我有两个实体名为“Category”和“Article”,它们之间存在多对多的关系。我想形成一个谓词,搜索所有分类名称等于某个值的文章。我有以下代码:
NSEntityDescription *entityArticle = [NSEntityDescription entityForName:@"Article" inManagedObjectContext:managedObjectContext];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"title" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"categories.name == [cd] %@", category.name];
[request setSortDescriptors:sortDescriptors];
[request setEntity:entityArticle];
[request setPredicate:predicate];
NSMutableArray *results = [[managedObjectContext executeFetchRequest:request error:nil] mutableCopy];
if ([results count] > 0)
NSLog(@"Results found.");
else
NSLog(@"NO results found.");
[request release];
[sortDescriptor release];
[sortDescriptors release];
我收到的错误是 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'to-many key not allowed here'
是否有任何选项可以检索所需的数据?