Question

我正在使用NSOperation队列来获取图像并在我的tableview单元格中显示它们。在图像返回之前，我会显示加载叠加层，一旦操作完成，它就会暗示委托，然后我删除加载叠加层。

现在，我想在说出5秒之后超时获取操作并删除加载覆盖，但是基于计时器的方法没有用完。请建议。

以下是我的代码：

#import "MyImageFetchOperation.h"
#import "MyImageFetchController.h"
#import "MyHTTPRequest.h"

@interface MyImageFetchOperation ()

@property (nonatomic, strong) NSString *imageURL;
@property (nonatomic, weak) id <MyOperationCompletedDelegate> delegate;
@property (nonatomic, assign) BOOL isCompleted;
@property (nonatomic, weak) NSTimer *timeoutTimer;

@end

@implementation MyImageFetchOperation
@synthesize imageURL;
@synthesize delegate;
@synthesize isCompleted;

#define kMyImageFetchTimeout 5

#pragma mark -
#pragma mark Destruction

- (void)dealloc {
    self.delegate = nil;
}


- (id)initWithImageURL:(NSString *)iImageURL delegate:(id)iDelegate {
    if (self = [super init]) {
        self.imageURL = iImageURL;
        self.delegate = iDelegate;
    }
    return self;
}


- (void)main {
    self.isCompleted = NO;
    NSMutableURLRequest *aRequest = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:self.imageURL]];
    [aRequest setTimeoutInterval:kMyImageFetchTimeout];
    [aRequest setHTTPMethod:@"GET"];

    self.timeoutTimer = [NSTimer scheduledTimerWithTimeInterval:kMyImageFetchTimeout target:self selector:@selector(requestTimedOut) userInfo:nil repeats:NO];

    [NSURLConnection sendAsynchronousRequest:aRequest queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *iData, NSError *iConnectionError) {
        if (!self.isCompleted) {
            if (iConnectionError) {
                [[MyImageFetchController sharedRunnerImageFetchControllerMy] urlFailed:self.imageURL];
            }

            UIImage *anImage = [UIImage imageWithData:iData];

            if (anImage) {
                [MyUtilities cacheFile:anImage withName:[self.imageURL runnerMD5HashMy] toDirectory:[self.delegate cacheDirectoryForImages]];
            } else {
                [[MyImageFetchController sharedRunnerImageFetchControllerMy] urlFailed:self.imageURL];
            }

            [self.delegate operationCompletedForURL:self.imageURL];
            self.isCompleted = YES;
        }
    }];
}


- (void)requestTimedOut {
    self.isCompleted = YES;
    [self.timeoutTimer invalidate];
    self.timeoutTimer = nil;
    [[MyImageFetchController sharedRunnerImageFetchControllerMy] urlFailed:self.imageURL];
    [self.delegate operationCompletedForURL:self.imageURL];
}

@end

Answer 1

为什么不打电话

[self.delegate operationCompletedForURL:self.imageURL];

在这个if？

里面

if (iConnectionError) {

另一方面，你不应该在该块中使用self，你应该使用__block变量。

Answer 2

你需要一个运行循环来使你的计时器工作，如下所示：

- (void)main
{
    // your code
    yourTimer = ... // create your timer

    NSRunLoop* runLoop = [NSRunLoop currentRunLoop];
    [runLoop addTimer:yourTimer forMode:NSRunLoopCommonModes];
    [runLoop run];
}

哦，我想最好在main中设置你自己的自动释放池。

在NSOperationQueue中定时同步服务器调用

2 个答案: