核心数据iPhone - 保存/加载取决于日期

Question

我已经使用核心数据构建了我的应用程序，但我遇到了如何解决保存和加载问题。

我有一个UIDatePicker。 我有一个UITextView。

我想保存用户在UITextView中键入的内容。 然后，如果用户选择它们最初保存的相同日期，我想将该文本加载回UITextView。

就像日历一样。

希望你能，我可以解决它。编辑：

这是我去，当然不工作。希望你能进一步帮助。 http://b.imagehost.org/view/0307/Screen_shot_2010-11-09_at_19_43_57

编辑2： 好吧，这里是我的appDelegate.h

#import <UIKit/UIKit.h> 
#import <CoreData/CoreData.h> 

@class coreDataViewController; 

@interface OrganizerAppDelegate : 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 

appDelegate.m

#import "OrganizerAppDelegate.h" 
#import "coreDataViewController.h" 

@implementation OrganizerAppDelegate 

@synthesize window; 
@synthesize viewController; 

@synthesize managedObjectModel; 
@synthesize managedObjectContext; 
@synthesize persistentStoreCoordinator; 

#pragma mark - 
#pragma mark Application lifecycle 

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

    // Override point for customization after app launch 
    [window addSubview:viewController.view]; 
    [window makeKeyAndVisible]; 

    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)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. 
    */ 
} 


/** 
applicationWillTerminate: saves changes in the application's managed object context before the application terminates. 
*/ 
- (void)applicationWillTerminate:(UIApplication *)application { 

    NSError *error = nil; 
    if (managedObjectContext != 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. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button. 
      */ 
      NSLog(@"Unresolved error %@, %@", error, [error userInfo]); 
      abort(); 
     } 
    } 
} 


#pragma mark - 
#pragma mark Core Data stack 

/** 
Returns the managed object context for the application. 
If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application. 
*/ 
- (NSManagedObjectContext *)managedObjectContext { 

    if (managedObjectContext != nil) { 
     return managedObjectContext; 
    } 

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


/** 
Returns the managed object model for the application. 
If the model doesn't already exist, it is created from the application's model. 
*/ 
- (NSManagedObjectModel *)managedObjectModel { 

    if (managedObjectModel != nil) { 
     return managedObjectModel; 
    } 
    NSString *modelPath = [[NSBundle mainBundle] pathForResource:@"Organizer" ofType:@"momd"]; 
    NSURL *modelURL = [NSURL fileURLWithPath:modelPath]; 
    managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];  
    return managedObjectModel; 
} 


/** 
Returns the persistent store coordinator for the application. 
If the coordinator doesn't already exist, it is created and the application's store added to it. 
*/ 
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator { 

    if (persistentStoreCoordinator != nil) { 
     return persistentStoreCoordinator; 
    } 

    NSURL *storeURL = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"Organizer.sqlite"]]; 

    NSError *error = nil; 
    persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; 
    if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&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. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button. 

     Typical reasons for an error here include: 
     * The persistent store is not accessible; 
     * The schema for the persistent store is incompatible with current managed object model. 
     Check the error message to determine what the actual problem was. 


     If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory. 

     If you encounter schema incompatibility errors during development, you can reduce their frequency by: 
     * Simply deleting the existing store: 
     [[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil] 

     * Performing automatic lightweight migration by passing the following dictionary as the options parameter: 
     [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES],NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil]; 

     Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details. 

     */ 
     NSLog(@"Unresolved error %@, %@", error, [error userInfo]); 
     abort(); 
    }  

    return persistentStoreCoordinator; 
} 


#pragma mark - 
#pragma mark Application's Documents directory 

/** 
Returns the path to the application's Documents directory. 
*/ 
- (NSString *)applicationDocumentsDirectory { 
    return [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject]; 
} 


#pragma mark - 
#pragma mark Memory management 

- (void)dealloc { 

    [managedObjectContext release]; 
    [managedObjectModel release]; 
    [persistentStoreCoordinator release]; 

    [window release]; 
    [super dealloc]; 
} 


@end 

viewController.m（位认为反正事情，这周围的所有代码可以忽略，因为它与UIDatePicker（datePicker）或UITextView（notesView）无关，与它无关。

-(void)textViewDidEndEditing:(UITextView *)textView { 
    NSManagedObjectContext *context = [OrganizerAppDelegate managedObjectContext]; 
    NSManagedObject *note = [NSEntityDescription insertNewObjectForEntityForName:@"Notes" inManagedObjectContext:context]; 
    [note setValue:notesView.text forKey:@"text"]; 
    [note valueForKey:@"text"]; 

    NSError *err=nil; if (![context save:&err]) { NSLog(@"Whoops, couldn't save: %@", [err localizedDescription]); } } 

    NSDate *dtTemp = [pkrDate.date retain]; 
    NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease]; 
    [dateFormatter setDateFormat:@"HH"]; 
    hour = [[dateFormatter stringFromDate:dtTemp]intValue]; 
    [dateFormatter setDateFormat:@"mm"]; 
    mins = [[dateFormatter stringFromDate:dtTemp]intValue]; 
    [dateFormatter setDateFormat:@"ss"]; 
    sec = [[dateFormatter stringFromDate:dtTemp]intValue]; 
    NSTimeInterval *timeInterval = [dtTemp timeIntervalSince1970]; 
    timeInterval = timeInterval - (hour*3600+mins*60+sec); 
    timeStamp = [[NSDate dateWithTimeIntervalSince1970:timeInterval]retain]; 

- (void) dateChanged:(id)sender{ 

    //Load... 
    NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Text" inManagedObjectContext:self.managedObjectContext]; 
    NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease]; 
    [request setEntity:entityDescription]; 

    NSPredicate *predicate = [NSPredicate predicateWithFormat: 
           @"(timeStamp = %@)",datePicker.date]; 
    [request setPredicate:predicate]; //added this line later 
    NSArray *array = [self.managedObjectContext executeFetchRequest:request error:&error]; 
    //check whether the array has entrys and do something with those objects here 

    [monTable reloadData]; 
    [tueTable reloadData]; 
    [wedTable reloadData]; 
    [thuTable reloadData]; 
    [friTable reloadData]; 
} 

Answer 1

还好吧，首先，试着去理解数据的方式的核心工作。我认为你非常接近，但编程是关于真正了解正在发生的事情，而不是'知道'发生了什么。 Getting started with Core Data"指南非常具有启发性。现在你的代码（我不知道你是确切的数据模型和周围的代码，所以我有点猜测在这里）。我假设你有一个名为'datePicker'的成员，它引用了你正在使用的datepicker。

好吧，让我看看我能否快速修复代码中的某些内容，但要小心一点。我没有阅读你的源代码的每一行，我还没有试过编译它，所以可能仍然会有错误。最后，您仍然会彻底了解代码。

- (void)textViewDidEndEditing:(UITextView *)textView { 
    NSManagedObjectContext *context = [OrganizerAppDelegate managedObjectContext]; 
    NSManagedObject *note = [NSEntityDescription insertNewObjectForEntityForName:@"Notes" inManagedObjectContext:context]; 
    [note setValue:notesView.text forKey:@"text"]; 

    // Set the timestamp as well. 
    [note setValue:datePicker.date forKey:@"timeStamp"]; 

    NSError *err=nil; if (![context save:&err]) { NSLog(@"Whoops, couldn't save: %@", [err localizedDescription]); } } 

/* Beware, we're just storing every edit here, without every throwing anything away. We'll try to display just the latest note in the 'dateChanged', but you might want to delete any previous notes first.*/ 

/* I don't think this whole dissecting and generating a date is necessary */ 

- (void) dateChanged:(id)sender{ 

    //Load... 
    NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Text" inManagedObjectContext:self.managedObjectContext]; 
    NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease]; 
    [request setEntity:entityDescription]; 

    NSPredicate *predicate = [NSPredicate predicateWithFormat: 
           @"(timeStamp = %@)",datePicker.date]; 
    [request setPredicate:predicate]; //added this line later 
    NSArray *array = [self.managedObjectContext executeFetchRequest:request error:&error]; 

    // Assuming that the last item in the array is the item that was added last. This might or might not be reasonable. 
    notesView.text = [[array lastObject] text]; 

    [monTable reloadData]; 
    [tueTable reloadData]; 
    [wedTable reloadData]; 
    [thuTable reloadData]; 
    [friTable reloadData]; 
} 

Answer 2

那么，如果你的数据库中有一个文本输入实体，就给它一个date类型的属性并选择“indexed”。

然后我会开始一个NSFetchRequest这样的：

NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Text" 
inManagedObjectContext:self.managedObjectContext]; 
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease]; 
[request setEntity:entityDescription]; 

NSPredicate *predicate = [NSPredicate predicateWithFormat: 
          @"(timeStamp = %@)",datepicker.date]; 
[request setPredicate:predicate]; //added this line later 
NSArray *array = [self.managedObjectContext executeFetchRequest:request error:&error]; 
//check whether the array has entrys and do something with those objects here 

当用户更改日期选择器的日期。数组将为空或保存文本条目。 虽然也许你应该先通读"Developing with Core Data"。

Answer 3

当您添加或编辑任何对象时，应该将该对象保存在MOC（ManagedObjectContect）中。

下面是修改代码：

-(void)textViewDidEndEditing:(UITextView *)textView{ 
NSManagedObjectContext *context=[YourAppDelegate managedObjectContext]; 
NSManagedObject *note=[NSEntityDescription insertNewObjectForEntityForName:@"Notes" inManagedObjectContext:context]; 
[note setValue:notesView.text forKey:@"text"]; 
[note valueForKey:@"text"] ; 

NSError *err=nil; 
if (![context save:&err]) { 
    NSLog(@"Whoops, couldn't save: %@", [err localizedDescription]); 
} 
}