Question

我目前正在使用CoreData并尝试使用NSFetchedResultsController获取数据。但该应用程序在以下行崩溃

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


#the app crashes here
id sectionInfo = [[self.fetchedRequestController sections]objectAtIndex:section];


    return [sectionInfo numberOfObjects];

}

错误消息： - [__ NSArrayM objectAtIndex：]：索引9超出空数组的界限。

在你告诉我数组为空之前，我知道但是如果填充它怎么办？我不知道我哪里出错，其他问题都无法提供帮助。

AppDelgate.m 只是从核心数据预设中复制和粘贴。以防万一：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

return YES;
}

- (void)applicationWillResignActive:(UIApplication *)application {
// Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
// Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}

- (void)applicationDidEnterBackground:(UIApplication *)application {
// Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
// If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}

- (void)applicationWillEnterForeground:(UIApplication *)application {
// Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}

- (void)applicationDidBecomeActive:(UIApplication *)application {
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

- (void)applicationWillTerminate:(UIApplication *)application {
// Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
// Saves changes in the application's managed object context before the application terminates.
[self saveContext];
}

#pragma mark - Core Data stack


- (NSURL *)applicationDocumentsDirectory {
// The directory the application uses to store the Core Data store file. This code uses a directory named "controwl.a" in the application's documents directory.
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}

- (NSManagedObjectModel *)managedObjectModel {
// The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.
if (_managedObjectModel != nil) {
    return _managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"trackingData" withExtension:@"momd"];
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return _managedObjectModel;
}

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
// The persistent store coordinator for the application. This implementation creates and return a coordinator, having added the store for the application to it.
if (_persistentStoreCoordinator != nil) {
    return _persistentStoreCoordinator;
}

// Create the coordinator and store

_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"timetracking.sqlite"];
NSError *error = nil;
NSString *failureReason = @"There was an error creating or loading the application's saved data.";
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
    // Report any error we got.
    NSMutableDictionary *dict = [NSMutableDictionary dictionary];
    dict[NSLocalizedDescriptionKey] = @"Failed to initialize the application's saved data";
    dict[NSLocalizedFailureReasonErrorKey] = failureReason;
    dict[NSUnderlyingErrorKey] = error;
    error = [NSError errorWithDomain:@"YOUR_ERROR_DOMAIN" code:9999 userInfo:dict];
    // Replace this with code to handle the error appropriately.
    // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();
}

return _persistentStoreCoordinator;
}


- (NSManagedObjectContext *)managedObjectContext {
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.)
if (_managedObjectContext != nil) {
    return _managedObjectContext;
}

NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (!coordinator) {
    return nil;
}
_managedObjectContext = [[NSManagedObjectContext alloc] init];
[_managedObjectContext setPersistentStoreCoordinator:coordinator];
return _managedObjectContext;
}

#pragma mark - Core Data Saving support

- (void)saveContext {
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil) {
    NSError *error = nil;
    if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
        // Replace this implementation with code to handle the error appropriately.
        // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }
}
}

@end

调用 fetchedResultsController 的TableViewClass。

#import "FirstTableViewController.h"

@interface FirstTableViewController ()

@end

@implementation FirstTableViewController
@synthesize fetchedRequestController = _fetchedRequestController;
@synthesize managedObjectContext = _managedObjectContext;

- (void)viewDidLoad {
[super viewDidLoad];

NSError *error;
if (![[self fetchedRequestController]performFetch:&error]) {
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    exit(-1);
}

self.title = @"Customer Names";


_managedObjectContext = [(AppDelegate*)[[UIApplication sharedApplication]delegate] managedObjectContext];



NSManagedObject* customer;

customer = [NSEntityDescription insertNewObjectForEntityForName:@"Customer" inManagedObjectContext:_managedObjectContext];



}

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

- (NSFetchedResultsController *)fetchedRequestController {
if (_fetchedRequestController != nil) {
    return _fetchedRequestController;
}

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc]init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Customer" inManagedObjectContext:_managedObjectContext];
[fetchRequest setEntity:entity];

NSSortDescriptor *sort = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:NO];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];

[fetchRequest setFetchBatchSize:20];

NSFetchedResultsController *theFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:_managedObjectContext sectionNameKeyPath:@"nam" cacheName:@"Root"];


self.fetchedRequestController = theFetchedResultsController;
_fetchedRequestController.delegate = self;


return _fetchedRequestController;

}

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

    id sectionInfo = [[self.fetchedRequestController sections]objectAtIndex:section];
    return [sectionInfo numberOfObjects];

}

- (void)configureCell:(UITableViewCell*)cell  atIndexPath:(NSIndexPath *)indexPath {
UIViewController *customer = [_fetchedRequestController objectAtIndexPath:indexPath];
cell.textLabel.text = @"test";
}
#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
#warning Potentially incomplete method implementation.
// Return the number of sections.
return 10;
}


- (void)viewDidUnload {
    self.fetchedRequestController = nil;
}
@end

Answer 1

您numberOfSectionsInTableView:的实施表明有10个部分。你的崩溃告诉你的是这不是真的。表视图询问委托应该有多少部分，然后询问每个部分的详细信息。如果返回错误数量的节，则表视图会询问有关不存在节的详细信息。

您不应该对部分数量进行硬编码。 NSFetchedResultsController的文档提供了一个示例实现，可能就是您所需要的：

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return [self.fetchedRequestController sections] count];
}

- [__ NSArrayM objectAtIndex：]：索引9超出空数组的边界'

1 个答案: