尝试segue时让NSArray出现空崩溃

Question

我不理解这个查询我做的和我尝试执行以执行segue的按钮之间的相互关系。

以下是查询

- (void) queryData {


    float navBarHeight = self.navigationController.navigationBar.frame.size.height;

    float statusHeight = [[UIApplication sharedApplication] statusBarFrame].size.height;

    float tabBarHeight = self.tabBarController.tabBar.frame.size.height;

    CGSize screenSize = [[UIScreen mainScreen] bounds].size;


    PFObject *queryPhotos = self.sellerObject;
    PFQuery *query = [PFQuery queryWithClassName:@"Photo"];

    if (self.categoryChosenBool == NO) {
        [query whereKey:@"userTookPhoto" equalTo:queryPhotos];
        [query includeKey:@"userTookPhoto"];
        [query orderByDescending:@"createdAt"];

    }
    else if (self.categoryChosenBool == YES)
    {
        [query whereKey:@"userTookPhoto" equalTo:queryPhotos];
        [query includeKey:@"userTookPhoto"];
        [query whereKey:@"category" containsString:self.chosenCategoryText];
        [query orderByDescending:@"createdAt"];
    }

    [query findObjectsInBackgroundWithBlock:^(NSArray * _Nullable objects, NSError * _Nullable error)
    {
    if (!error) {
        imageFilesArray = [[NSArray alloc] initWithArray:objects];

                    if ((imageFilesArray.count % 3)) {
                        CGFloat height = imageFilesArray.count / 3;

                        CGFloat roundedUp = ceilf(height + 1);

                        NSLog(@"1 %f",roundedUp + 1);


                        if (screenSize.height < 569) {
                            NSLog(@"iphone 5 or 4");
                            CGFloat cellHeight = roundedUp * 106.5;


                            [_productCollectionView setFrame:CGRectMake(0, _filterButton.frame.origin.y + _filterButton.frame.size.height + 15, self.view.frame.size.width, cellHeight)];

                            [_contentView setFrame:CGRectMake(0, 0, self.view.frame.size.width, cellHeight + _productCollectionView.frame.origin.y)];
                            [_scrollView setContentSize:CGSizeMake(self.view.frame.size.width, cellHeight + _productCollectionView.frame.origin.y + statusHeight + navBarHeight + tabBarHeight)];


                        }
                        else if (screenSize.height > 666){
                            NSLog(@"iphone 6 or 6Plus");
                            CGFloat cellHeight = roundedUp * 125;

                            [_productCollectionView setFrame:CGRectMake(0, _filterButton.frame.origin.y + _filterButton.frame.size.height + 15, self.view.frame.size.width, cellHeight)];

                            [_contentView setFrame:CGRectMake(0, 0, self.view.frame.size.width, cellHeight + _productCollectionView.frame.origin.y)];
                            [_scrollView setContentSize:CGSizeMake(self.view.frame.size.width, cellHeight + _productCollectionView.frame.origin.y + statusHeight + navBarHeight + tabBarHeight)];


                        }


                    }else{
                        CGFloat height = imageFilesArray.count / 3;

                        CGFloat roundedUp = ceilf(height);

                        NSLog(@"2 %f",roundedUp);


                        if (screenSize.height < 569) {
                            NSLog(@"iphone 5 or 4");
                            CGFloat cellHeight = roundedUp * 106.5;

                            if (objects.count < 1) {
                                [_productCollectionView setFrame:CGRectMake(0, _filterButton.frame.origin.y + _filterButton.frame.size.height + 15, self.view.frame.size.width, self.view.frame.size.height - tabBarHeight - statusHeight - navBarHeight - _filterButton.frame.origin.y - _filterButton.frame.size.height )];
                            }
                            else{

                            [_productCollectionView setFrame:CGRectMake(0, _filterButton.frame.origin.y + _filterButton.frame.size.height + 15, self.view.frame.size.width, cellHeight)];

                            [_contentView setFrame:CGRectMake(0, 0, self.view.frame.size.width, cellHeight + _productCollectionView.frame.origin.y)];
                            [_scrollView setContentSize:CGSizeMake(self.view.frame.size.width, cellHeight + _productCollectionView.frame.origin.y + statusHeight + navBarHeight + tabBarHeight)];
                            }

                        }
                        else if (screenSize.height > 666){
                            NSLog(@"iphone 6 or 6Plus");
                            CGFloat cellHeight = roundedUp * 125;

                            if (objects.count < 1) {
                                [_productCollectionView setFrame:CGRectMake(0, _filterButton.frame.origin.y + _filterButton.frame.size.height + 15, self.view.frame.size.width, self.view.frame.size.height - tabBarHeight - statusHeight - navBarHeight - _filterButton.frame.origin.y - _filterButton.frame.size.height )];
                            }
                            else{

                                [_productCollectionView setFrame:CGRectMake(0, _filterButton.frame.origin.y + _filterButton.frame.size.height + 15, self.view.frame.size.width, cellHeight)];

                                [_contentView setFrame:CGRectMake(0, 0, self.view.frame.size.width, cellHeight + _productCollectionView.frame.origin.y)];
                                [_scrollView setContentSize:CGSizeMake(self.view.frame.size.width, cellHeight + _productCollectionView.frame.origin.y + statusHeight + navBarHeight + tabBarHeight)];
                            }


                        }

                    }

         [SVProgressHUD dismiss];
        [_productCollectionView reloadData];
        [self.refreshControl endRefreshing];

    }

    }];

}

该按钮由以下人员执行：

-(void)executeSegue
{
  [self performSegueWithIdentifier:@"nextView" sender:self];

}

在这种情况下，查询为空，但我不明白为什么该方法因此而崩溃。

但是当我注释掉Query时，它完全可以执行segue。

Answer 1

你不能在后台线程中调用它：

[SVProgressHUD dismiss];
[_productCollectionView reloadData];
[self.refreshControl endRefreshing];

在主线程中使用它。尝试使用此

dispatch_async(dispatch_get_main_queue(), ^{
   [SVProgressHUD dismiss];
   [_productCollectionView reloadData];
   [self.refreshControl endRefreshing];
});