NSPredicate on array of arrays

Question

I have an array, that when printed out looks like this:

(
        (
        databaseVersion,
        13
    ),
        (
        lockedSetId,
        100
    )
)

Would it be possible to filter this using an NSPredicate (potentially by the index in the array). So something like: give me all rows where element 0 is 'databaseVersion'? I know that if I had an array of dictionaries I could do this with a predicate similar the one found here, but I found that when using dictionaries and storing a large amount of data, my memory consumption went up (from ~80mb to ~120mb), so if possible I would to keep the array. Any suggestions on how this might be done?

Martin R · Accepted Answer · 2012-12-07 17:26:31Z

7

This can be done using "SELF[index]" in the predicate:

NSArray *array = @[
    @[@"databaseVersion", @13],
    @[@"lockedSetId", @100],
    @[@"databaseVersion", @55],
    @[@"foo", @"bar"]
];

NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF[0] == %@", @"databaseVersion"];
NSArray *filtered = [array filteredArrayUsingPredicate:pred];
NSLog(@"%@", filtered);

Output:

(
        (
        databaseVersion,
        13
    ),
        (
        databaseVersion,
        55
    )
)

Or you can use a block-based predicate:

NSPredicate *pred = [NSPredicate predicateWithBlock:^BOOL(NSArray *elem, NSDictionary *bindings) {
    return [elem[0] isEqualTo:@"databaseVersion"];
}];

answered Dec 7, 2012 at 17:26

Martin R

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2 Comments

Kyle Over a year ago

Ah very nice. That does exactly what i'm looking for. Just curious where you came up with the SELF[index] value. I'm not seeing that anywhere in the documentation?

Dave DeLong Over a year ago

@Zenox it's defined in the BNF for predicate format strings: developer.apple.com/library/mac/documentation/cocoa/conceptual/…

Vvk · Accepted Answer · 2015-11-18 11:39:29Z

6

Simply you can use ANY in NSPredicate:

it's works fine

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ANY SELF == %@", @"value"];

or

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ANY SELF contains[cd] %@", @"value"];

answered Nov 18, 2015 at 11:39

Vvk

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