ios - NSPredicate filter array within object within array

Question

I have the following method:

- (NSMutableArray *)getFilteredArrayFromArray:(NSMutableArray *)array withText:(NSString *)text {

if ([array count] <= 0)
    return nil;

NSMutableArray *arrayToFilter = [NSMutableArray arrayWithArray:array];
NSString *nameformatString = [NSString stringWithFormat:@"stationName contains[c] '%@'", text];
NSPredicate *namePredicate = [NSPredicate predicateWithFormat:nameformatString];

NSString *descformatString = [NSString stringWithFormat:@"stationTagline contains[c] '%@'", text];
NSPredicate *descPredicate = [NSPredicate predicateWithFormat:descformatString];

NSString *aToZformatString = [NSString stringWithFormat:@"stationSearchData.browseAtozArray.city contains[c] '%@'", text];
NSPredicate *aToZPredicate = [NSPredicate predicateWithFormat:aToZformatString];

NSPredicate * combinePredicate = [NSCompoundPredicate orPredicateWithSubpredicates:[NSArray arrayWithObjects:namePredicate, descPredicate, aToZPredicate, nil]];

[arrayToFilter filterUsingPredicate:combinePredicate];

return arrayToFilter;
}

The first 2 predicates work fine. But the last one (aToZPredicate), is not working. stationSearchData is a StationSearchData object, and browseAtozArray is an NSMutableArray.

How can I use a predicate to essentially search an array within an array within an array?

Here is the interface for the StationSearchData object:

@interface StationSearchData : NSObject

@property (nonatomic, strong) NSString *location;
@property (nonatomic, strong) NSString *city;
@property (nonatomic, strong) NSString *latitude;
@property (nonatomic, strong) NSString *longitude;

@property (nonatomic, strong) NSMutableArray *browseAtozArray;
@property (nonatomic, strong) NSMutableArray *genreArray;

@end

Thanks!

Answer 1

First of all, you should not use stringWithFormat to build predicates. This can cause problems if the search text contains any special characters like ' or ". So you should replace

NSString *nameformatString = [NSString stringWithFormat:@"stationName contains[c] '%@'", text];
NSPredicate *namePredicate = [NSPredicate predicateWithFormat:nameformatString];

by

NSPredicate *namePredicate = [NSPredicate predicateWithFormat:@"stationName contains[c] %@", text];

To search within an array, you have to use "ANY" in the predicate:

NSPredicate *aToZPredicate =
  [NSPredicate predicateWithFormat:@"ANY stationSearchData.browseAtozArray.city CONTAINS[c] %@", text];