我将以下代码用于核心数据单例。下面是我的代码。(基于 NachoMan 的博客。但是代码来自他的要点。
// DataManager.h
#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>
extern NSString * const DataManagerDidSaveNotification;
extern NSString * const DataManagerDidSaveFailedNotification;
@interface DataManager : NSObject {
}
@property (nonatomic, readonly, retain) NSManagedObjectModel *objectModel;
@property (nonatomic, readonly, retain) NSManagedObjectContext *mainObjectContext;
@property (nonatomic, readonly, retain) NSPersistentStoreCoordinator *persistentStoreCoordinator;
@property (nonatomic, readonly, retain) NSManagedObjectContext *managedObjectContext;
+ (DataManager*)sharedInstance;
- (BOOL)save;
- (BOOL)clearEntity:(NSString *)entityDescription;
- (NSManagedObjectContext*)managedObjectContext;
@end
// DataManager.m
#import "DataManager.h"
NSString * const DataManagerDidSaveNotification = @"DataManagerDidSaveNotification";
NSString * const DataManagerDidSaveFailedNotification = @"DataManagerDidSaveFailedNotification";
@interface DataManager ()
- (NSString*)sharedDocumentsPath;
@end
@implementation DataManager
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;
@synthesize mainObjectContext = _mainObjectContext;
@synthesize objectModel = _objectModel;
@synthesize managedObjectContext = _managedObjectContext;
NSString * const kDataManagerBundleName = nil;//@"AP";
NSString * const kDataManagerModelName = @"APData";
NSString * const kDataManagerSQLiteName = @"APData.sqlite";
+ (DataManager*)sharedInstance {
static dispatch_once_t pred;
static DataManager *sharedInstance = nil;
dispatch_once(&pred, ^{ sharedInstance = [[self alloc] init]; });
return sharedInstance;
}
- (void)dealloc {
[self save];
}
- (NSManagedObjectModel*)objectModel {
if (_objectModel)
return _objectModel;
NSBundle *bundle = [NSBundle mainBundle];
if (kDataManagerBundleName) {
NSString *bundlePath = [[NSBundle mainBundle] pathForResource:kDataManagerBundleName ofType:@"bundle"];
bundle = [NSBundle bundleWithPath:bundlePath];
}
NSString *modelPath = [bundle pathForResource:kDataManagerModelName ofType:@"momd"];
NSLog(@"Path: %@",modelPath);
_objectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:[NSURL fileURLWithPath:modelPath]];
return _objectModel;
}
- (NSPersistentStoreCoordinator*)persistentStoreCoordinator {
if (_persistentStoreCoordinator) {
NSLog(@"PersistentStore Exists %@",_persistentStoreCoordinator);
return _persistentStoreCoordinator;
}
NSLog(@"Persistent Stored DOESN'T EXIST");
// Get the paths to the SQLite file
NSString *storePath = [[self sharedDocumentsPath] stringByAppendingPathComponent:kDataManagerSQLiteName];
NSURL *storeURL = [NSURL fileURLWithPath:storePath];
// Define the Core Data version migration options
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
[NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption,
nil];
// Attempt to load the persistent store
NSError *error = nil;
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:self.objectModel];
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
configuration:nil
URL:storeURL
options:options
error:&error]) {
NSLog(@"Fatal error while creating persistent store: %@", error);
abort();
}
NSLog(@"store: %@",_persistentStoreCoordinator);
return _persistentStoreCoordinator;
}
- (NSManagedObjectContext*)mainObjectContext {
if (_mainObjectContext)
return _mainObjectContext;
// Create the main context only on the main thread
if (![NSThread isMainThread]) {
[self performSelectorOnMainThread:@selector(mainObjectContext)
withObject:nil
waitUntilDone:YES];
return _mainObjectContext;
}
_mainObjectContext = [[NSManagedObjectContext alloc] init];
[_mainObjectContext setPersistentStoreCoordinator:self.persistentStoreCoordinator];
return _mainObjectContext;
}
- (BOOL)save {
if (![self.mainObjectContext hasChanges])
return YES;
NSError *error = nil;
if (![self.mainObjectContext save:&error]) {
NSLog(@"Error while saving: %@\n%@", [error localizedDescription], [error userInfo]);
[[NSNotificationCenter defaultCenter] postNotificationName:DataManagerDidSaveFailedNotification
object:error];
return NO;
}
[[NSNotificationCenter defaultCenter] postNotificationName:DataManagerDidSaveNotification object:nil];
return YES;
}
- (BOOL)clearEntity:(NSString *)entityDescription
{
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:entityDescription inManagedObjectContext:_managedObjectContext];
[fetchRequest setEntity:entity];
NSError *error;
NSArray *items = [_managedObjectContext executeFetchRequest:fetchRequest error:&error];
for (NSManagedObject *managedObject in items) {
[_managedObjectContext deleteObject:managedObject];
NSLog(@"%@ object deleted",entityDescription);
}
if (![_managedObjectContext save:&error]) {
NSLog(@"Error deleting %@ - error:%@",entityDescription,error);
return NO;
}
return YES;
}
- (NSString*)sharedDocumentsPath {
static NSString *SharedDocumentsPath = nil;
if (SharedDocumentsPath)
return SharedDocumentsPath;
// Compose a path to the <Library>/Database directory
NSString *libraryPath = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) objectAtIndex:0];
SharedDocumentsPath = [libraryPath stringByAppendingPathComponent:@"Database"];
// Ensure the database directory exists
NSFileManager *manager = [NSFileManager defaultManager];
BOOL isDirectory;
if (![manager fileExistsAtPath:SharedDocumentsPath isDirectory:&isDirectory] || !isDirectory) {
NSError *error = nil;
NSDictionary *attr = [NSDictionary dictionaryWithObject:NSFileProtectionComplete
forKey:NSFileProtectionKey];
[manager createDirectoryAtPath:SharedDocumentsPath
withIntermediateDirectories:YES
attributes:attr
error:&error];
if (error)
NSLog(@"Error creating directory path: %@", [error localizedDescription]);
}
return SharedDocumentsPath;
}
- (NSManagedObjectContext*)managedObjectContext {
if (_managedObjectContext) {
return _managedObjectContext;
}
_managedObjectContext = [[NSManagedObjectContext alloc] init];
NSUndoManager *undoManager = [[NSUndoManager alloc] init];
[_managedObjectContext setUndoManager:undoManager];
[_managedObjectContext setPersistentStoreCoordinator:self.persistentStoreCoordinator];
[_mainObjectContext setRetainsRegisteredObjects:YES];
return _managedObjectContext;
}
@end
但是,managedObjectContext
如果我添加
NSUndoManager *undoManager = [[NSUndoManager alloc] init];
[_managedObjectContext setUndoManager:undoManager];
它会崩溃。
Crittercism日志显示
SIGBUS
主要 (main.m:16)
0 CoreData 0x0033d940 -[NSManagedObject(_NSInternalMethods) _newSnapshotForUndo__] + 352
1 CoreData 0x00318fb1 -[NSManagedObjectContext(_NSInternalChangeProcessing) _registerUndoForOperation:withObjects:withExtraArguments:] + 193
2 CoreData 0x0031922f -[NSManagedObjectContext(_NSInternalChangeProcessing) _registerUndoForInsertedObjects:] + 63
3 CoreData 0x003148f8 -[NSManagedObjectContext(_NSInternalChangeProcessing) _processRecentChanges:] + 1384
4 CoreData 0x00314389 -[NSManagedObjectContext processPendingChanges] + 41
5 CoreData 0x002e8bd8 _performRunLoopAction + 216
6 CoreFoundation 0x0177d99e __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 30
7 CoreFoundation 0x01714640 __CFRunLoopDoObservers + 384
8 CoreFoundation 0x016e04c6 __CFRunLoopRun + 1174
9 CoreFoundation 0x016dfd84 CFRunLoopRunSpecific + 212
10 CoreFoundation 0x016dfc9b CFRunLoopRunInMode + 123
11 GraphicsServices 0x023617d8 GSEventRunModal + 190
12 GraphicsServices 0x0236188a GSEventRun + 103
13 UIKit 0x007e2626 UIApplicationMain + 1163
14 My-App 0x284d main (main.m:16)
15 My-App 0x27b5 start + 53
当很多SO帖子说要使用它时,为什么这两条线会崩溃?如果我把这两条线去掉,它就不会崩溃,我只是无法使用撤消管理器。