[IPHONE] Using Core Data
CS/iPhone 2012. 1. 12. 23:20- NSManagedObject의 서브클래스에 대해 작성하는 accessor methods의 구현에는 일반적으로 다른 클래스를 작성하는것과는 다르다.
- 만약 custom instance variable을 제공하지 않는다면, primitive accessor method를 사용하여 internal store로 값을 저장하고, internal store로 부터 property value를 가져오게 된다.
- NSManagedObject 는 modeld properties에 대해서 automatic KVO change notification 을 비활성화 하며, primitive accessor methods는 access notification method와 change notification method를 invoke하지 않는다.
- Entity model에서 정의되지 않은 property들의 accessor method에서, automatic change notification을 활성화 하거나 적절한 change notification method를 invoke할 수 있다.
NSManagedObject *newEmployee = [NSEntityDescription insertNewObjectForEntityForName:@"Employee"
inManagedObjectContext:context];
NSManagedObject *newEmployee = [[NSManagedObject alloc] initWithEntity:employeeEntity
insertIntoManagedObjectContext:context];
NSManagedObjectContext *context = <#Get a context#>;
NSManagedObjectModel *managedObjectModel = [[context persistentStoreCoordinator] managedObjectModel];
NSEntityDescription *employeeEntity = [[managedObjectModel entitiesByName] objectForKey:@"Employee"];
NSManagedObjectContext *context = <#Get a context#>;
NSEntityDescription *employeeEntity = [NSEntityDescription entityForName:@"Employee"
inManagedObjectContext:context];
NSManagedObjectContext *context = <#Get a context#>;
[context deleteObject:managedObject];
- managed object context에 deleteObject: 메세지를 보내면, context는 NSManagedObjectContextObjectsDidChangeNotification 통지를 post한다.
- 만약 object가 동일한 transaction에서 create되고 delete 된다면, managed object context의 deletedObject 의 결과 array나 NSManagedObjectContextDidSaveNotification 통지의 deleted object set에 나타나지 않을 것이다.
NSMutableSet *employees = [aDepartment mutableSetValueForKey:@"employees"];
[employees addObject:newEmployee];
[employees removeObject:firedEmployee];
// or
[aDepartment addEmployeesObject:newEmployee];
[aDepartment removeEmployeesObject:firedEmployee];
- mutableSetValueForKey: 에 의해 리턴되는 값과 dot accessor method에 의해 리턴되는 값의 차이를 이해하는 것은 중요하다.
- mutableSetValueForKey:는 mutable proxy object를 리턴한다.
- 만약 그것의 내용을 바꾼다면, relationship에 대한 적절한 KVO change 통지를 emit 할 것이다.
- dot accessor 는 단순히 set을 리턴한다.
- 만약 [aDepartment.employees addObject:newEmployee] 와 같이 한다면, KVO change notification은 emit 되지 않을 것이며, inverse relationship은 적절하게 update되지 않을 것이다.
- dot 은 accessor method를 invoke 하기 떄문에, [[aDepartment employees] addObject:newEmployee]; 도 같은 결과이다.
- Core Data 는 object graph의 consistency를 관리하기 때문에, 관계의 한쪽 끝만을 변경하면 다른 면은 Core Data 가 관리해 준다.
anEmployee.department = newDepartment;
or
[newDepartment addEmployeeObject:anEmployee];
- 각 managed object context는 undo manager를 유지한다.
- Undo 비활성화
[context processPendingChanges]; // Flush operations for which you want undos
[[context undoManager] disableUndoRegistration];
// Make changes for which undo operations are not to be recorded
// ...
[context processPendingChanges]; // Flush operations for which you do not want undos
[[context undoManager] enableUndoRegistration];
[[<#A managed object#> entity] managedObjectModel];
NSManagedObjectContext *context = [self managedObjectContext];
NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Employee"
inManagedObjectContext:context];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entityDescription];
NSNumber *minimumSalary = ...;
NSPredicate *predicate = [NSPredicate predicateWithFormat:
@"(lastName LIKE[c] 'Worsley') AND (salary > %@)", minimumSalary];
[request setPredicate:predicate];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"firstName" ascending:YES];
[request setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];
[sortDescriptor release];
NSError *error = nil;
NSArray *array = [context executeFetchRequest:request error:&error];
[request release];
NSManagedObjectModel *model = <#Get a model#>;
NSFetchRequest *requestTemplate = [[NSFetchRequest alloc] init];
NSEntityDescription *publicationEntity = [[model entitiesByName] objectForKey:@"Publication"];
[requestTemplate setEntity:publicationEntity];
NSPredicate *predicateTemplate = [NSPredicate predicateWithFormat:
@"(mainAuthor.firstName like[cd] $FIRST_NAME) AND \
(mainAuthor.lastname like[cd] $LST_NAME) AND \
(publicationDate > $DATE)"];
[requestTemplate setPredicate:predicateTemplate];
[model setFetchRequestTemplate:requestTemplate forName:@"PublicationsForAuthorSinceDate"];
[requestTemplate release];
NSError *error = nil;
NSDictionary *substitutionDictionary = [NSDictionary dictionaryWithObjectsAndKeys:
@"Fiona", @"FIRST_NAME",
@"Verde", @"LAST_NAME",
[NSDate dateWithTimeIntervalSinceNow:-31356000], @"DATE",
nil];
NSFetchRequest *fetchRequest = [model fetchRequestFromTemplateWithName:@"PubliccationsForAuthorSinceDate"
substitutionVariables:substitutionDictionary];
NSManagedObjectContext *context = <#Get a managed object context#>;
NSArray *results = [context executeFetchRequest:fetchRequest error:&error];
NSManagedObjectContext *context = [self managedObjectContext];
NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Employee"
inManagedObjectContext:context];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entityDescription];
[request release];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"self == %@", targetObject];
[request setPredicate:predicate];
NSError *error = nil;
NSArray *array = [context executeFetchRequest:request error:&error];
