我找不到一种方法来使用NSPredicate字符串获取数组中的第 n 项。例如：

//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;
}