Swift 取消NSO操作中包装的Alamofire请求会导致多个KVO?
我的Xcode版本:6.3.2Swift 取消NSO操作中包装的Alamofire请求会导致多个KVO?,swift,cocoa,alamofire,Swift,Cocoa,Alamofire,我的Xcode版本:6.3.2 Alamofire版本:1.2.2(通过Cocoapods安装) 为了设置maxConcurrentOperationCount以限制NSOperationQueue中的并发操作数,我将下载请求包装在NSOperation中 NSOperation的基本子类如下: class ConcurrentOperation : NSOperation { override var concurrent: Bool { return true
Alamofire版本:1.2.2(通过Cocoapods安装) 为了设置
maxConcurrentOperationCount
以限制NSOperationQueue
中的并发操作数,我将下载请求包装在NSOperation中
NSOperation
的基本子类如下:
class ConcurrentOperation : NSOperation {
override var concurrent: Bool {
return true
}
override var asynchronous: Bool {
return true
}
private var _executing: Bool = false
override var executing: Bool {
get {
return _executing
}
set {
if (_executing != newValue) {
self.willChangeValueForKey("isExecuting")
_executing = newValue
self.didChangeValueForKey("isExecuting")
}
}
}
private var _finished: Bool = false;
override var finished: Bool {
get {
return _finished
}
set {
if (_finished != newValue) {
self.willChangeValueForKey("isFinished")
_finished = newValue
self.didChangeValueForKey("isFinished")
}
}
}
/// Complete the operation
///
/// This will result in the appropriate KVN of isFinished and isExecuting
func completeOperation() {
executing = false
finished = true
}
override func start() {
if (cancelled) {
finished = true
return
}
executing = true
main()
}
}
class DownloadImageOperation : ConcurrentOperation {
let URLString: String
let downloadImageCompletionHandler: (responseObject: AnyObject?, error: NSError?) -> ()
weak var request: Alamofire.Request?
init(URLString: String, downloadImageCompletionHandler: (responseObject: AnyObject?, error: NSError?) -> ()) {
self.URLString = URLString
self.downloadImageCompletionHandler = downloadImageCompletionHandler
super.init()
}
override func main() {
let destination = Alamofire.Request.suggestedDownloadDestination(directory: .DocumentDirectory, domain: .UserDomainMask)
request = Alamofire.download(.GET, URLString, destination).response { (request, response, responseObject, error) in
if self.cancelled {
println("Alamofire.download cancelled while downlading. Not proceed.")
} else {
self.downloadImageCompletionHandler(responseObject: responseObject, error: error)
}
self.completeOperation()
}
}
override func cancel() {
request?.cancel()
super.cancel()
}
}
func downloadImages() {
let imgLinks = [
"https://farm4.staticflickr.com/3925/18769503068_1fc09427ec_k.jpg",
"https://farm1.staticflickr.com/338/18933828356_4f57420df7_k.jpg",
"https://farm4.staticflickr.com/3776/18945113685_ccec89d67a_o.jpg",
"https://farm1.staticflickr.com/366/18333992053_725f21166e_k.jpg",
"https://farm4.staticflickr.com/3777/18962702032_086453ee7a_k.jpg",
"https://farm1.staticflickr.com/373/18930501406_4753ac021a_k.jpg",
"https://farm1.staticflickr.com/283/18772907409_56ffbe573b_k.jpg",
"https://farm1.staticflickr.com/314/18940901785_b0564b1c9b_o.jpg",
"https://farm1.staticflickr.com/502/18949263495_88d75d2d2f_k.jpg",
"https://farm4.staticflickr.com/3912/18938184302_6e0ca9ad31_k.jpg",
"https://farm1.staticflickr.com/356/18957923475_3dc9df7634_k.jpg",
"https://farm1.staticflickr.com/378/18925014986_e87feca9c7_o.jpg",
"https://farm1.staticflickr.com/461/18949863812_ddf700bd03_o.jpg",
"https://farm1.staticflickr.com/303/18920711216_4684ff4295_k.jpg",
"https://farm1.staticflickr.com/558/18935058546_fc10d10855_k.jpg",
"https://farm1.staticflickr.com/384/18955290345_fb93d17828_o.jpg",
"https://farm1.staticflickr.com/366/18333992053_725f21166e_k.jpg",
"https://farm4.staticflickr.com/3777/18962702032_086453ee7a_k.jpg",
"https://farm1.staticflickr.com/373/18930501406_4753ac021a_k.jpg",
"https://farm1.staticflickr.com/283/18772907409_56ffbe573b_k.jpg",
"https://farm1.staticflickr.com/314/18940901785_b0564b1c9b_o.jpg",
"https://farm1.staticflickr.com/502/18949263495_88d75d2d2f_k.jpg",
"https://farm4.staticflickr.com/3912/18938184302_6e0ca9ad31_k.jpg",
"https://farm1.staticflickr.com/356/18957923475_3dc9df7634_k.jpg",
"https://farm1.staticflickr.com/378/18925014986_e87feca9c7_o.jpg",
"https://farm1.staticflickr.com/461/18949863812_ddf700bd03_o.jpg",
"https://farm1.staticflickr.com/303/18920711216_4684ff4295_k.jpg",
"https://farm1.staticflickr.com/558/18935058546_fc10d10855_k.jpg",
"https://farm1.staticflickr.com/366/18333992053_725f21166e_k.jpg",
"https://farm4.staticflickr.com/3777/18962702032_086453ee7a_k.jpg",
"https://farm1.staticflickr.com/373/18930501406_4753ac021a_k.jpg",
"https://farm1.staticflickr.com/283/18772907409_56ffbe573b_k.jpg",
"https://farm1.staticflickr.com/314/18940901785_b0564b1c9b_o.jpg",
"https://farm1.staticflickr.com/502/18949263495_88d75d2d2f_k.jpg",
"https://farm4.staticflickr.com/3912/18938184302_6e0ca9ad31_k.jpg",
"https://farm1.staticflickr.com/356/18957923475_3dc9df7634_k.jpg",
"https://farm1.staticflickr.com/378/18925014986_e87feca9c7_o.jpg",
"https://farm1.staticflickr.com/461/18949863812_ddf700bd03_o.jpg",
"https://farm1.staticflickr.com/303/18920711216_4684ff4295_k.jpg",
"https://farm1.staticflickr.com/558/18935058546_fc10d10855_k.jpg",
"https://farm4.staticflickr.com/3777/18962702032_086453ee7a_k.jpg",
"https://farm1.staticflickr.com/373/18930501406_4753ac021a_k.jpg",
"https://farm1.staticflickr.com/283/18772907409_56ffbe573b_k.jpg",
"https://farm1.staticflickr.com/314/18940901785_b0564b1c9b_o.jpg",
"https://farm1.staticflickr.com/502/18949263495_88d75d2d2f_k.jpg",
"https://farm4.staticflickr.com/3912/18938184302_6e0ca9ad31_k.jpg",
"https://farm1.staticflickr.com/356/18957923475_3dc9df7634_k.jpg",
"https://farm1.staticflickr.com/378/18925014986_e87feca9c7_o.jpg",
"https://farm1.staticflickr.com/461/18949863812_ddf700bd03_o.jpg",
"https://farm1.staticflickr.com/303/18920711216_4684ff4295_k.jpg",
"https://farm1.staticflickr.com/558/18935058546_fc10d10855_k.jpg",
"https://farm1.staticflickr.com/266/18956724112_6e61a743a5_k.jpg"
]
var testAlamofireObserver = TestAlamofireObserver()
testAlamofireObserver!.queue.maxConcurrentOperationCount = 5
for imgLink in imgLinks {
let operation = DownloadImageOperation(URLString: imgLink) {
(responseObject, error) in
if responseObject == nil {
// handle error here
println("failed: \(error)")
} else {
println("\(responseObject?.absoluteString) downloaded.")
}
}
testAlamofireObserver!.queue.addOperation(operation)
}
}
我的子类包装Alamofire下载请求,如下所示:
class ConcurrentOperation : NSOperation {
override var concurrent: Bool {
return true
}
override var asynchronous: Bool {
return true
}
private var _executing: Bool = false
override var executing: Bool {
get {
return _executing
}
set {
if (_executing != newValue) {
self.willChangeValueForKey("isExecuting")
_executing = newValue
self.didChangeValueForKey("isExecuting")
}
}
}
private var _finished: Bool = false;
override var finished: Bool {
get {
return _finished
}
set {
if (_finished != newValue) {
self.willChangeValueForKey("isFinished")
_finished = newValue
self.didChangeValueForKey("isFinished")
}
}
}
/// Complete the operation
///
/// This will result in the appropriate KVN of isFinished and isExecuting
func completeOperation() {
executing = false
finished = true
}
override func start() {
if (cancelled) {
finished = true
return
}
executing = true
main()
}
}
class DownloadImageOperation : ConcurrentOperation {
let URLString: String
let downloadImageCompletionHandler: (responseObject: AnyObject?, error: NSError?) -> ()
weak var request: Alamofire.Request?
init(URLString: String, downloadImageCompletionHandler: (responseObject: AnyObject?, error: NSError?) -> ()) {
self.URLString = URLString
self.downloadImageCompletionHandler = downloadImageCompletionHandler
super.init()
}
override func main() {
let destination = Alamofire.Request.suggestedDownloadDestination(directory: .DocumentDirectory, domain: .UserDomainMask)
request = Alamofire.download(.GET, URLString, destination).response { (request, response, responseObject, error) in
if self.cancelled {
println("Alamofire.download cancelled while downlading. Not proceed.")
} else {
self.downloadImageCompletionHandler(responseObject: responseObject, error: error)
}
self.completeOperation()
}
}
override func cancel() {
request?.cancel()
super.cancel()
}
}
func downloadImages() {
let imgLinks = [
"https://farm4.staticflickr.com/3925/18769503068_1fc09427ec_k.jpg",
"https://farm1.staticflickr.com/338/18933828356_4f57420df7_k.jpg",
"https://farm4.staticflickr.com/3776/18945113685_ccec89d67a_o.jpg",
"https://farm1.staticflickr.com/366/18333992053_725f21166e_k.jpg",
"https://farm4.staticflickr.com/3777/18962702032_086453ee7a_k.jpg",
"https://farm1.staticflickr.com/373/18930501406_4753ac021a_k.jpg",
"https://farm1.staticflickr.com/283/18772907409_56ffbe573b_k.jpg",
"https://farm1.staticflickr.com/314/18940901785_b0564b1c9b_o.jpg",
"https://farm1.staticflickr.com/502/18949263495_88d75d2d2f_k.jpg",
"https://farm4.staticflickr.com/3912/18938184302_6e0ca9ad31_k.jpg",
"https://farm1.staticflickr.com/356/18957923475_3dc9df7634_k.jpg",
"https://farm1.staticflickr.com/378/18925014986_e87feca9c7_o.jpg",
"https://farm1.staticflickr.com/461/18949863812_ddf700bd03_o.jpg",
"https://farm1.staticflickr.com/303/18920711216_4684ff4295_k.jpg",
"https://farm1.staticflickr.com/558/18935058546_fc10d10855_k.jpg",
"https://farm1.staticflickr.com/384/18955290345_fb93d17828_o.jpg",
"https://farm1.staticflickr.com/366/18333992053_725f21166e_k.jpg",
"https://farm4.staticflickr.com/3777/18962702032_086453ee7a_k.jpg",
"https://farm1.staticflickr.com/373/18930501406_4753ac021a_k.jpg",
"https://farm1.staticflickr.com/283/18772907409_56ffbe573b_k.jpg",
"https://farm1.staticflickr.com/314/18940901785_b0564b1c9b_o.jpg",
"https://farm1.staticflickr.com/502/18949263495_88d75d2d2f_k.jpg",
"https://farm4.staticflickr.com/3912/18938184302_6e0ca9ad31_k.jpg",
"https://farm1.staticflickr.com/356/18957923475_3dc9df7634_k.jpg",
"https://farm1.staticflickr.com/378/18925014986_e87feca9c7_o.jpg",
"https://farm1.staticflickr.com/461/18949863812_ddf700bd03_o.jpg",
"https://farm1.staticflickr.com/303/18920711216_4684ff4295_k.jpg",
"https://farm1.staticflickr.com/558/18935058546_fc10d10855_k.jpg",
"https://farm1.staticflickr.com/366/18333992053_725f21166e_k.jpg",
"https://farm4.staticflickr.com/3777/18962702032_086453ee7a_k.jpg",
"https://farm1.staticflickr.com/373/18930501406_4753ac021a_k.jpg",
"https://farm1.staticflickr.com/283/18772907409_56ffbe573b_k.jpg",
"https://farm1.staticflickr.com/314/18940901785_b0564b1c9b_o.jpg",
"https://farm1.staticflickr.com/502/18949263495_88d75d2d2f_k.jpg",
"https://farm4.staticflickr.com/3912/18938184302_6e0ca9ad31_k.jpg",
"https://farm1.staticflickr.com/356/18957923475_3dc9df7634_k.jpg",
"https://farm1.staticflickr.com/378/18925014986_e87feca9c7_o.jpg",
"https://farm1.staticflickr.com/461/18949863812_ddf700bd03_o.jpg",
"https://farm1.staticflickr.com/303/18920711216_4684ff4295_k.jpg",
"https://farm1.staticflickr.com/558/18935058546_fc10d10855_k.jpg",
"https://farm4.staticflickr.com/3777/18962702032_086453ee7a_k.jpg",
"https://farm1.staticflickr.com/373/18930501406_4753ac021a_k.jpg",
"https://farm1.staticflickr.com/283/18772907409_56ffbe573b_k.jpg",
"https://farm1.staticflickr.com/314/18940901785_b0564b1c9b_o.jpg",
"https://farm1.staticflickr.com/502/18949263495_88d75d2d2f_k.jpg",
"https://farm4.staticflickr.com/3912/18938184302_6e0ca9ad31_k.jpg",
"https://farm1.staticflickr.com/356/18957923475_3dc9df7634_k.jpg",
"https://farm1.staticflickr.com/378/18925014986_e87feca9c7_o.jpg",
"https://farm1.staticflickr.com/461/18949863812_ddf700bd03_o.jpg",
"https://farm1.staticflickr.com/303/18920711216_4684ff4295_k.jpg",
"https://farm1.staticflickr.com/558/18935058546_fc10d10855_k.jpg",
"https://farm1.staticflickr.com/266/18956724112_6e61a743a5_k.jpg"
]
var testAlamofireObserver = TestAlamofireObserver()
testAlamofireObserver!.queue.maxConcurrentOperationCount = 5
for imgLink in imgLinks {
let operation = DownloadImageOperation(URLString: imgLink) {
(responseObject, error) in
if responseObject == nil {
// handle error here
println("failed: \(error)")
} else {
println("\(responseObject?.absoluteString) downloaded.")
}
}
testAlamofireObserver!.queue.addOperation(operation)
}
}
它覆盖cancel()
,并在取消NSOperation
时尝试取消Alamofire请求
我使用KVO观察器观察NSOperationQueue
的完成情况
private var testAlamofireContext = 0
class TestAlamofireObserver: NSObject {
var queue = NSOperationQueue()
init(delegate: ImageDownloadDelegate) {
super.init()
queue.addObserver(self, forKeyPath: "operations", options: .New, context: &testAlamofireContext)
}
deinit {
queue.removeObserver(self, forKeyPath: "operations", context: &testAlamofireContext)
}
override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject, change: [NSObject: AnyObject], context: UnsafeMutablePointer<Void>) {
if context == &testAlamofireContext {
if self.queue.operations.count == 0 {
println("Image Download Complete queue. keyPath: \(keyPath); object: \(object); context: \(context)")
}
} else {
super.observeValueForKeyPath(keyPath, ofObject: object, change: change, context: context)
}
}
}
如果队列在未收到任何取消的情况下完成,则日志输出应为:
2015-06-22 17:11:04.206 RSS Wallpaper Switchr[46250:714702] Optional(Optional("https://farm1.staticflickr.com/461/18949863812_ddf700bd03_o.jpg")) downloaded.
...
...
...
2015-06-22 17:11:56.979 RSS Wallpaper Switchr[46250:714702] Optional(Optional("https://farm1.staticflickr.com/461/18949863812_ddf700bd03_o.jpg")) downloaded.
2015-06-22 17:11:56.979 RSS Wallpaper Switchr[46250:714702] Image Download Complete queue. keyPath: operations; object: <NSOperationQueue: 0x6180002354a0>{name = 'NSOperationQueue 0x6180002354a0'}; context: 0x000000010007eb70
但是,如果我如上所述将maxConcurrentOperationCount
更改为非默认值,并且队列接收到cancelAllOperations()
,则日志变为:
2015-06-22 17:17:56.427 RSS Wallpaper Switchr[46606:722523] Optional(Optional("https://farm4.staticflickr.com/3777/18962702032_086453ee7a_k.jpg")) downloaded.
2015-06-22 17:17:58.675 RSS Wallpaper Switchr[46606:722523] Alamofire.download cancelled while downlading. Not proceed.
...
...
2015-06-22 17:17:58.677 RSS Wallpaper Switchr[46606:722523] Alamofire.download cancelled while downlading. Not proceed.
2015-06-22 17:17:58.678 RSS Wallpaper Switchr[46606:722720] Image Download Complete queue. keyPath: operations; object: <NSOperationQueue: 0x608000424ee0>{name = 'NSOperationQueue 0x608000424ee0'}; context: 0x000000010007eb70
2015-06-22 17:17:58.678 RSS Wallpaper Switchr[46606:722560] Image Download Complete queue. keyPath: operations; object: <NSOperationQueue: 0x608000424ee0>{name = 'NSOperationQueue 0x608000424ee0'}; context: 0x000000010007eb70
2015-06-22 17:17:58.678 RSS Wallpaper Switchr[46606:722574] Image Download Complete queue. keyPath: operations; object: <NSOperationQueue: 0x608000424ee0>{name = 'NSOperationQueue 0x608000424ee0'}; context: 0x000000010007eb70
2015-06-22 17:17:58.678 RSS Wallpaper Switchr[46606:722719] Image Download Complete queue. keyPath: operations; object: <NSOperationQueue: 0x608000424ee0>{name = 'NSOperationQueue 0x608000424ee0'}; context: 0x000000010007eb70
2015-06-22 17:17:58.678 RSS Wallpaper Switchr[46606:722721] Image Download Complete queue. keyPath: operations; object: <NSOperationQueue: 0x608000424ee0>{name = 'NSOperationQueue 0x608000424ee0'}; context: 0x000000010007eb70
2015-06-22 17:17:58.678 RSS Wallpaper Switchr[46606:722572] Image Download Complete queue. keyPath: operations; object: <NSOperationQueue: 0x608000424ee0>{name = 'NSOperationQueue 0x608000424ee0'}; context: 0x000000010007eb70
2015-06-22 17:17:56.427 RSS墙纸开关[46606:722523]可选https://farm4.staticflickr.com/3777/18962702032_086453ee7a_k.jpg)下载。
2015-06-22 17:17:58.675下载时取消RSS墙纸切换[46606:722523]Alamofire.download。不继续。
...
...
2015-06-22 17:17:58.677下载时取消RSS墙纸切换[46606:722523]Alamofire.download。不继续。
2015-06-22 17:17:58.678 RSS墙纸切换器[46606:722720]图像下载完成队列。关键路径:操作;对象:{name='NSOperationQueue 0x60800424EE0'};上下文:0x000000010007eb70
2015-06-22 17:17:58.678 RSS墙纸切换器[46606:722560]图像下载完成队列。关键路径:操作;对象:{name='NSOperationQueue 0x60800424EE0'};上下文:0x000000010007eb70
2015-06-22 17:17:58.678 RSS墙纸切换器[46606:722574]图像下载完成队列。关键路径:操作;对象:{name='NSOperationQueue 0x60800424EE0'};上下文:0x000000010007eb70
2015-06-22 17:17:58.678 RSS墙纸切换器[46606:722719]图像下载完成队列。关键路径:操作;对象:{name='NSOperationQueue 0x60800424EE0'};上下文:0x000000010007eb70
2015-06-22 17:17:58.678 RSS墙纸切换器[46606:722721]图像下载完成队列。关键路径:操作;对象:{name='NSOperationQueue 0x60800424EE0'};上下文:0x000000010007eb70
2015-06-22 17:17:58.678 RSS墙纸切换器[46606:722572]图像下载完成队列。关键路径:操作;对象:{name='NSOperationQueue 0x60800424EE0'};上下文:0x000000010007eb70
KVOobserveValueForKeyPath
是从多个不同的线程执行的。线程的数量可能是可变的。这将导致多次执行KVO的完成功能。如果我不更改默认值maxConcurrentOperationCount
或不更改request?.cancel()
forAlamofire.request
,则不会发生这种情况
为什么我关心KVO完成函数的多次执行?我的目的是启动一个下载队列,当足够的下载完成时,取消剩余的操作,即使是未启动或正在下载的操作,然后为下载做一些事情。完成函数应该只执行一次,有两个因素(1)更改默认的
maxConcurrentOperationCount
(2)不request?.cancel()
用于Alamofire.request
可能与之相关。我想知道为什么以及如何纠正这一点。我不认为您描述的多重KVN行为令人惊讶。文档中没有任何内容表明,当它取消所有操作时,将导致操作
上的单个KVN。事实上,你可以有把握地推断出你所描述的行为应该是预期的(因为它不会先发制人地杀死所有这些工作线程,而是向每个线程发送一条cancel
消息,每个操作负责在自己的时间内响应该消息;我不希望在操作最终实际完成之前更新操作
)
就个人而言,我建议完全停用此观察者模式。您的代码不应取决于NSOperationQueue
是否一次删除所有操作。我建议您改为依赖现有的downloadImageCompletionHandler
闭包,称之为请求是否完成或者不是。只需让闭包查看错误
对象,以确定它是否已被取消,或者是否由于其他原因失败
如果您想知道所有这些操作何时完成,我不会依赖于
operations
KVN。相反,我可能会根据所有其他请求创建一个完成操作:
let completionOperation = NSBlockOperation() { // create completion operation
// do whatever you want here
}
for imgLink in imgLinks {
let operation = DownloadImageOperation(URLString: imgLink) { responseObject, error in
if error != nil {
if error!.code == NSURLErrorCancelled && error!.domain == NSURLErrorDomain {
println("everything OK, just canceled")
} else {
println("error=\(error)")
}
}
if responseObject != nil {
println("\(responseObject?.absoluteString) downloaded.")
}
}
completionOperation.addDependency(operation) // add dependency
testAlamofireObserver!.queue.addOperation(operation)
}
NSOperationQueue.mainQueue().addOperation(completionOperation) // schedule completion operation on some other queue (so that when I cancel everything on that other queue, I don't cancel this, too)
AlamoFire看起来非常简单。我认为问题不在那里。谢谢Rob。我用
NSLog
替换了println
,然后日志输出更加合理。但是,我提供的代码可能会遗漏一个关键点。(请参阅我在上述问题中的编辑。)我发现,如果我为NSOperationQueue
设置maxConcurrentOperationCount
,取消操作将导致奇怪的行为。但是,请忘记前面提到的非特定NSZombie
对象和过度释放的非特定对象。这可能是由于上面未显示的其他代码造成的。问题已解决。我已修改回答这个问题。我想cancel()
仅适用于NSOperation
包装Alamofire。它不应更改NSOperationQueue
的行为。因此,不应更改NSOperationQueue
的KVO观察员的行为。感谢您的建议。我将考虑使用downloadImageCompletionHandler
闭包。但是,我仍然不理解如何以及为什么maxConcurrentOperationCount
和请求?.cancel()
与每个