objective-c - 核心数据数据库为空测试

Question

如何测试核心数据数据库是否为空？我试过:

NSIndexPath *path1 = [NSIndexPath indexPathForRow:0 inSection:0];
NSManagedObject *managedObject = [self.fetchedResultsController objectAtIndexPath:path1];
if([[managedObject valueForKey:@"date"] description]!=nil){SOMEFUNCTION}else{SOMEFUNCTION}

谢谢

Answer 1

您必须为您在核心数据中使用的每个实体创建一个获取请求。如果 fetchrequest 没有返回结果，则说明您的核心数据中没有存储此实体的对象。

- (BOOL)coreDataHasEntriesForEntityName:(NSString *)entityName {
    NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
    NSEntityDescription *entity = [NSEntityDescription entityForName:entityName inManagedObjectContext:self.managedObjectContext];
    [request setEntity:entity];
    [request setFetchLimit:1];
    NSError *error = nil;
    NSArray *results = [self.managedObjectContext executeFetchRequest:request error:&error];
    if (!results) {
        LogError(@"Fetch error: %@", error);
        abort();
    }
    if ([results count] == 0) {
        return NO;
    }
    return YES;
}