#import <CoreData/CoreData.h>

@property ( strong , nonatomic) NSManagedObjectContext * coreDataContext;
@property ( strong , nonatomic) NSManagedObjectModel *   coreDataModel;
@property ( strong , nonatomic) NSPersistentStoreCoordinator  * coreDataPersistent;

-(NSManagedObjectModel *) coreDataModel
{if (_coreDataModel ==nil ) {_coreDataModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:[[NSBundle mainBundle] URLForResource:@"resultsModel" withExtension:@"momd"]];}return _coreDataModel;
}
-(NSPersistentStoreCoordinator  *)coreDataPersistent
{if (_coreDataPersistent==nil) {_coreDataPersistent = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self coreDataModel]];NSString * path = [NSSearchPathForDirectoriesInDomains(NSDocumentationDirectory, NSUserDomainMask, YES) lastObject];NSURL * pathURL = [NSURL  fileURLWithPath:[path stringByAppendingString:@"resultsModel.sqlite" ]];NSError * error = nil;NSPersistentStore * store = [ _coreDataPersistent  addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:pathURL options:nil error:&error] ;if (!store) {[NSException raise:@"add database error" format:@"%@" ,[error localizedDescription]];}}return _coreDataPersistent ;
}-(NSManagedObjectContext *) coreDataContext
{if(_coreDataContext ==nil){_coreDataContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];[_coreDataContext setPersistentStoreCoordinator:[self coreDataPersistent]];}return _coreDataContext;
}

 Results * insertResult = [NSEntityDescription insertNewObjectForEntityForName:@"Results" inManagedObjectContext: [self  coreDataContext]];insertResult.in = @"123";insertResult.re = @"ok";insertResult.reD = @"1";NSDateFormatter * dateFormatter = [[NSDateFormatter alloc] init];[dateFormatter setDateFormat:@"YYYY-MM-dd hh:mm:ss"];insertResult.Time = [dateFormatter stringFromDate:[NSDate date]];NSError * error = nil;if(![[self coreDataContext] save: &error]){[NSException raise:@"save data to database error:" format:@"%@",[error localizedDescription]];}

 NSFetchRequest * databaseFecth = [[NSFetchRequest alloc] init];databaseFecth.entity = [NSEntityDescription entityForName:@"Results" inManagedObjectContext:[self coreDataContext]];NSArray * objs = [[self coreDataContext] executeFetchRequest:databaseFecth error:&error];if(error){[NSException raise:@"fetch data from database error:" format:@"%@",[error localizedDescription]];}for (NSManagedObject * obj in objs) {NSLog(@"%@", obj);}

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+entityForName: nil is not a legal NSManagedObjectContext parameter searching for entity name 'Results''