Question

i have a NSArray containing some NSDictionaries which themselves also include a NSDictionary.

NSDictionary *dict1 = [NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:@"cover" forKey:@"type"] forKey:@"image"];
NSDictionary *dict2 = [NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:@"cover" forKey:@"type"] forKey:@"image"];
NSDictionary *dict3 = [NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:@"back" forKey:@"type"] forKey:@"image"];
NSDictionary *dict4 = [NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:@"cover" forKey:@"type"] forKey:@"image"];

NSArray *myArray = [NSArray arrayWithObjects:dict1, dict2, dict3, dict4, nil];

is there a way to filter myArray for all Image-Dictionaries where the type is f.e. “cover” using a NSPredicate?

tried predicates like

predicateWithFormat:@"(SELF.image.type == %@)", @"cover"]

or

predicateWithFormat:@"(image.type == %@)", @"cover"]

but without success.

thanks in advance! leave a comment if something is unclear

// edit

so

NSPredicate *p = [NSPredicate predicateWithFormat:@"image.type == %@", @"cover"];

is working. but in my case i want to sort out size == original. what i did is

NSPredicate *p = [NSPredicate predicateWithFormat:@"image.size == %@", @"original"];

but then my app crashes with

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSSymbolicExpression length]: unrecognized selector sent to instance

and pointing to my filteredArrayUsingPredicate method. i cannot see any difference between type and size. see my NSLog of my Array here

 (
        {
        image =         {
            height = 1500;
            id = 4e5808765e73d607350059b4;
            size = original;
            type = poster;
            url = "someurl";
            width = 1000;
        };
    },
        {
        image =         {
            height = 750;
            id = 4e5808765e73d607350059b4;
            size = mid;
            type = poster;
            url = "someurl";
            width = 500;
        };
    },

anybody knows why it crashes when i try to use size instead of type ?

Answer 1

The following code worked for me:

NSDictionary *dict1 = [NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:@"cover" forKey:@"type"] forKey:@"image"];
NSDictionary *dict2 = [NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:@"cover" forKey:@"type"] forKey:@"image"];
NSDictionary *dict3 = [NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:@"back" forKey:@"type"] forKey:@"image"];
NSDictionary *dict4 = [NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:@"cover" forKey:@"type"] forKey:@"image"];

NSArray *myArray = [NSArray arrayWithObjects:dict1, dict2, dict3, dict4, nil];

NSPredicate *p = [NSPredicate predicateWithFormat:@"image.type == %@", @"cover"];
NSLog(@"%@", [myArray filteredArrayUsingPredicate:p]);