Using NSPredicate to filter an NSArray based on NSDictionary keys

Question

I have an array of dictionaries.

I want to filter the array based on a key.

I tried this:

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(SPORT ==  %@)", @"Football"];

NSArray *filteredArray = [data filteredArrayUsingPredicate:predicate];

This doesn't work, I get no results. I think I'm doing something wrong. I know this is the method if "SPORT" was an ivar. I think it is probably different if it is a key.

I haven't been able to find an example however.

Thanks

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Update

I added quotes around the string I am searching for.

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(SPORT ==  '%@')", @"Football"];

It still does not work.

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Update 2

Solved it. I actually had to remove the single quotes, which seems to go against what the guide says.

My real problem is I had a nested array and I wasn't actually evaluating the dictionaries. Bone head move.

Solution 1

It should work - as long as the data variable is actually an array containing a dictionary with the key SPORT

NSArray *data = [NSArray arrayWithObject:[NSMutableDictionary dictionaryWithObject:@"foo" forKey:@"BAR"]];    
NSArray *filtered = [data filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"(BAR == %@)", @"foo"]];

Filtered in this case contains the dictionary.

(the %@ does not have to be quoted, this is done when NSPredicate creates the object.)

Solution 2

I know it's old news but to add my two cents. By default I use the commands LIKE[cd] rather than just [c]. The [d] compares letters with accent symbols. This works especially well in my Warcraft App where people spell their name "Vòódòó" making it nearly impossible to search for their name in a tableview. The [d] strips their accent symbols during the predicate. So a predicate of @"name LIKE[CD] %@", object.name where object.name == @"voodoo" will return the object containing the name Vòódòó.

From the Apple documentation: like[cd] means “case- and diacritic-insensitive like.”) For a complete description of the string syntax and a list of all the operators available, see Predicate Format String Syntax.

Solution 3

#import <Foundation/Foundation.h>
// clang -framework Foundation Siegfried.m 
    int
main() {
    NSArray *arr = @[
        @{@"1" : @"Fafner"},
        @{@"1" : @"Fasolt"}
    ];
    NSPredicate *p = [NSPredicate predicateWithFormat:
        @"SELF['1'] CONTAINS 'e'"];
    NSArray *res = [arr filteredArrayUsingPredicate:p];
    NSLog(@"Siegfried %@", res);
    return 0;
}

Solution 4

NSPredicate is only available in iPhone 3.0.

You won't notice that until try to run on device.

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