Objective-c Json解析空数组错误还是Bug？

Question

当我使用 tableview 解析 json 时，如果有 json 项目，但如果没有加载 json 项目，并且当我点击返回按钮时，一切都会好起来。

erminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'
*** First throw call stack:

我认为当我单击快速后退按钮并在我的表格视图代码下给出此错误时，json 不会加载。

    @interface MasterViewController ()

    @property (nonatomic, assign) NSInteger currentPage;
    @property (nonatomic, assign) NSInteger totalPages;
    @property (nonatomic, assign) NSInteger totalItems;
    @property (nonatomic, assign) NSInteger maxPages;

    @property (nonatomic, strong) NSMutableArray *activePhotos;
    @property (strong, nonatomic) NSMutableArray *staticDataSource;
    @property (nonatomic, strong) NSMutableArray *searchResults;

    @property (strong, nonatomic) IBOutlet UITableView *tableView;


    @end


            - (void)viewDidLoad
            {
                [super viewDidLoad];

                self.activePhotos = [[NSMutableArray alloc] init];
                self.searchResults = [[NSMutableArray alloc] init];
                self.staticDataSource = [[NSMutableArray alloc] init];


            }


            #pragma mark - Table View

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {

    return  self.activePhotos.count;
}



- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell;
    if (indexPath.row == [self.activePhotos count]) {
        cell = [self.tableView dequeueReusableCellWithIdentifier:@"LoadingCell" forIndexPath:indexPath];
        UIActivityIndicatorView *activityIndicator = (UIActivityIndicatorView *)[cell.contentView viewWithTag:100];
        [activityIndicator startAnimating];
    } else {
        NSDictionary *photoItem = self.activePhotos[indexPath.row];
        cell = [self.tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];

        cell.textLabel.text = [photoItem objectForKey:@"name"];
        if (![[photoItem objectForKey:@"description"] isEqual:[NSNull null]]) {
            cell.detailTextLabel.text = [photoItem objectForKey:@"description"];
        }


    }


    return cell;
}



- (void)loadPhotos:(NSInteger)page
{



    NSString *userismim =[[NSUserDefaults standardUserDefaults] stringForKey:@"userisim"];


    NSArray* words = [userismim componentsSeparatedByCharactersInSet :[NSCharacterSet whitespaceAndNewlineCharacterSet]];
    NSString* nospacestring = [words componentsJoinedByString:@""];


    NSLog(@"%@",nospacestring);


    NSString *apiURL = [NSString stringWithFormat:@"http://bla.com/server/table.php?user=%@",nospacestring];

    NSURLSession *session = [NSURLSession sharedSession];
    [[session dataTaskWithURL:[NSURL URLWithString:apiURL]
            completionHandler:^(NSData *data,
                                NSURLResponse *response,
                                NSError *error) {

                if (!error) {

                    NSError *jsonError = nil;
                    NSMutableDictionary *jsonObject = (NSMutableDictionary *)[NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&jsonError];

                    NSLog(@"%@",jsonObject);

                    [self.staticDataSource addObjectsFromArray:[jsonObject objectForKey:@"photos"]];

                    self.currentPage = [[jsonObject objectForKey:@"current_page"] integerValue];
                    self.totalPages  = [[jsonObject objectForKey:@"total_pages"] integerValue];
                    self.totalItems  = [[jsonObject objectForKey:@"total_items"] integerValue];

                    self.activePhotos = self.staticDataSource;

                    dispatch_async(dispatch_get_main_queue(), ^{
                        [self.tableView reloadData];
                    });
                }
            }] resume];
}

感谢一切。我需要你的帮助。

Answer 1

您正在显示活动指示器，该指示器将一直旋转直到加载 json。

如果您在json 加载之前按下返回按钮，则会发生应用程序尝试为数组分配空引用，这是不可能的，因此会引发错误。

为避免这种情况，您可以在请求发出后停止userInteraction，并仅在获得成功或失败响应后启用。

要禁用交互，请添加

[[UIApplication sharedApplicaton] beginIgnoringInteractionEvents]  

之后

NSURLSession *session = [NSURLSession sharedSession];

要再次启用，请添加：

 [[UIApplication sharedApplicaton] endIgnoringInteractionEvents]  

之前

if (!error) {

希望这能解决你的问题。