数组包含字典-根据key排序

NSArray *array = [NSArray array];
    [array sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2){
        NSNumber index1 = [obj1 valueForKey:@"index"];
        NSNumber index2 = [obj2 valueForKey:@"index"];
        return [index1 compare:index2];
    }];