NSPredicate String to get n'th item in array - ios

Question

I cannot find a way to get the nth item in an array using an NSPredicate string. For example:
//You cannot touch or modify the code inside this method. You can only use the predicate string param to filter the array.
- (NSArray *)filterUsingNSPredicate:(NSString *)PredicateString
{
NSArray *array = #[
#"firstItem",
#"secondItem",
#"thirdItem",
#"fourthItem",
];
NSPredicate *pred = [NSPredicate predicateWithFormat:PredicateString];
NSArray *filtered = [array filteredArrayUsingPredicate:pred];
NSLog(#"This is the second item in the array! %#",filtered); //Thats the only thing in the array.
return filtered;
}

Answer 1

If you want to get an item, you don't receive an NSArray, because you will only receive an object.
You can use NSPredicate to search by name of an object in your array. But what you say, that is not what you want.
You can use [array objectAtIndex:index];, that returns the object in the position you indicate in index.
If you want the index of an object, you can use [array indexOfObject:object];, that returns the index of the object.

Answer 2

Predicates don't know about array indexes. They only know about the single object that they're presented with at any one time, and whether that object makes the predicate true or false.
The way you're presenting this problem in the comments makes absolutely no sense. If you can get a filtered version of the array, then you can get the array. Here's how you use the method you show to do so:
NSArray * fullList = [theAPI filterUsingNSPredicate:#"TRUEPREDICATE"];
TRUEPREDICATE is a special value for predicate strings that always evaluates to true. When you filter an array with that predicate, the result will be identical to the original.
You now have a reference to the array, and can index into it as you would normally.

Answer 3

You can create predicate with block https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSPredicate_Class/#//apple_ref/occ/clm/NSPredicate/predicateWithBlock%3A like this to get 6-th element (at index 5 counting from 0):
__block NSInteger index = 0;
NSPredicate *pred = [NSPredicate predicateWithBlock:^BOOL(id evaluatedObject, NSDictionary<NSString *, id> *bindings)(
return index++ == 5;
)];