我有一个独立的 CoreData 实体，其中包含大约 30 条记录。我必须定期删除记录并重新填充相关的 CoreTableViewController。我的 NSFetchRequest 没有返回任何记录。
但是 setupFetchedResultsController 中完全相同的 FetchRequest 确实会返回记录。
我确信我在这里遗漏了一些明显的东西，但还没有弄清楚是什么。有任何想法吗？
- (void)eraseFetchedResults:(NSManagedObjectContext *)myContext
{
NSFetchRequest *allAthletes = [NSFetchRequest fetchRequestWithEntityName:@"ResultsForAthleteSearch"];
allAthletes.sortDescriptors = [NSArray arrayWithObject:[
NSSortDescriptor sortDescriptorWithKey:@"orderRecordsDownloaded"
ascending:YES]];
// no predicate because we want ALL the Athletes
[allAthletes setIncludesPropertyValues:YES]; //only fetch the managedObjectID
NSError * error = nil;
NSArray * athletes = [myContext executeFetchRequest:allAthletes error:&error];
NSLog(@"NSArray athletes is %d", [athletes count]);
//error handling goes here
for (NSManagedObject * athlete in athletes) {
[myContext deleteObject:athlete];
}
NSError *saveError = nil;
[myContext save:&saveError];
}
- (void)setupFetchedResultsController // attaches an NSFetchRequest to this UITableViewController
{
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"ResultsForAthleteSearch"];
request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"orderRecordsDownloaded" ascending:YES]];
// no predicate because we want ALL the Athletes
self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request
managedObjectContext:self.athleteSearchDatabase.managedObjectContext
sectionNameKeyPath:nil
cacheName:nil];
}
下面是调用方法：
- (void)useDocument
{
NSLog(@"Does athleteSearchDatabase exist? %d", [[NSFileManager defaultManager] fileExistsAtPath:[self.athleteSearchDatabase.fileURL path]]);
NSString *checkName = _searchName;
if (![[NSFileManager defaultManager] fileExistsAtPath:[self.athleteSearchDatabase.fileURL path]]) {
// does not exist on disk, so create it
[self.athleteSearchDatabase saveToURL:self.athleteSearchDatabase.fileURL forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success) {
[self setupFetchedResultsController];
NSLog(@"checkName is %@ before calling fetchAthleteSearchResultsIntoDocument.",checkName);
[self fetchAthleteSearchResultsIntoDocument:self.athleteSearchDatabase whereNameIs:checkName];
}];
} else if (self.athleteSearchDatabase.documentState == UIDocumentStateClosed) {
// exists on disk, but we need to open it
[self eraseFetchedResults:self.athleteSearchDatabase.managedObjectContext];
[self.athleteSearchDatabase openWithCompletionHandler:^(BOOL success) {
[self setupFetchedResultsController];
[self fetchAthleteSearchResultsIntoDocument:self.athleteSearchDatabase whereNameIs:checkName];
}];
} else if (self.athleteSearchDatabase.documentState == UIDocumentStateNormal) {
// already open and ready to use
[self setupFetchedResultsController];
}
}