Question

虽然我对核心数据进行了多次训练，但是当我按下导航栏中的添加按钮时，它会推送一个新的ViewController，我可以插入数据来创建一个新的Object。按我保存后导航栏弹出viewController，我再次看到我的表。

大多数情况下，表格不会显示该元素，但是如果我点击该行显示该元素的名称，它就像表格需要重新加载一样，因为元素在那里但它没有显示。

为什么会这样？这是我的Apllication的代码：我复制了所有课程，但我相信你可以跳过appdelegate和masterviewcontroller。

AppDelegate.h

#import <UIKit/UIKit.h>
@interface AppDelegate : UIResponder <UIApplicationDelegate>
@property (strong, nonatomic) UIWindow *window;
@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;

- (void)saveContext;
- (NSURL *)applicationDocumentsDirectory;

@end

AppDelegate.m

#import "AppDelegate.h"
#import "MasterViewController.h"
#import "IngredientsTableViewController.h"

@implementation AppDelegate

@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.

    MasterViewController *masterVC = [[MasterViewController alloc]initWithNibName:@"MasterViewCOntroller" bundle:nil];
    //masterVC.managedObjectContex = self.managedObjectContext;

    IngredientsTableViewController *ingredientsTVC = [[IngredientsTableViewController alloc]initWithNibName:@"IngredientsTableViewController" bundle:nil];
    ingredientsTVC.managedObjectContext = self.managedObjectContext;

    UINavigationController *navigationControllerIngredients = [[UINavigationController alloc]initWithRootViewController:ingredientsTVC];

    [masterVC setViewControllers:@[navigationControllerIngredients]];

    [self.window setRootViewController:masterVC];

    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    return YES;
}
//to save space i didn't copy the autogenerated methods

MasterViewController.h

#import <UIKit/UIKit.h>

@class IngredientsTableViewController;

@interface MasterViewController : UITabBarController {


}

@end

MasterViewController.m

#import "MasterViewController.h"
#import "IngredientsTableViewController.h"

@interface MasterViewController ()

@end

@implementation MasterViewController

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

@end

IngredientsTableViewController.h

import <UIKit/UIKit.h>
#import "DetailIngredientViewController.h"
#import "Ingredient.h"

@interface IngredientsTableViewController : UITableViewController <NSFetchedResultsControllerDelegate, DetailIngredientViewControllerDelegate> {
    Ingredient *ingredient;
}

@property (nonatomic)NSManagedObjectContext *managedObjectContext;
@property (nonatomic)NSFetchedResultsController *fetchedResultsController;
@property (nonatomic)Ingredient *ingredient;
@end

IngredientsTableViewController.m

#import "IngredientsTableViewController.h"


@interface IngredientsTableViewController ()

@end

@implementation IngredientsTableViewController

@synthesize managedObjectContext = _managedObjectContext;
@synthesize fetchedResultsController = _fetchedResultsController;
@synthesize ingredient = _ingredient;



- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.title = @"Ingredients";

    UIBarButtonItem *addButton = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(addIngredient)];
    self.navigationItem.rightBarButtonItem = addButton;
    self.navigationItem.leftBarButtonItem = self.editButtonItem;
}

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

#pragma mark - Table view data source

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

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    id <NSFetchedResultsSectionInfo> sectionInfo = [self.fetchedResultsController sections][section];
    return [sectionInfo numberOfObjects];
} 


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

    // Configure the cell...
    [self configureCell:cell atIndexPath:indexPath];
    return cell;
}

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
        [context deleteObject:[self.fetchedResultsController objectAtIndexPath:indexPath]];
        NSError *error = nil;
        if (![context save:&error]) {
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        }
    }
}

#pragma mark - Action

-

    (void)addIngredient{

        DetailIngredientViewController *detailIngredientVC =[[DetailIngredientViewController alloc]initWithNibName:@"DetailIngredientViewController" bundle:nil];
        detailIngredientVC.delegate = self;

        self.ingredient = [NSEntityDescription insertNewObjectForEntityForName:@"Ingredient" inManagedObjectContext:self.managedObjectContext];
        detailIngredientVC.detailIngredient = self.ingredient;
        [self.navigationController pushViewController:detailIngredientVC animated:YES];


    }

#pragma mark - Fetched Result
- (NSFetchedResultsController *)fetchedResultsController
{
    if (_fetchedResultsController != nil) {
        return _fetchedResultsController;
    }

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Ingredient" inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];

    // Set the batch size to a suitable number.
    [fetchRequest setFetchBatchSize:20];

    // Edit the sort key as appropriate.
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:NO];
    NSArray *sortDescriptors = @[sortDescriptor];

    [fetchRequest setSortDescriptors:sortDescriptors];

    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@"Master"];
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;

    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&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();
    }

    return _fetchedResultsController;
}

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller
{
    [self.tableView beginUpdates];
}

- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
           atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type
{
    switch(type) {
        case NSFetchedResultsChangeInsert:
            [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
       atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
      newIndexPath:(NSIndexPath *)newIndexPath
{
    UITableView *tableView = self.tableView;

    switch(type) {
        case NSFetchedResultsChangeInsert:
            [tableView insertRowsAtIndexPaths:@[newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeUpdate:
            [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
            break;

        case NSFetchedResultsChangeMove:
            [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
            [tableView insertRowsAtIndexPaths:@[newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
    [self.tableView endUpdates];
}


#pragma mark - configureCell:
- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath
{
    NSManagedObject *object = [self.fetchedResultsController objectAtIndexPath:indexPath];
    cell.textLabel.text = [[object valueForKey:@"name"] description];
}

-(void)controller:(UIViewController *)controller didSaveIngredient:(Ingredient *)DetailIngredient{
    NSError *error = nil;
    if (![self.managedObjectContext save:&error]){
        NSLog(@"Error %@ %@", error, [error userInfo]);
    }
}

@end

DetailIngredientViewController.h

#import <UIKit/UIKit.h>
#import "Ingredient.h"

@protocol DetailIngredientViewControllerDelegate;

@interface DetailIngredientViewController : UIViewController {

    IBOutlet UITextField *tfNameIngredient;
    id <DetailIngredientViewControllerDelegate>delegate;
    Ingredient *detailIngredient;
}

@property (nonatomic, retain) IBOutlet UITextField *tfNameIngredient;
@property (nonatomic, retain) id <DetailIngredientViewControllerDelegate>delegate;
@property (nonatomic, retain) Ingredient *detailIngredient;

@end

@protocol DetailIngredientViewControllerDelegate <NSObject>
-(void)controller:(UIViewController *)controller didSaveIngredient:(Ingredient *)DetailIngredient;
@end

DetailIngredientViewController.m

#import "DetailIngredientViewController.h"

@interface DetailIngredientViewController ()

@end

@implementation DetailIngredientViewController

@synthesize tfNameIngredient, detailIngredient;

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

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

-(void)saveIngredient{

    detailIngredient.name = tfNameIngredient.text;
    NSLog(@"1- %@", detailIngredient.name);
    [self.delegate controller:self didSaveIngredient:detailIngredient];
    [self.navigationController popToRootViewControllerAnimated:YES];
}

@end

Answer 1

将以下代码插入您更改数据的TableViewController将解决您的问题：

[self reloadData];

核心数据 - 重新加载TableVIew

1 个答案: