当我尝试将数据从Core Data加载到Table View控制器时，出现错误。我根据论坛中的讨论更正了代码，但仍然收到错误。
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;
}
答案 0 :(得分：-1)
您传递给NSManagedObjectContext的{{1}}为零。该方法需要有效的NSManagedObjectContext实例。
看到这个答案： '+entityForName: nil is not a legal NSManagedObjectContext parameter - Core Data