我已经使用核心数据构建了我的应用程序，但是我在如何计算保存和加载方面遇到了麻烦。
我有一个UIDatePicker。 我有一个UITextView。
我想保存用户在UITextView中输入的内容。 然后，如果用户选择他们最初保存它的相同日期，我想将该文本加载回UITextView。
喜欢日历。
希望你能，我能解决它。
编辑：
这是我的目标，当然不起作用。希望你能进一步提升。 http://b.imagehost.org/view/0307/Screen_shot_2010-11-09_at_19_43_57
编辑2： 好的，这是我的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（无论如何，无论如何，围绕此的所有代码都可以忽略，因为它无关紧要，与UIDatePicker（datePicker）或UITextView（notesView）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];
}
答案 0 :(得分：2)
当您添加或编辑任何对象时，应将该对象保存在MOC（ManagedObjectContect）中。
以下是修改后的代码：
-(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]);
}
}
答案 1 :(得分：2)
好吧，首先，尝试了解核心数据的工作原理。我觉得你很接近，但编程就是要真正知道发生了什么，而不是'有点'知道发生了什么。 Getting started with Core Data"指南非常有启发性。
现在关于你的代码（我不知道你是精确的数据模型和周围的代码，所以我在这里猜测）。我假设你有一个名为'datePicker'的成员，它指的是你正在使用的日期选择器。
好吧，让我看看我是否可以快速修复代码中的一些内容，但要小心一点。我没有阅读你的源代码的每一行，我还没有尝试编译它，所以可能仍然会有错误。最后，您仍然可以彻底了解代码。
- (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];
}
答案 2 :(得分：0)
如果你的数据库中有一个文本输入实体，只需给它一个类型为date的属性，然后选择“indexed”。
然后我会像这样开始一个NSFetchRequest：
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时。数组将为空或保存文本条目。 虽然也许你应该先阅读"Developing with Core Data"。