NSPersistentStore Class Reference

Inherits from
Conforms to
Framework
/System/Library/Frameworks/CoreData.framework
Availability
Available in OS X v10.5 and later.
Declared in
NSPersistentStore.h
Companion guides
Related sample code

Overview

This class is the abstract base class for all Core Data persistent stores.

Core Data provides four store types—SQLite, Binary, XML, and In-Memory (the XML store is not available on iOS); these are described in “Persistent Store Features”. Core Data also provides subclasses of NSPersistentStore that you can use to define your own store types: NSAtomicStore and NSIncrementalStore. The Binary and XML stores are examples of atomic stores that inherit functionality from NSAtomicStore.

Subclassing Notes

You should not subclass NSPersistentStore directly. Core Data only supports subclassing of NSAtomicStore and NSIncrementalStore.

The designated initializer is initWithPersistentStoreCoordinator:configurationName:URL:options:. When you implement the initializer, you must ensure you load metadata during initialization and set it using setMetadata:.

You must override these methods:

Tasks

Initializing a Persistent Store

Working with State Information

Managing Metadata

Setup and Teardown

Supporting Migration

Class Methods

metadataForPersistentStoreWithURL:error:

Returns the metadata from the persistent store at the given URL.

+ (NSDictionary *)metadataForPersistentStoreWithURL:(NSURL *)url error:(NSError **)error
Parameters
url

The location of the store.

error

If an error occurs, upon return contains an NSError object that describes the problem.

Return Value

The metadata from the persistent store at url. Returns nil if there is an error.

Special Considerations

Subclasses must override this method.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

migrationManagerClass

Returns the NSMigrationManager class for this store class.

+ (Class)migrationManagerClass
Return Value

The NSMigrationManager class for this store class

Discussion

In a subclass of NSPersistentStore, you can override this to provide a custom migration manager subclass (for example, to take advantage of store-specific functionality to improve migration performance).

Availability
  • Available in OS X v10.6 and later.
Declared In
NSPersistentStore.h

setMetadata:forPersistentStoreWithURL:error:

Sets the metadata for the store at a given URL.

+ (BOOL)setMetadata:(NSDictionary *)metadata forPersistentStoreWithURL:(NSURL *)url error:(NSError **)error
Parameters
metadata

The metadata for the store at url.

url

The location of the store.

error

If an error occurs, upon return contains an NSError object that describes the problem.

Return Value

YES if the metadata was written correctly, otherwise NO.

Special Considerations

Subclasses must override this method to set metadata appropriately.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

Instance Methods

configurationName

Returns the name of the managed object model configuration used to create the receiver.

- (NSString *)configurationName
Return Value

The name of the managed object model configuration used to create the receiver.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

didAddToPersistentStoreCoordinator:

Invoked after the receiver has been added to the persistent store coordinator.

- (void)didAddToPersistentStoreCoordinator:(NSPersistentStoreCoordinator *)coordinator
Parameters
coordinator

The persistent store coordinator to which the receiver was added.

Discussion

The default implementation does nothing. You can override this method in a subclass in order to perform any kind of setup necessary before the load method is invoked.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

identifier

Returns the unique identifier for the receiver.

- (NSString *)identifier
Return Value

The unique identifier for the receiver.

Discussion

The identifier is used as part of the managed object IDs for each object in the store.

Special Considerations

NSPersistentStore provides a default implementation to provide a globally unique identifier for the store instance.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

initWithPersistentStoreCoordinator:configurationName:URL:options:

Returns a store initialized with the given arguments.

- (id)initWithPersistentStoreCoordinator:(NSPersistentStoreCoordinator *)root configurationName:(NSString *)name URL:(NSURL *)url options:(NSDictionary *)options
Parameters
coordinator

A persistent store coordinator.

configurationName

The name of the managed object model configuration to use. Pass nil if you do not want to specify a configuration.

url

The URL of the store to load.

options

A dictionary containing configuration options. See NSPersistentStoreCoordinator for a list of key names for options in this dictionary.

Return Value

A new store object, associated with coordinator, that represents a persistent store at url using the options in options and—if it is not nil—the managed object model configuration configurationName.

Discussion

You must ensure that you load metadata during initialization and set it using setMetadata:.

Special Considerations

This is the designated initializer for persistent stores.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

isReadOnly

Returns a Boolean value that indicates whether the receiver is read-only.

- (BOOL)isReadOnly
Return Value

YES if the receiver is read-only, otherwise NO.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

loadMetadata:

Instructs the receiver to load its metadata.

- (BOOL)loadMetadata:(NSError **)error
Parameters
error

If an error occurs, upon return contains an NSError object that describes the problem.

Return Value

YES if the metadata was loaded correctly, otherwise NO.

Special Considerations

There is no way to return an error if the store is invalid.

Availability
  • Available in OS X v10.6 and later.
Declared In
NSPersistentStore.h

metadata

Returns the metadata for the receiver.

- (NSDictionary *)metadata
Return Value

The metadata for the receiver. The dictionary must include the store type (NSStoreTypeKey) and UUID (NSStoreUUIDKey).

Special Considerations

Subclasses must override this method to provide storage and persistence for the store metadata.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

options

Returns the options with which the receiver was created.

- (NSDictionary *)options
Return Value

The options with which the receiver was created.

Discussion

See NSPersistentStoreCoordinator for a list of key names for options in this dictionary.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

persistentStoreCoordinator

Returns the persistent store coordinator which loaded the receiver.

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
Return Value

The persistent store coordinator which loaded the receiver.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

setIdentifier:

Sets the unique identifier for the receiver.

- (void)setIdentifier:(NSString *)identifier
Parameters
identifier

The unique identifier for the receiver.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

setMetadata:

Sets the metadata for the receiver.

- (void)setMetadata:(NSDictionary *)storeMetadata
Parameters
storeMetadata

The metadata for the receiver.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

setReadOnly:

Sets whether the receiver is read-only.

- (void)setReadOnly:(BOOL)flag
Parameters
flag

YES if the receiver is read-only, otherwise NO.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

setURL:

Sets the URL for the receiver.

- (void)setURL:(NSURL *)url
Parameters
url

The URL for the receiver.

Discussion

To alter the location of a store, send the persistent store coordinator a setURL:forPersistentStore: message.

Availability
  • Available in OS X v10.5 and later.
See Also
Declared In
NSPersistentStore.h

type

Returns the type string of the receiver.

- (NSString *)type
Return Value

The type string of the receiver.

Discussion

This string is used when specifying the type of store to add to a persistent store coordinator.

Special Considerations

Subclasses must override this method to provide a unique type.

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h

URL

Returns the URL for the receiver.

- (NSURL *)URL
Return Value

The URL for the receiver.

Availability
  • Available in OS X v10.5 and later.
See Also
Declared In
NSPersistentStore.h

willRemoveFromPersistentStoreCoordinator:

Invoked before the receiver is removed from the persistent store coordinator.

- (void)willRemoveFromPersistentStoreCoordinator:(NSPersistentStoreCoordinator *)coordinator
Parameters
coordinator

The persistent store coordinator from which the receiver was removed.

Discussion

The default implementation does nothing. You can override this method in a subclass in order to perform any clean-up before the store is removed from the coordinator (and deallocated).

Availability
  • Available in OS X v10.5 and later.
Declared In
NSPersistentStore.h