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标题: ios - 使用 Blocks 的后台 performFetchWithCompletionHandler 导致崩溃 [打印本页]

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作者: 菜鸟教程小白    时间: 2022-12-13 10:51
标题: ios - 使用 Blocks 的后台 performFetchWithCompletionHandler 导致崩溃

我有一个应用程序可以成功获取并显示我想添加后台获取的 RSS 提要。我收到:线程 1 EXC_BAD_ACCESS(代码=1，地址=0x10)，如下所示。

在应用委托(delegate)中:

- (BOOL)applicationUIApplication *)application didFinishLaunchingWithOptionsNSDictionary *)launchOptions {
    //setup background fetch
[application setMinimumBackgroundFetchInterval: UIApplicationBackgroundFetchIntervalMinimum];

return YES;

}

        //background fetch new RSS Feeds
-(void)applicationUIApplication *)application performFetchWithCompletionHandlervoid (^)(UIBackgroundFetchResult))completionHandler
{
    NSLog(@"performFetchWithCompletionHandler");
    UIStoryboard *mainStoryboard = [UIStoryboard storyboardWithName"Main" bundle:nil];
    MasterViewController *navigationController = [mainStoryboard instantiateViewControllerWithIdentifier"MasterView"];
    MasterViewController *viewController = navigationController;

    [viewController fetchNewDataWithCompletionHandler:^(UIBackgroundFetchResult result) {
        completionHandler(result);
    }];
}

在我的主视图 Controller 中:

@property (nonatomic, copy) void (^completionHandler)(BOOL);
- (void) fetchNewDataWithCompletionHandler: (void (^)(UIBackgroundFetchResult))completionHandler;
- (void) startParsingWithCompletionHandlervoid (^)(BOOL))completionHandler;

-(void)fetchNewDataWithCompletionHandlervoid (^)(UIBackgroundFetchResult))completionHandler{

self.completionHandler = UIBackgroundFetchResultNewData; //completionHandler;
[self startParsingWithCompletionHandler:^(BOOL success){

    if (success) {
        completionHandler(UIBackgroundFetchResultNewData);
        NSLog(@"completionHandler");
    }
    else{
        NSLog(@"error");
    }
}];

}

    - (void) storyIsDone//called when parser completed one rss feed
{
    numberOfCompletedStories ++;
    if (numberOfCompletedStories == self.rssFeedAddresses.count)
    {
            //if all the feeds are done cancel time-out timer
        [NSObject cancelPreviousPerformRequestsWithTarget: self selector: @selector(stopParsing) object: nil];
        [self.activityIndicator stopAnimating];
        storysAreLoading = NO;
        [self.refreshControl endRefreshing];
        [[NSNotificationCenter defaultCenter] addObserver: self selector: @selector(reloadRSSfeeds) name: @"ReloadFeeds" object: nil];
        canRefresh = YES;
        NSLog(@"call back");
        self.completionHandler (YES);//crash here:  Thread 1 EXC_BAD_ACCESS (code=1, Address=0x10)
    }//else not yet complete
}

我收到的输出是:

执行FetchWithCompletionHandler

回电

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Best Answer-推荐答案

self.completionHandler = UIBackgroundFetchResultNewData; 

不匹配类型。 completionHandler 属于 (void (^)(UIBackgroundFetchResult)) 类型，而 UIBackgroundFetchResultNewData 属于 NSUInteger 类型。

typedef enum : NSUInteger {
   UIBackgroundFetchResultNewData,
   UIBackgroundFetchResultNoData,
   UIBackgroundFetchResultFailed 
} UIBackgroundFetchResult;

所以当你调用self.completionHandler(YES)时，self.completionHandler是一个NSUInteger，所以NSUInteger(YES) 没有多大意义。

关于ios - 使用 Blocks 的后台 performFetchWithCompletionHandler 导致崩溃，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/30402990/

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