本文简要介绍如何使用KVO 跟踪NSOperation 状态
traceOperation 方法跟踪 PageLoadOperation（NSOperation 子类）
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after app launch
for (NSString *urlString in urlArray)
{
NSURL *url = [NSURL URLWithString:urlString];
PageLoadOperation *plo = [[PageLoadOperation alloc] initWithURL:url];
[queue addOperation:plo];
[self traceOperation:plo];
[plo release];
}
[window addSubview:viewController.view];
[window makeKeyAndVisible];
return YES;
}
traceOperation 方法
KVO-Compliant Properties
The NSOperation class is key-value coding (KVC) and key-value observing (KVO) compliant for several of its properties. As needed, you can observe these properties to control other parts of your application. The properties you can observe include the following:
isCancelled- read-only propertyisConcurrent- read-only propertyisExecuting- read-only propertyisFinished- read-only propertyisReady- read-only propertydependencies- read-only propertyqueuePriority- readable and writable propertycompletionBlock- readable and writable property (Mac OS X only)
-(void)traceOperation:(NSOperation*)obj
{
[obj addObserver:self
forKeyPath:@"isExecuting"
options:0
context:NULL];
[obj addObserver:self
forKeyPath:@"isFinished"
options:0
context:NULL];
[obj addObserver:self
forKeyPath:@"isReady"
options:0
context:NULL];
[obj addObserver:self
forKeyPath:@"isCancelled"
options:0
context:NULL];
}
#pragma mark -
#pragma mark KVO 回调方法
- (void)observeValueForKeyPath:(NSString *)keyPath
ofObject:(id)object
change:(NSDictionary *)change
context:(void *)context
{
NSLog(@"dict= %@ obj= %@,keypath=%@",change,object,keyPath);
}
NSOperation 完成后回调方法,执行完第一个下载，cancel所有
- (void)pageLoaded:(NSString*)document;
{
NSLog(@"%s Do something with the XMLDocument", _cmd);
for (id opt in [queue operations]) {
NSLog(@"opt:%@ will cancel",opt);
[(NSOperation*)opt cancel];
}
}
执行log如下
[Session started at 2010-05-25 13:31:26 +0800.]
2010-05-25 13:31:28.030 AsyncDownloader[2672:4503] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x3b0a530>,keypath=isExecuting
2010-05-25 13:31:28.032 AsyncDownloader[2672:4903] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x390dc00>,keypath=isExecuting
2010-05-25 13:31:28.490 AsyncDownloader[2672:207] pageLoaded: Do something with the XMLDocument
2010-05-25 13:31:28.490 AsyncDownloader[2672:4903] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x390dc00>,keypath=isExecuting
2010-05-25 13:31:28.490 AsyncDownloader[2672:207] opt:<PageLoadOperation: 0x3b0a530> will cancel
2010-05-25 13:31:28.494 AsyncDownloader[2672:207] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x3b0a530>,keypath=isCancelled
2010-05-25 13:31:28.495 AsyncDownloader[2672:207] opt:<PageLoadOperation: 0x390dc00> will cancel
2010-05-25 13:31:28.495 AsyncDownloader[2672:4903] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x390dc00>,keypath=isFinished
2010-05-25 13:31:28.495 AsyncDownloader[2672:6607] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x3912ae0>,keypath=isExecuting
2010-05-25 13:31:28.496 AsyncDownloader[2672:207] opt:<PageLoadOperation: 0x3912ae0> will cancel
2010-05-25 13:31:28.496 AsyncDownloader[2672:207] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x3912ae0>,keypath=isCancelled
2010-05-25 13:31:28.497 AsyncDownloader[2672:207] opt:<PageLoadOperation: 0x3913470> will cancel
2010-05-25 13:31:28.497 AsyncDownloader[2672:207] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x3913470>,keypath=isCancelled
2010-05-25 13:31:28.498 AsyncDownloader[2672:207] opt:<PageLoadOperation: 0x39135f0> will cancel
2010-05-25 13:31:28.499 AsyncDownloader[2672:207] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x39135f0>,keypath=isCancelled
2010-05-25 13:31:28.916 AsyncDownloader[2672:207] pageLoaded: Do something with the XMLDocument
2010-05-25 13:31:28.916 AsyncDownloader[2672:207] opt:<PageLoadOperation: 0x3b0a530> will cancel
2010-05-25 13:31:28.916 AsyncDownloader[2672:207] opt:<PageLoadOperation: 0x3912ae0> will cancel
2010-05-25 13:31:28.916 AsyncDownloader[2672:207] opt:<PageLoadOperation: 0x3913470> will cancel
2010-05-25 13:31:28.916 AsyncDownloader[2672:207] opt:<PageLoadOperation: 0x39135f0> will cancel
2010-05-25 13:31:28.916 AsyncDownloader[2672:4503] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x3b0a530>,keypath=isExecuting
2010-05-25 13:31:28.918 AsyncDownloader[2672:4503] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x3b0a530>,keypath=isFinished
2010-05-25 13:31:28.920 AsyncDownloader[2672:5a33] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x3913470>,keypath=isFinished
2010-05-25 13:31:28.922 AsyncDownloader[2672:4507] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x39135f0>,keypath=isFinished
2010-05-25 13:31:30.652 AsyncDownloader[2672:6607] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x3912ae0>,keypath=isExecuting
2010-05-25 13:31:30.652 AsyncDownloader[2672:207] pageLoaded: Do something with the XMLDocument
2010-05-25 13:31:30.653 AsyncDownloader[2672:207] opt:<PageLoadOperation: 0x3912ae0> will cancel
2010-05-25 13:31:30.654 AsyncDownloader[2672:6607] dict= {
kind = 1;
} obj= <PageLoadOperation: 0x3912ae0>,keypath=isFinished
测试项目代码下载 AsyncDownloader.zip
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