RestKit-应用启动之间的数据不持久

Question

In my RestKit application, I need to store an email and password in CoreData (I know about NSUserDefaults, but I have other user properties I need stored in CoreData as well).

NSManagedObjectContext *context = [RKManagedObjectStore defaultStore].mainQueueManagedObjectContext;
NSError *error = nil;
NSEntityDescription *userEntity = [NSEntityDescription
                                   entityForName:@"User" inManagedObjectContext:context];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:userEntity];
NSArray *users = [context executeFetchRequest:request error:&error];
return (User *)[users firstObject];

This user object is always null at the application launch.

Then, when the user enters his/her information, I save it like so:

- (void)cacheEmailAndPassword:(NSDictionary *)credentials {

NSManagedObjectContext *context = [RKManagedObjectStore defaultStore].mainQueueManagedObjectContext;

NSError *error = nil;
NSEntityDescription *userEntity = [NSEntityDescription
                                   entityForName:@"User" inManagedObjectContext:context];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:userEntity];
NSArray *users = [context executeFetchRequest:request error:&error]; //should be a single object array for now
User *user = (User *)[users firstObject];

user.email = [credentials objectForKey:@"email"];
user.password = [credentials objectForKey:@"password"];
}

Afterwards, when I try to get the User data from the first function, it returns with all the information. However, when I relaunch the program, the data is null again. Why is this data not persisting between application launches?

EDIT: In case I screwed something up in my initialization, I've pasted it below:

NSError *error = nil;
NSURL *modelURL = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"Model" ofType:@"momd"]];
// NOTE: Due to an iOS 5 bug, the managed object model returned is immutable.
NSManagedObjectModel *managedObjectModel = [[[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL] mutableCopy];
RKManagedObjectStore *managedObjectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:managedObjectModel];

// Initialize the Core Data stack
[managedObjectStore createPersistentStoreCoordinator];

// Configure the object manager
RKObjectManager *objectManager = [RKObjectManager managerWithBaseURL:[NSURL URLWithString:BASE_URL]];
objectManager.managedObjectStore = managedObjectStore;

NSPersistentStore __unused *persistentStore = [managedObjectStore addInMemoryPersistentStore:&error];
NSAssert(persistentStore, @"Failed to add persistent store: %@", error);

[managedObjectStore createManagedObjectContexts];

// Set the default store shared instance
[RKManagedObjectStore setDefaultStore:managedObjectStore];



[RKObjectManager setSharedManager:objectManager];

Answer 1

This is how to add persistent storage

NSURL *modelURL = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"storage" ofType:@"momd"]];
// NOTE: Due to an iOS 5 bug, the managed object model returned is immutable.
NSManagedObjectModel *managedObjectModel = [[[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL] mutableCopy];
RKManagedObjectStore *managedObjectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:managedObjectModel];

BOOL success = RKEnsureDirectoryExistsAtPath(RKApplicationDataDirectory(), &error);
if (! success) {
    RKLogError(@"Failed to create Application Data Directory at path '%@': %@", RKApplicationDataDirectory(), error);
}
NSString *path = [RKApplicationDataDirectory() stringByAppendingPathComponent:@"MyStore.sqlite"];
NSPersistentStore *persistentStore = [managedObjectStore addSQLitePersistentStoreAtPath:path fromSeedDatabaseAtPath:nil withConfiguration:nil options:nil error:&error];
if (! persistentStore) {
    RKLogError(@"Failed adding persistent store at path '%@': %@", path, error);
}

And whenever you are done with the changes, dont forget to save

if(![self.managedObjectContext saveToPersistentStore:&error]){

Answer 2

You never create a user anywhere in the code you posted. You first fetch all users - and none come back. Then you fetch them again - why do you expect that there is one now? Did you check if the user is nil the second time as well?

What you need to to is to insert a new User object if there is none:

User *user = [NSEntityDescription insertNewObjectForEntityForName:@"User" 
             inManagedObjectContext:context];

// configure the user
[context save:nil];