public class func syncedReturn(_ lock: Any, closure: () -> (Any?)) -> Any? {
objc_sync_enter(lock)
defer { objc_sync_exit(lock) }
return closure()
}
}
return Sync.syncedReturn(self, closure: {
// some code here
return "hello world"
})
Sync.synced(self, closure: {
// do some work synchronously
})
let lock = NSRecursiveLock()
func f() {
lock.lock()
//Your Code
lock.unlock()
}
func f2() {
lock.lock()
defer {
lock.unlock()
}
//Your Code
}
/**
Makes sure no other thread reenters the closure before the one running has not returned
*/
@discardableResult
public func synchronized<T>(_ lock: AnyObject, closure:() -> T) -> T {
objc_sync_enter(lock)
defer { objc_sync_exit(lock) }
return closure()
}
let returnedValue = synchronized(self) {
// Your code here
return yourCode()
}
synchronized(self) {
// Your code here
yourCode()
}
@NCCSerialized var foo: Int = 10
@NCCSerialized var myData: [SomeStruct] = []