NSPredicate for property of object in NSArray of NSArray - ios

Question

I have an objects like the below structure: Transaction has an array of Items. Item has an array of SubItems
#interface Transaction : NSObject
#property (nonatomic, copy) NSString *id;
#property (nonatomic, assign) NSInteger status;
#property (nonatomic, strong) NSArray *items; // array of Item
#end
#interface Item : NSObject
#property (nonatomic, copy) NSString *identifier;
#property (nonatomic, assign) NSInteger price;
#property (nonatomic, strong) NSArray *subitems;
#end
#interface SubItem : NSObject
#property (nonatomic, copy) NSString *name;
#property (nonatomic, assign) NSInteger price;
#end
I would like to create predicate to find name and price of Subitem from NSArray of Transaction
pred = [NSPredicate predicateWithFormat:
#"ANY SELF.%K.%K.%K contains %#",
#"items",
#"subitems",
#"name",
#"MY_SUB_ITEM_NAME"];
This generates the error below.
failed: caught "NSInvalidArgumentException", "Can't do regex matching
on object (
MY_SUB_ITEM_NAME )."
However when I use the similar format to find out properties in Transaction. It works fine.
pred = [NSPredicate predicateWithFormat:
#"SELF.%K LIKE %#",
#"identifier",
#"TX001"];
How should I correct my predicate to query property in Item and SubItem

Answer 1

I think that cannot work with -predicateWithFormat: for two aggregation levels. On each level you can have a ANY or an ALL aggregation. So the "right" syntax would be ANY items ANY subitems.… = …. Or ANY items ALL subitems.…= …" or …
You can try to build the predicate manually with NSExpression, probably using subqueries.
Oh, you are not using Core Data, what I assumed. So simply do it manually in a loop or use a computed property.