Generic methods for fetching rows from table using Core Data.

gistfile1.m

- (NSArray *)fetchRecordsForEntity:(NSString *)entityName
{
    return [self fetchRecordsForEntity:entityName orderBy:nil];
}

- (NSArray *)fetchRecordsForEntity:(NSString *)entityName orderBy:(NSString *)column
{
    NSError *error = nil;
    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
    
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    
    [request setEntity:[NSEntityDescription entityForName:entityName inManagedObjectContext:managedObjectContext]];
    if (column != nil) {
        [request setSortDescriptors:[NSArray arrayWithObjects:
                                     [NSSortDescriptor sortDescriptorWithKey:column ascending:YES],
                                     nil]];
    }
    
    NSArray *results = [managedObjectContext executeFetchRequest:request error:&error];
    [request release];
    
    if (error != nil) {
        NSLog(@"Error fetching data: %@", [error localizedDescription]);
    }
    return results;
}

- (NSArray *)fetchRecordsForEntity:(NSString *)entityName havingValue:(id)value forColumn:(NSString *)column
{
    NSError *error = nil;
    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
    
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setEntity:[NSEntityDescription entityForName:entityName inManagedObjectContext:managedObjectContext]];
    NSString *predicateFormat = [NSString stringWithFormat:@"%@ == %%@", column];
    [request setPredicate:[NSPredicate predicateWithFormat:predicateFormat, value]];
    
    NSArray *results = [managedObjectContext executeFetchRequest:request error:&error];
    [request release];
    
    if (error != nil) {
        NSLog(@"Error fetching data: %@", [error localizedDescription]);
    }
    
    return results;
}

- (NSArray *)fetchRecordsForEntity:(NSString *)entityName havingValuesForKeys:(NSDictionary *)valuesForKeys
{
    NSError *error = nil;
    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
    
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setEntity:[NSEntityDescription entityForName:entityName inManagedObjectContext:managedObjectContext]];
    
    NSMutableArray *subpredicates = [NSMutableArray array];
    [valuesForKeys enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
        NSString *predicateFormat = [NSString stringWithFormat:@"%@ == %%@", key];
        NSPredicate *subpredicate = [NSPredicate predicateWithFormat:predicateFormat, obj];
        [subpredicates addObject:subpredicate];
    }];
    [request setPredicate:[NSCompoundPredicate andPredicateWithSubpredicates:subpredicates]];
    
    NSArray *results = [managedObjectContext executeFetchRequest:request error:&error];
    [request release];
    
    if (error != nil) {
        NSLog(@"Error fetching data: %@", [error localizedDescription]);
    }
    
    return results;
}

- (NSManagedObject *)fetchRecordForEntity:(NSString *)entityName havingValue:(id)value forColumn:(NSString *)column
{
    NSError *error = nil;
    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
    
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setEntity:[NSEntityDescription entityForName:entityName inManagedObjectContext:managedObjectContext]];
    NSString *predicateFormat = [NSString stringWithFormat:@"%@ == %%@", column];
    [request setPredicate:[NSPredicate predicateWithFormat:predicateFormat, value]];
    NSArray *results = [managedObjectContext executeFetchRequest:request error:&error];
    [request release];
    
    if (error != nil) {
        NSLog(@"Error fetching data: %@", [error localizedDescription]);
    }
    
    if ([results count] > 0) {
        return [results objectAtIndex:0];
    } else {
        return nil;
    }
}

- (NSManagedObject *)fetchRecordForEntity:(NSString *)entityName havingValuesForKeys:(NSDictionary *)valuesForKeys
{
    NSError *error = nil;
    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
    
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setEntity:[NSEntityDescription entityForName:entityName inManagedObjectContext:managedObjectContext]];
    
    NSMutableArray *subpredicates = [NSMutableArray array];
    [valuesForKeys enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
        NSString *predicateFormat = [NSString stringWithFormat:@"%@ == %%@", key];
        NSPredicate *subpredicate = [NSPredicate predicateWithFormat:predicateFormat, obj];
        [subpredicates addObject:subpredicate];
    }];
    [request setPredicate:[NSCompoundPredicate andPredicateWithSubpredicates:subpredicates]];
    
    NSArray *results = [managedObjectContext executeFetchRequest:request error:&error];
    [request release];
    
    if (error != nil) {
        NSLog(@"Error fetching data: %@", [error localizedDescription]);
    }
    
    if ([results count] > 0) {
        return [results objectAtIndex:0];
    } else {
        return nil;
    }
}

- (NSUInteger)countRecordsForEntity:(NSString *)entityName
{
    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
    
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setEntity:[NSEntityDescription entityForName:entityName inManagedObjectContext:managedObjectContext]];
    [request setIncludesSubentities:NO]; //Omit subentities. Default is YES (i.e. include subentities)
    
    NSError *err;
    NSUInteger count = [managedObjectContext countForFetchRequest:request error:&err];
    if (count == NSNotFound) {
        count = 0;
    }
    
    [request release];
    
    return count;
}

- (NSUInteger)countRecordsForEntity:(NSString *)entityName havingValue:(id)value forColumn:(NSString *)column
{
    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
    
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setEntity:[NSEntityDescription entityForName:entityName inManagedObjectContext:managedObjectContext]];
    [request setIncludesSubentities:NO]; //Omit subentities. Default is YES (i.e. include subentities)
    NSString *predicateFormat = [NSString stringWithFormat:@"%@ == %%@", column];
    [request setPredicate:[NSPredicate predicateWithFormat:predicateFormat, value]];
    
    NSError *err;
    NSUInteger count = [managedObjectContext countForFetchRequest:request error:&err];
    if (count == NSNotFound) {
        count = 0;
    }
    
    [request release];
    
    return count;    
}

- (void)deleteRecord:(NSManagedObject *)record
{
    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
    [managedObjectContext deleteObject:record];
}