[英]Why won't my model save to Core Data?
我對Objective-C很陌生,我正試圖搞亂Core Data。 我有以下App Delegate接口和實現:
#import <UIKit/UIKit.h>
@interface SDTAppDelegate : UIResponder <UIApplicationDelegate>
@property (strong, nonatomic) UIWindow *window;
@property (nonatomic, strong) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, strong) NSManagedObjectModel *managedObjectModel;
@property (nonatomic, strong) NSPersistentStoreCoordinator *persistentStoreCoordinator;
- (void)saveManagedObjectContext;
- (NSManagedObjectContext *)setupManagedObjectContext;
- (NSManagedObjectModel *)setupManagedObjectModel;
- (NSPersistentStoreCoordinator *)setupPersistentStoreCoordinator;
- (NSURL *)applicationDocumentsDirectory;
@end
履行
#import "SDTAppDelegate.h"
#import "ToDoItem.h"
@implementation SDTAppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Get the managed object context and associate it to the app delegate
self.managedObjectContext = [self setupManagedObjectContext];
return YES;
}
- (void)applicationWillTerminate:(UIApplication *)application
{
[self saveManagedObjectContext];
}
/**
* Save the MOC!
*/
- (void)saveManagedObjectContext
{
NSError *error = nil;
if (self.managedObjectContext != nil)
{
if ([self.managedObjectContext hasChanges] && ![self.managedObjectContext save:&error])
{
/*
THIS NEEDS TO BE REPLACED
*/
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
}
}
#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 *)setupManagedObjectContext
{
if (self.managedObjectContext != nil)
{
return self.managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self setupPersistentStoreCoordinator];
if (coordinator != nil)
{
self.managedObjectContext = [[NSManagedObjectContext alloc] init];
[self.managedObjectContext setPersistentStoreCoordinator:coordinator];
}
return self.managedObjectContext;
}
/**
* Return the managed object model. If it doesn't exist, create it.
*/
- (NSManagedObjectModel *)setupManagedObjectModel
{
if (self.managedObjectModel != nil)
{
return self.managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Model" withExtension:@"momd"];
self.managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return self.managedObjectModel;
}
/**
* Return the persistent store coordinator. If it doesn't exist, create it.
*/
- (NSPersistentStoreCoordinator *)setupPersistentStoreCoordinator
{
if (self.persistentStoreCoordinator != nil)
{
return self.persistentStoreCoordinator;
}
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Model.sqlite"];
NSError *error = nil;
self.persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self setupManagedObjectModel]];
if (![self.persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
configuration:nil
URL:storeURL
options:nil
error:&error])
{
/*
THIS NEEDS TO BE REPLACED
*/
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return self.persistentStoreCoordinator;
}
#pragma mark - Application's Documents directory
/**
* Return the URL to the application's Documents directory.
*/
- (NSURL *)applicationDocumentsDirectory
{
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
@end
然后在我的控制器中我有以下保存新模型:
// Take the managed object context from the app delegate
SDTAppDelegate *appDelegate = (SDTAppDelegate *)[UIApplication sharedApplication].delegate;
NSManagedObjectContext *context = appDelegate.managedObjectContext;
// Add the new item
ToDoItem *newItem = [NSEntityDescription insertNewObjectForEntityForName:@"ToDoItem" inManagedObjectContext:context];
newItem.item = self.textField.text;
newItem.completed = 0;
無論發生什么,我都無法保存應用程序。 它在界面中顯示正常,但是當我退出並重新啟動時,數據不再存在。 我猜這是我的持久存儲有問題嗎?
您應該保存上下文以便保存在持久性存儲中。
NSError *error;
[context save:&error];
希望能幫助到你。 干杯
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