先推薦一個寫得不錯的關於Core Data的文章:http://blog.csdn.net/q199109106q/article/details/8563438
還有:http://my.oschina.net/pljhonglu/blog/199668#OSC_h3_4
還有:http://my.oschina.net/jackyyang/blog/66641
先提出兩個問題吧;
1.什麼是Core Data?
2.Core Data的原理和整個處理過程是什麼?
1.什麼是Core Data?
2.Core Data的原理和整個處理過程是什麼?
- (id)init
{
if (defaultStore) {
return defaultStore;
}
self = [super init];
// if (self) {
// allPossessions = [[NSMutableArray alloc] init];
// }
//讀入Homepwner.xcdatamodeld這是通過模型文件建立的
model = [[NSManagedObjectModel mergedModelFromBundles:nil] retain];
NSLog(@"model= %@",model);
NSPersistentStoreCoordinator *persisStoreCordor = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
//設置SQLite文件路徑
NSString *path = pathInDocumentDirectory(@"store.data");
NSURL *storeURL = [NSURL fileURLWithPath:path];
NSError *error = nil;
if (![persisStoreCordor addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
[NSException raise:@"Open failed" format:@"Reason: %@",[error localizedDescription]];
}
//創建NSManagedObjectContext對象
context = [[NSManagedObjectContext alloc] init];
[context setPersistentStoreCoordinator:persisStoreCordor];
[persisStoreCordor release];
//NSManagedObjectContext對象可以管理撤銷(undo)操作,Homepwner不需要該功能
[context setUndoManager:nil];
return self;
}
- (BOOL)saveChanges {
//return [NSKeyedArchiver archiveRootObject:allPossessions toFile:[self possessionArchivePath]];
NSError *err = nil;
BOOL successful = [context save:&err];//保存數據
if (!successful) {
NSLog(@"Error saving: %@",[err localizedDescription]);
}
return successful;
}
- (void)fetchPossessionIfNecessary {
if (!allPossessions) {
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
NSEntityDescription *entity = [[model entitiesByName] objectForKey:@"Possession"];
[request setEntity:entity];
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"orderingValue" ascending:YES];
[request setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];
NSError *error;
NSArray *result = [context executeFetchRequest:request error:&error];
if (!result) {
[NSException raise:@"Fetch failed" format:@"Reason: %@",[error localizedDescription]];
}
allPossessions = [[NSMutableArray alloc] initWithArray:result];
}
}