+ entityForName：nil不是合法的NSManagedObjectContext参数搜索实体名称'IndianGroceries'

Question

我收到一个错误，当我试图将我的数据从核心数据加载到表视图控制器。我根据论坛上的讨论修正了代码，但仍然出现错误。

SearchViewController

@interface SearchViewController() 

- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath; 
@end 

@implementation SearchViewController 
@synthesize managedObjectContext; 
@synthesize fetchedResultsController = _fetchedResultsController; 
@synthesize searchBar,tView; 
@synthesize noResultsLabel; 

-(id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
{ 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; 
    if (self) { 
     // Custom initialization 
    } 
    return self; 
} 

-(void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    self.searchBar.delegate = self; 
    self.tView.delegate = self; 
    self.tView.dataSource = self; 

    noResultsLabel = [[UILabel alloc] initWithFrame:CGRectMake(20, 90, 200, 30)]; 
    [self.view addSubview:noResultsLabel]; 
    noResultsLabel.text = @"No Results"; 
    [noResultsLabel setHidden:YES]; 

    // Do any additional setup after loading the view. 
} 

-(void) viewWillAppear:(BOOL)animated 
{ 
    [super viewWillAppear:animated]; 
    [self.searchBar becomeFirstResponder]; 

} 

#pragma mark - Search bar delegate 

-(void)searchBarSearchButtonClicked:(UISearchBar *)searchBar 
{ 

    NSError *error; 

    if (![[self fetchedResultsController] performFetch:&error]) 
{ 

     NSLog(@"Error in search %@, %@", error, [error userInfo]); 

    } else 
{ 

     [self.tView reloadData]; 
     [self.searchBar resignFirstResponder]; 

     [noResultsLabel setHidden:_fetchedResultsController.fetchedObjects.count > 0]; 

    } 
} 

#pragma mark - Table view data source 

-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView 
{ 
    return 1; 
} 

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section 
{ 
    id sectionInfo = 
    [[_fetchedResultsController sections] objectAtIndex:section]; 
    return [sectionInfo numberOfObjects]; 

} 

-(void)configureCell:(TableCell *)cell atIndexPath:(NSIndexPath *)indexPath { 
    IndianGroceries *info = [_fetchedResultsController objectAtIndexPath:indexPath]; 
    cell.lblCountry.text = info.country; 
    cell.lblCityName.text = info.cityName; 
    cell.lblEmailId.text = info.emailId; 
    cell.lblFirstName.text = info.firstName; 
    cell.lblLastName.text = info.lastName; 
    cell.lblPhoneNumber.text = info.phoneNumber; 
    cell.lblStreetName.text = info.streetName1; 
    cell.lblStreetName2.text = info.streetName2; 
    cell.lblZipCode.text = info.zipCode; 
} 

    -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{ 
    static NSString *CellIdentifier = @"Cell"; 
    TableCell *cell = (TableCell *)[self.tView dequeueReusableCellWithIdentifier:CellIdentifier]; 
    if (cell == nil) 
    { 
     cell=[[TableCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier]; 
    } 

    [self configureCell:cell atIndexPath:indexPath]; 

    return cell; 
} 


#pragma mark - fetchedResultsController 

// Change this value to experiment with different predicates 
#define SEARCH_TYPE 0 


-(NSFetchedResultsController *)fetchedResultsController 
{ 
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; 
    NSEntityDescription *entity = [NSEntityDescription 
       insertNewObjectForEntityForName:@"IndianGroceries" inManagedObjectContext:[self managedObjectContext]]; 
    [fetchRequest setEntity:entity]; 

    NSSortDescriptor *sort = [[NSSortDescriptor alloc] 
           initWithKey:@"country" ascending:NO]; 
    [fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]]; 
    [fetchRequest setFetchBatchSize:20]; 

    NSArray *queryArray; 

    if ([self.searchBar.text rangeOfString:@":"].location != NSNotFound) 
    { 
     queryArray = [self.searchBar.text componentsSeparatedByString:@":"]; 
    } 

    NSLog(@"search is %@", self.searchBar.text); 

    NSPredicate *pred; 

    switch (SEARCH_TYPE) { 

     case 0: // name contains, case sensitive 
      pred = [NSPredicate predicateWithFormat:@"name CONTAINS %@", self.searchBar.text]; 
      break; 
     default: 
      break; 
    } 

    [fetchRequest setPredicate:pred]; 

    NSFetchedResultsController *theFetchedResultsController = 
    [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest 
             managedObjectContext:[self managedObjectContext]sectionNameKeyPath:nil 
                cacheName:nil]; // better to not use cache 
    self.fetchedResultsController = theFetchedResultsController; 
    _fetchedResultsController.delegate = self; 

    return _fetchedResultsController; 

} 

DataViewController

@interface DataViewController() 
@property(strong,nonatomic) NSArray *SearchResultContries; 
//- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath; 

@end 

@implementation DataViewController 
@synthesize contacts; 
@synthesize managedObjectContext; 
@synthesize fetchedResultsController = _fetchedResultsController; 

-(NSManagedObjectContext *)managedObjectContext 
{ 
    NSManagedObjectContext *context = nil; 
    id delegate = [[UIApplication sharedApplication]delegate]; 

    if ([delegate performSelector:@selector(managedObjectContext)]) 
    { 
     context = [delegate managedObjectContext]; 
    } 
    return context; 
} 

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
{ 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; 
    if (self) { 
     // Custom initialization 
    } 
    return self; 
} 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    [self.navigationController setNavigationBarHidden:NO animated:YES]; 

    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemSearch target:self action:@selector(showSearch)]; 
    // Do any additional setup after loading the view. 
} 

-(void)viewDidAppear:(BOOL)animated{ 

    //here we get the car from the president data store (or) the database 
    NSManagedObjectContext *moc = [self managedObjectContext]; 
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc]initWithEntityName:@"IndianGroceries"]; 
    contacts = [[moc executeFetchRequest:fetchRequest error:nil]mutableCopy]; 
    [self.tableView reloadData]; 

} 

-(void)viewWillAppear:(BOOL)animated 
{ 
    [self.tableView reloadData]; 
} 

- (void) showSearch { 

    SearchViewController *searchViewController = [[SearchViewController alloc] init]; 
    searchViewController.managedObjectContext = self.managedObjectContext; 
    UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle: nil]; 
    searchViewController = [storyboard instantiateViewControllerWithIdentifier:@"searchView"]; 
    [self.navigationController pushViewController:searchViewController animated:YES]; 

} 

- (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 contacts.count; 
} 
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{ 
    static NSString *CellIdentifier = @"CellID"; 
    TableCell *cell = (TableCell *)[self.tableView dequeueReusableCellWithIdentifier:CellIdentifier]; 
    if (cell == nil) 
    { 
     cell=[[TableCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier]; 
    } 

    NSManagedObject *con = [contacts objectAtIndex:indexPath.row]; 
    [cell.lblEmailId setText:[NSString stringWithFormat:@"%@",[con valueForKey:@"emailId"]]]; 
    [cell.lblFirstName setText:[NSString stringWithFormat:@"%@",[con valueForKey:@"firstName"]]]; 
    [cell.lblLastName setText:[NSString stringWithFormat:@"%@",[con valueForKey:@"lastName"]]]; 
    [cell.lblStreetName setText:[NSString stringWithFormat:@"%@",[con valueForKey:@"streetName1"]]]; 
    [cell.lblStreetName2 setText:[NSString stringWithFormat:@"%@",[con valueForKey:@"streetName2"]]]; 
    [cell.lblCityName setText:[NSString stringWithFormat:@"%@",[con valueForKey:@"cityName"]]]; 
    [cell.lblZipCode setText:[NSString stringWithFormat:@"%@",[con valueForKey:@"zipCode"]]]; 
    [cell.lblPhoneNumber setText:[NSString stringWithFormat:@"%@",[con valueForKey:@"phoneNumber"]]]; 
    [cell.lblCountry setText:[NSString stringWithFormat:@"%@",[con valueForKey:@"country"]]]; 

    return cell; 
} 

Answer 1

的NSManagedObjectContext要传递到entityForName:inManagedObjectContext:为零。该方法需要一个有效的NSManagedObjectContext实例。

看到这个答案： '+entityForName: nil is not a legal NSManagedObjectContext parameter - Core Data