Does a Core Data NSSet contain an object with a certain ID?

问题

I have a Core Data object that contains an NSSet of other objects (e.g. Library object contains NSSet of Books). What's the best way to check if an instance of Library contains a book with a certain bookID?

Is it possible to be done with Key Value coding or do I have to enumerate all books and check them manually?

回答1:

Yes, you can use KVC for this.

BOOL bookExists = [[set valueForKey:@"bookID"] containsObject:@"myBookID"];

来源：https://stackoverflow.com/questions/7256909/does-a-core-data-nsset-contain-an-object-with-a-certain-id