NSPredicate for property of object in NSArray of NSArray

问题

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

回答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.

来源：https://stackoverflow.com/questions/32263367/nspredicate-for-property-of-object-in-nsarray-of-nsarray

标签

ios

objective-c

regex

nsarray

nspredicate