UIString排序

   排序 只适用于NSString
NSMutableArray *ary = [@[] mutableCopy];
    int i = 10;
    while (i >= 0) {
        i --;
        [ary addObject:[NSString stringWithFormat:@"%d", arc4random()%20]];
    }
    
    [ary sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
        return [obj1  localizedStandardCompare:obj2];
    }];