【发布时间】：2011-03-15 05:42:33
【问题描述】：
我有一些主要是数据驱动的应用程序，因此大多数屏幕基本上由以下部分组成：
- 打开屏幕
- 通过 NSOperation 下载数据
- 在 UITableView 中显示数据
- 从 UITableView 中进行选择
- 进入新屏幕，从第 1 步重新开始
我发现一切正常使用，但如果用户离开应用程序一段时间然后回来，我会在下一个 NSOperation 运行时收到 EXC_BAD_ACCESS 错误。这似乎与用户是否将应用程序发送到后台无关紧要，而且似乎只有在上次数据连接建立后至少几分钟后才会发生。
我意识到这一定是某种形式的过度释放，但我的内存管理非常好，我看不出有什么问题。我的数据调用通常如下所示：
-(void)viewDidLoad {
[super viewDidLoad];
NSOperationQueue* tmpQueue = [[NSOperationQueue alloc] init];
self.queue = tmpQueue;
[tmpQueue release];
}
-(void)loadHistory {
GetHistoryOperation* operation = [[GetHistoryOperation alloc] init];
[operation addObserver:self forKeyPath:@"isFinished" options:0 context:NULL];
[self.queue addOperation:operation];
[operation release];
}
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
if ([keyPath isEqual:@"isFinished"] && [object isKindOfClass:[GetHistoryOperation class]]) {
GetHistoryOperation* operation = (GetHistoryOperation*)object;
if(operation.success) {
[self performSelectorOnMainThread:@selector(loadHistorySuceeded:) withObject:operation waitUntilDone:YES];
} else {
[self performSelectorOnMainThread:@selector(loadHistoryFailed:) withObject:operation waitUntilDone:YES];
}
} else {
[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
}
}
-(void)loadHistorySuceeded:(GetHistoryOperation*)operation {
if([operation.historyItems count] > 0) {
//display data here
} else {
//display no data alert
}
}
-(void)loadHistoryFailed:(GetHistoryOperation*)operation {
//show failure alert
}
而我的操作通常是这样的：
-(void)main {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSError* error = nil;
NSString* postData = [self postData];
NSDictionary *dictionary = [RequestHelper performPostRequest:kGetUserWalkHistoryUrl:postData:&error];
if(dictionary) {
NSNumber* isValid = [dictionary objectForKey:@"IsValid"];
if([isValid boolValue]) {
NSMutableArray* tmpDays = [[NSMutableArray alloc] init];
NSMutableDictionary* tmpWalksDictionary = [[NSMutableDictionary alloc] init];
NSDateFormatter* dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyyMMdd"];
NSArray* walksArray = [dictionary objectForKey:@"WalkHistories"];
for(NSDictionary* walkDictionary in walksArray) {
Walk* walk = [[Walk alloc] init];
walk.name = [walkDictionary objectForKey:@"WalkName"];
NSNumber* seconds = [walkDictionary objectForKey:@"TimeTaken"];
walk.seconds = [seconds longLongValue];
NSString* dateStart = [walkDictionary objectForKey:@"DateStart"];
NSString* dateEnd = [walkDictionary objectForKey:@"DateEnd"];
walk.startDate = [JSONHelper convertJSONDate:dateStart];
walk.endDate = [JSONHelper convertJSONDate:dateEnd];
NSString* dayKey = [dateFormatter stringFromDate:walk.startDate];
NSMutableArray* dayWalks = [tmpWalksDictionary objectForKey:dayKey];
if(!dayWalks) {
[tmpDays addObject:dayKey];
NSMutableArray* dayArray = [[NSMutableArray alloc] init];
[tmpWalksDictionary setObject:dayArray forKey:dayKey];
[dayArray release];
dayWalks = [tmpWalksDictionary objectForKey:dayKey];
}
[dayWalks addObject:walk];
[walk release];
}
for(NSString* dayKey in tmpDays) {
NSMutableArray* dayArray = [tmpWalksDictionary objectForKey:dayKey];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"startDate" ascending:YES];
NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
NSArray* sortedDayArray = [dayArray sortedArrayUsingDescriptors:sortDescriptors];
[sortDescriptor release];
[tmpWalksDictionary setObject:sortedDayArray forKey:dayKey];
}
NSSortDescriptor* sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:nil ascending:NO selector:@selector(localizedCompare:)];
self.days = [tmpDays sortedArrayUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]];
self.walks = [NSDictionary dictionaryWithDictionary:tmpWalksDictionary];
[tmpDays release];
[tmpWalksDictionary release];
[dateFormatter release];
self.success = YES;
} else {
self.success = NO;
self.errorString = [dictionary objectForKey:@"Error"];
}
if([dictionary objectForKey:@"Key"]) {
self.key = [dictionary objectForKey:@"Key"];
}
} else {
self.errorString = [error localizedDescription];
if(!self.errorString) {
self.errorString = @"Unknown Error";
}
self.success = NO;
}
[pool release];
}
-(NSString*)postData {
NSMutableString* postData = [[[NSMutableString alloc] init] autorelease];
[postData appendFormat:@"%@=%@", @"LoginKey", self.key];
return [NSString stringWithString:postData];
}
----
@implementation RequestHelper
+(NSDictionary*)performPostRequest:(NSString*)urlString:(NSString*)postData:(NSError**)error {
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
NSURL* url = [NSURL URLWithString:[NSString stringWithFormat:@"%@/%@", kHostName, urlString]];
NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:30];
[urlRequest setHTTPMethod:@"POST"];
if(postData && ![postData isEqualToString:@""]) {
NSString *postLength = [NSString stringWithFormat:@"%d", [postData length]];
[urlRequest setHTTPBody:[postData dataUsingEncoding:NSASCIIStringEncoding]];
[urlRequest setValue:postLength forHTTPHeaderField:@"Content-Length"];
[urlRequest setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
}
NSURLResponse *response = nil;
error = nil;
NSData *jsonData = [NSURLConnection sendSynchronousRequest:(NSURLRequest *)urlRequest returningResponse:(NSURLResponse **)&response error:(NSError **)&error];
NSString *jsonString = [[NSString alloc] initWithBytes: [jsonData bytes] length:[jsonData length] encoding:NSUTF8StringEncoding];
NSLog(@"JSON: %@",jsonString);
//parse JSON
NSDictionary *dictionary = nil;
if([jsonData length] > 0) {
dictionary = [[CJSONDeserializer deserializer] deserializeAsDictionary:jsonData error:error];
}
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
return dictionary;
}
如果我有自动释放池，崩溃发生在[pool release]。如果我不这样做，那么崩溃似乎只是出现在 main.m 方法中，而且我似乎没有得到任何有用的信息。每次测试之间我必须等待 10 分钟，这很难追踪！
如果有人能提供任何线索或方向，将不胜感激。
【问题讨论】：
-
释放内存前是否取消网络操作？
-
我不这么认为。我唯一一次这样做是在 viewWillDisappear 中，我循环遍历队列中的所有操作，如果
isExecuting为真，我将 viewController 作为isFinished键路径的观察者删除。
标签： iphone objective-c nsoperation