objective-c - 使用异步 NSURLConnection 获取本地文件是否过度？

Question

我想从磁盘读取本地 JSON 文件(大约 5,000 多个记录/对象)，并且我有此代码并正在尝试使用 Realm

我想在完成加载和解析后更新我的用户界面；我已经尝试了一些变体，但我现在拥有的这个变体似乎有点矫枉过正。

NSURL *url = [[NSBundle mainBundle] URLForResource:fightersFilename withExtension:fightersFileExtension];
NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:30.0];

NSOperationQueue *queue = [[NSOperationQueue alloc] init];

[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
    if (!error && data) {
         //call a delegate to send the data to your page from where it was called

        dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

        dispatch_async(queue, ^{
            NSError *error=nil;
            NSMutableArray *result = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&error];

            dispatch_async(dispatch_get_main_queue(), ^{
                if (!error) {
                    // Get realm and table instances for this thread
                    RLMRealm *realm = [RLMRealm defaultRealm]; // Create realm pointing to default file

                    [realm beginWriteTransaction];

                    for (NSDictionary *fighterDict in result) {

                        DDLogVerbose(@"%@ %@", fighterDict[@"name"], fighterDict[@"filename"]);

                        Fighter *f = [[Fighter alloc] init];
                        f.name = fighterDict[@"name"];
                        f.filename = fighterDict[@"filename"];

                        [realm addObject:f];
                    }

                    // Commit the write transaction
                    // to make this data available to other threads
                    [realm commitWriteTransaction];

                    DDLogVerbose(@"%d fighters in realm",         [[Fighter allObjects] count]);
                }
            });
        });

    } else {
         //show alert that an error has occurred during downloading data from net.
        NSLog(@"JSON read error: %@", error);
    }
 }];

queue=nil;

我的想法是，我想读取 JSON 文件，解析它并将其放入对象中，然后一旦完成，更新我的 UI 或 UX。

鉴于此，上述是一个好的解决方案吗？

Answer 1

你太努力了。

在后台队列的异步调度 block 中，读取文件并同步解析它。完成后，在主队列上触发 after 函数。我将很快编辑它以添加特定代码。

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    NSURL *url = [[NSBundle mainBundle] URLForResource:fightersFilename     
                                         withExtension:fightersFileExtension];
    NSAssert(url!=nil, @"URL not found for target resource.");
    NSData *data = [NSData dataWithContentsOfURL:url];
    NSAssert(data!=nil, @"Reading data file failed.");
    NSError *parseError = nil;
    NSMutableArray *result = [NSJSONSerialization JSONObjectWithData:data 
                                                             options:NSJSONReadingMutableContainers 
                                                               error:&parseError];
    //TODO: Handle this sanely
    NSAssert(parseError==nil, @"Parsing JSON object failed."); 
    dispatch_async(dispatch_get_main_queue(), ^{
        [self didFinishLoadingResource:result];
    });
});