도움 받은 곳 : http://natashatherobot.com/ios-core-data-singleton-example/
db가 필요한 예제 만들다가 sqlite 클래스 만들기 귀찮아서 이 참에 core data를 써봐야겠다 싶어서 이 예제를 만들었다.
#import <Foundation/Foundation.h>
@interface DBManager : NSObject
+ (DBManager*) sharedInstance;
- (NSFetchedResultsController*) fetchAllWithClassName:(NSString*)className
cacheName:(NSString*)cacheName;
- (NSFetchedResultsController *)fetchEntitiesWithClassName:(NSString *)className
sortDescriptors:(NSArray *)sortDescriptors
sectionNameKeyPath:(NSString *)sectionNameKeypath
predicate:(NSPredicate *)predicate;
- (void)saveWithBlock:(void (^)(BOOL saved, NSError *error))savedBlock;
- (void)deleteEntity:(NSManagedObject *)entity;
- (id)createEntityWithClassName:(NSString *)className
attributesDictionary:(NSDictionary *)attributesDictionary;
@end
#import "DBManager.h"
@interface DBManager()
@property (strong, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (strong, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
@property (strong, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;
@end
@implementation DBManager
static DBManager *_instance;
+(DBManager*) sharedInstance
{
if (!_instance)
{
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
_instance = [DBManager new];
});
}
return _instance;
}
-(id) init
{
self = [super init];
if (self)
{
[self connect];
}
return self;
}
-(void)connect
{
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"TestCoreData" withExtension:@"momd"];
self.managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
self.persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:self.managedObjectModel];
NSURL *documentsDirectory =[[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
NSURL *storeURL = [documentsDirectory URLByAppendingPathComponent:@"TestCoreData3.sqlite"];
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES],NSMigratePersistentStoresAutomaticallyOption,
[NSNumber numberWithBool:YES],NSInferMappingModelAutomaticallyOption,
nil];
NSError *error = nil;
if (![self.persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
configuration:nil URL:storeURL
options:options error:&error]) {
NSLog(@"===============\nUnresolved error %@, %@", error, [error userInfo]);
abort();
}
else
{
self.managedObjectContext = [NSManagedObjectContext new];
[self.managedObjectContext setPersistentStoreCoordinator:self.persistentStoreCoordinator];
}
}
- (NSFetchedResultsController*) fetchAllWithClassName:(NSString*)className
cacheName:(NSString*)cacheName
{
NSFetchRequest *fetchRequest = [NSFetchRequest new];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:className inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
[fetchRequest setFetchBatchSize:20];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"createdAt" ascending:NO];
NSArray *sortDescriptors = @[sortDescriptor];
[fetchRequest setSortDescriptors:sortDescriptors];
NSFetchedResultsController *fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
managedObjectContext:self.managedObjectContext
sectionNameKeyPath:nil
cacheName:cacheName];
NSError *error = nil;
if (![fetchedResultsController performFetch:&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.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return fetchedResultsController;
}
- (NSFetchedResultsController *)fetchEntitiesWithClassName:(NSString *)className
sortDescriptors:(NSArray *)sortDescriptors
sectionNameKeyPath:(NSString *)sectionNameKeypath
predicate:(NSPredicate *)predicate
{
NSFetchedResultsController *fetchedResultsController;
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:className
inManagedObjectContext:self.managedObjectContext];
fetchRequest.entity = entity;
fetchRequest.sortDescriptors = sortDescriptors;
fetchRequest.predicate = predicate;
fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
managedObjectContext:self.managedObjectContext
sectionNameKeyPath:sectionNameKeypath
cacheName:nil];
NSError *error = nil;
BOOL success = [fetchedResultsController performFetch:&error];
if (!success) {
NSLog(@"fetchManagedObjectsWithClassName ERROR: %@", error.description);
}
return fetchedResultsController;
}
- (id)createEntityWithClassName:(NSString *)className
attributesDictionary:(NSDictionary *)attributesDictionary
{
NSManagedObject *entity = [NSEntityDescription insertNewObjectForEntityForName:className
inManagedObjectContext:self.managedObjectContext];
NSMutableDictionary* dictionary = [NSMutableDictionary dictionaryWithDictionary:attributesDictionary];
[dictionary setValue:[NSDate date] forKey:@"createdAt"];
[dictionary setValue:[NSDate date] forKey:@"updatedAt"];
[dictionary enumerateKeysAndObjectsUsingBlock:^(NSString *key, id obj, BOOL *stop) {
[entity setValue:obj forKey:key];
}];
return entity;
}
- (void)saveWithBlock:(void (^)(BOOL saved, NSError *error))savedBlock
{
NSError *saveError = nil;
savedBlock([self.managedObjectContext save:&saveError], saveError);
}
- (void)deleteEntity:(NSManagedObject *)entity
{
[self.managedObjectContext deleteObject:entity];
}
@end
일단 이렇게 하면 어느 정도 필요한 건 다 된 것 같다.
그냥 sqlite 랑 비슷하다고만 생각했는데, 개념이 많이 달라서 고생 좀 했다 ㅠㅠ
보통의 db는 select하고, insert하는 걸 바로바로 해줘야하는데, 얘는 그런거 없이 배열 정보로 갖고 있다가 한방에 저장시켜 버린다.
그래서 core data 예제를 만들면 앱이 꺼질 때 딱 한 번 save를 한다….
이거 때문에 아주 많이 헤맸다.
근데 이거 테이블 많아지면서, 관계설정 들어가기 시작하면 감당 안되지 싶은데 ;;;;;
// fetch all //self.fetchedResultsController = [self.dbManager fetchAllWithClassName:@"Event" cacheName:@"Master"]; // fetch with sort NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES]; NSArray *sortDescriptors = @[sortDescriptor]; self.fetchedResultsController = [[DBManager sharedInstance] fetchEntitiesWithClassName:@"Event" sortDescriptors:sortDescriptors sectionNameKeyPath:nil predicate:nil]; self.fetchedResultsController.delegate = self; // count NSLog(@"count : %d", self.fetchedResultsController.fetchedObjects.count); // get one NSManagedObject *object = [self.fetchedResultsController.fetchedObjects objectAtIndex:0]; NSLog(@"info : %@", [object valueForKey:@"name"]);
select 는 이렇게 하면 된다.
where 절에 해당하는 predicate는 NSPredicate 로 검색하는게 나을 것 같다.
보통의 where와는 많이 달라서 테스트를 해보는게 좋을 듯…..
NSManagedObject *object = [self.fetchedResultsController.fetchedObjects objectAtIndex:0]; [object setValue:self.nameField.text forKey:@"name"];
fetchedResultsController에서 NSManagerObject를 가져오고, 그거의 특정 key에 해당하는 value를 바꿔주면 된다.
NSDictionary와 사용법은 같다고 생각하면 이해하기 편하다.
NSMutableDictionary *dictionary = [NSMutableDictionary new]; [dictionary setValue:self.nameField.text forKey:@"name"]; [[DBManager sharedInstance] createEntityWithClassName:@"Event" attributesDictionary:dictionary];
Event 모델의 name에 값을 넣어서 배열에 저장하는 부분이다.
보통의 db였다면 이 부분에서 insert 쿼리가 실행됐을 테지만, core data는 그런거 없다.
[[DBManager sharedInstance] saveWithBlock:^(BOOL saved, NSError *error) {
if (!saved)
NSLog(@"error : %@", error);
else
[self.navigationController popViewControllerAnimated:YES];
}];
실제로는 이런 식으로 save를 날려줘야 저장된다.
이러면 fetchedResults 에 변경된 놈, 추가된 놈, 수정된 놈들의 쿼리가 날아간다.
특히 이 부분 때문에 이해하기 정말 힘들었다.
전체 소스는 https://github.com/susemi99/TestCoreData 에 올려뒀다.