Question

我有Books和Bundles的核心数据结构。一本书可以属于一个或多个包，因此，我在两者之间具有多对多属性。在这本书中，这个属性是从Bunle中调用的。

我为每个实体提供课程。这个类写的时候是多对多的，我只有一对多的关系...所以，那时，来自邦德并不是一个NSSet。我的问题是这个，我必须构建一个可以查看fromBundle NSSet的谓词，看看该集合是否包含我正在寻找的包。

这是我在更改之前的代码。

Bundle *aBundle = [Bundle bundleComNumber:aNumber  inManagedObjectContext:context];


NSArray *all = nil;

NSFetchRequest *request = [[NSFetchRequest alloc] init];

request.entity = [NSEntityDescription entityForName:@"Book" inManagedObjectContext:context];

// the problem is on the next line... as I see, the line is not looking inside the NSSet
// I may be wrong, but when I run this, it crashes and stops on the executeFetchRequest line
// saying **to-many key not allowed here**

request.predicate = [NSPredicate predicateWithFormat:
                     @"(fromBundle == %@)", aBundle];


[request setResultType:NSDictionaryResultType];
[request setReturnsDistinctResults:YES];
[request setPropertiesToFetch:[NSArray arrayWithObjects: @"Name", @"Number", nil]];


NSSortDescriptor *sortByItem =  [NSSortDescriptor sortDescriptorWithKey:ordem ascending:YES selector:@selector(compare:)];
NSArray *sortDescriptors = [NSArray arrayWithObject:sortByItem];
[request setSortDescriptors:sortDescriptors];



NSError *error = nil;
all = [context executeFetchRequest:request error:&error];  // it is crashing here saying **to-many key not allowed here**
[request release];

return all;

我错过了什么？感谢

Answer 1

您是否尝试使用类似@"%@ IN fromBundle"的谓词？

iPhone - 核心数据检查fetch内的NSSet属性

1 个答案: