Question

我正在构建一个使用Parse作为Web后端的应用程序。我正在使用这段代码，但是当我运行它时它会告诉我：

*** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'

和

Warning: A long-running operation is being executed on the main thread.

我一直在研究，但我无法提出解决方案

我的代码：

部首：

#import <Parse/Parse.h>

@interface HomeViewController : PFQueryTableViewController <UITableViewDataSource, UITableViewDelegate>
@property (weak, nonatomic) IBOutlet UITableView *storiesTableView;

@end

实现：

#import "HomeViewController.h"

@interface HomeViewController () {
// Declare variables
NSArray *_stories;
int itemsCount;
BOOL firstOpen;
}

@end

@implementation HomeViewController

- (id)initWithCoder:(NSCoder *)aCoder
{
self = [super initWithCoder:aCoder];
if (self) {

    // The className to query on
    self.parseClassName = @"Story";

    // The key of the PFObject to display in the label of the default cell style
    self.textKey = @"objectId";

    // Whether the built-in pull-to-refresh is enabled
    self.pullToRefreshEnabled = YES;

    // Whether the built-in pagination is enabled
    self.paginationEnabled = NO;
}
return self;
}

- (PFQuery *)queryForTable
{
    PFQuery *query = [PFQuery queryWithClassName:self.parseClassName];

    itemsCount = [query countObjects];

    return query;
}

- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.

// Wise-verse.. but checks if this is the first open so that the user won
if (firstOpen == YES) {
    // Do nothing
} else {
    [self performSegueWithIdentifier:@"signInSegue" sender:self];
    firstOpen = YES;
}
}

-(void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:YES];
// Setup delegate and datasource
_storiesTableView.dataSource = self;
_storiesTableView.delegate = self;
}

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
// Return the number of sections.
return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
// Return the number of rows in the section.
return itemsCount;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath object:(PFObject *)object
{
static NSString *simpleTableIdentifier = @"cell";

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];
if (cell == nil) {
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleTableIdentifier];
}

// Configure the cell
UILabel *nameLabel = (UILabel*) [cell viewWithTag:10];
nameLabel.text = [object objectForKey:@"objectId"];

UILabel *descriptionLabel = (UILabel*) [cell viewWithTag:20];
descriptionLabel.text = [object objectForKey:@"Story"];

return cell;
}

-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
// Segue over to the viewing page
[self performSegueWithIdentifier:@"detailSegue" sender:self];
}

@end

我的解析由这些列组成，当前只有一行包含这些数据：

objectId：UYpXIiQbPQ
createdAt：2014-09-26T17：00：28.079Z
updatedAt：2014-09-26T17：01：19.128Z
ACL :(未定义）
故事：“我在星期一早上7点钟醒来。狗在吠叫，天空开着”（只是一个完全随机的测试）
作者：Erik
评论（数组）:(未定义）
类别（字符串）：测试类别

有人可以帮忙吗？

---- ---- EDIT 堆栈跟踪：

    (lldb) bt
* thread #1: tid = 0xe3b1, 0x00000001947ac0a8 libobjc.A.dylib`objc_exception_throw, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
    frame #0: 0x00000001947ac0a8 libobjc.A.dylib`objc_exception_throw
    frame #1: 0x00000001840abbec CoreFoundation`-[__NSArrayM objectAtIndex:] + 264
  * frame #2: 0x000000010012efdc iStory`-[PFQueryTableViewController tableView:cellForRowAtIndexPath:](self=0x000000014c613dc0, _cmd=<unavailable>, otherTableView=<unavailable>, indexPath=<unavailable>) + 196 at PFQueryTableViewController.m:307
    frame #3: 0x0000000188c3e39c UIKit`-[UITableView _createPreparedCellForGlobalRow:withIndexPath:willDisplay:] + 544
    frame #4: 0x0000000188c32fc4 UIKit`-[UITableView _updateVisibleCellsNow:isRecursive:] + 2360
    frame #5: 0x0000000188a28c60 UIKit`-[UITableView layoutSubviews] + 172
    frame #6: 0x0000000188945874 UIKit`-[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 572
    frame #7: 0x000000018829dd58 QuartzCore`-[CALayer layoutSublayers] + 168
    frame #8: 0x0000000188298944 QuartzCore`CA::Layer::layout_if_needed(CA::Transaction*) + 320
    frame #9: 0x00000001882987e8 QuartzCore`CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 32
    frame #10: 0x0000000188297fe8 QuartzCore`CA::Context::commit_transaction(CA::Transaction*) + 276
    frame #11: 0x0000000188297d6c QuartzCore`CA::Transaction::commit() + 436
    frame #12: 0x000000018893c848 UIKit`_afterCACommitHandler + 156
    frame #13: 0x000000018417e388 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 32
    frame #14: 0x000000018417b314 CoreFoundation`__CFRunLoopDoObservers + 360
    frame #15: 0x000000018417b6f4 CoreFoundation`__CFRunLoopRun + 836
    frame #16: 0x00000001840a9664 CoreFoundation`CFRunLoopRunSpecific + 396
    frame #17: 0x000000018d1eb5a4 GraphicsServices`GSEventRunModal + 168
    frame #18: 0x00000001889ae4f8 UIKit`UIApplicationMain + 1488
    frame #19: 0x00000001000f541c iStory`main(argc=1, argv=0x000000016fd13a60) + 116 at main.m:14
    frame #20: 0x0000000194e1aa08 libdyld.dylib`start + 4

非常感谢！此致埃里克

Answer 1

Warning: A long-running operation is being executed on the main thread

可能是在没有完成块的情况下运行PFQuery的结果。 Parse提供了一些选项，例如countObjectsInBackground。

Answer 2

*由于未捕获的异常终止应用＆＃39; NSRangeException＆＃39;，原因：＆＃39; * - [__ NSArrayM objectAtIndex：]：索引0超出范围空数组＆＃39;

您的第一个错误表明您正在尝试从空数组中获取值。这可能是因为此时您仍然没有任何价值可供使用，因为它尚未完全从Parse下载并且可用。尝试NSLog itensCount以及queryForTable方法中的Parse对象键值，以检查在使用之前是否接收到任何值，然后在tableView上。

警告：正在执行长时间运行的操作线程。

这是因为您正在进行同步网络连接，这可能会冻结应用程序屏幕，但有时也会使其崩溃。你应该总是进行异步网络连接（使用后台线程块），而Parse有自己的方法，比如findObjectsInBackgroundWithBlock（用于查询）。然后，您可以在实际接收数据后立即提供tableView。查看解析文档以获取更多信息。 https://www.parse.com/docs/ios_guide#queries/iOS 像这样：

[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {

// if received successfully 
if (!error) {

// you have properly received objects so update your tableView with received data


}

else
{

// Log details of the failure
NSLog(@"Parse Error: %@ %@", error, [error userInfo]);

}
}

希望它有所帮助。

Answer 3

你在研究中尝试过这些吗？

https://www.parse.com/questions/warning-a-long-running-parse-operation-is-being-executed-on-the-main-thread-break-on-warnparseoperationonmainthread-to-debug--2

https://www.parse.com/questions/a-long-running-parse-operation-is-being-executed-on-the-main-thread

A long-running Parse operation is being executed on the main thread

https://teamtreehouse.com/forum/how-to-get-pfuser-if-i-only-have-users-objectid

https://github.com/BoltsFramework/Bolts-iOS/blob/master/Bolts/Common/BFTask.m

您似乎没有在后台线程块中获取对象

[query getObjectInBackgroundWithId:userId block:^(PFObject *object, NSError *error) {

//Implimentation

 }];

IOS中的后台线程与Parse

3 个答案: