objective-c - 核心数据需要帮助

Question

如何在核心数据中添加 NSDictionary 任何文档或示例代码都会有所帮助。提前致谢。

Answer 1

在新项目窗口中，选择任何模板选项。在窗口的选项部分中，确保选中使用核心数据进行存储旁边的复选框，单击选择

在里面AppDelegate.h

@class coreDataViewController;

@interface coreDataAppDelegate : NSObject <UIApplicationDelegate> {

NSManagedObjectModel *managedObjectModel;
NSManagedObjectContext *managedObjectContext;
NSPersistentStoreCoordinator *persistentStoreCoordinator;

coreDataViewController *viewController;

UIWindow *window;
 }

@property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel;
@property (nonatomic, retain, readonly) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, retain, readonly) NSPersistentStoreCoordinator    *persistentStoreCoordinator;
@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet coreDataViewController *viewController;
- (NSString *)applicationDocumentsDirectory;
@end

在您的视图控制器：

// 保存数据

- (void) saveData
{
    coreDataAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
    NSManagedObjectContext *context = [appDelegate managedObjectContext];
    NSManagedObject *newContact;
    newContact = [NSEntityDescription insertNewObjectForEntityForName:@"Contacts" inManagedObjectContext:context];
    [newContact setValue:@"anyData" forKey:@"anyKeyInDataBase"];
    [newContact setValue:@"anyData" forKey:@"anyKeyInDataBase"];
    [newContact setValue:@"anyData" forKey:@"anyKeyInDataBase"];
    NSError *error;
    [context save:&error];
 }

// 检索数据

 - (void) findContact
 {
    coreDataAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];

    NSManagedObjectContext *context = [appDelegate managedObjectContext];

    NSEntityDescription *entityDesc = [NSEntityDescription entityForName:@"Contacts" inManagedObjectContext:context];

    NSFetchRequest *request = [[NSFetchRequest alloc] init];

    [request setEntity:entityDesc];

    NSPredicate *pred = [NSPredicate predicateWithFormat:@"(yourPrimaryKey = %@)", @"theKeyYouSearchFor"];

    [request setPredicate:pred];

    NSManagedObject *matches = nil;
    NSError *error;

    NSArray *objects = [context executeFetchRequest:request error:&error];

    if ([objects count] == 0) {
             NSLog( @"No matches");
    } else {
            matches = [objects objectAtIndex:0];
             NSLog( @"%@",[matches valueForKey:@"anyKey"]);
             NSLog( @"%@",[matches valueForKey:@"anyKey"]);
             NSLog( @"%@",[matches valueForKey:@"anyKey"]);

    }
    [request release];
}

它可以正常工作