问题
I am working on a CloudKit backed app with a Users record type that has a "following" reference list attribute. I am trying to construct a query to get every user that is following a specified user (i.e. those users in which the specified user appears as an entry in the following reference list).
I am currently trying to construct my NSPredicate for the CKQuery as such:
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"%@ IN following", [[CKReference alloc] initWithRecordID:currentUserID action:CKReferenceActionNone]];
CKQuery *query = [[CKQuery alloc] initWithRecordType:UserRecordType predicate:predicate];
And CloudKit returns the following error message:
"Unknown Item" (11/2003); server message = "did not find required record type";
I feel I might be missing something pretty straight forward in my predicate. Any help would be greatly appreciated!
回答1:
Use CONTAINS operator to test list membership:
CKReference* recordToMatch = [[CKReference alloc] initWithRecordID:currentUserID action:CKReferenceActionNone];
NSPredicate* predicate = [NSPredicate predicateWithFormat:@"following CONTAINS %@", recordToMatch];
If you want to query for more than 1 reference, then you need to use a compound predicate with AND predicate type for each reference in list.
回答2:
Error 11 means that the query cannot find any items in your container matching your record type. In your case UserRecordType type records do not exist in Cloud Kit. You can create a sample schema for that type and the query will work after that.
来源：https://stackoverflow.com/questions/25189158/cloudkit-nspredicate-for-finding-all-records-that-contain-specified-ckreferenc