error: request for member is of non-class type string & char

Question

this is my Node Structure;

class Node
{
public:
    string data;
    Node *next;
    Node *child;
};
Node *
createList(string *arr, int n)
{
    Node *head = NULL;
    Node *tmp;

    for (int i = 0; i < n; i++)
    {
        if (head == NULL)
        {
            tmp = head = new Node();
        }
        else
        {
            tmp->next = new Node();
            tmp = tmp->next;
        }

        tmp->data = arr[i];
        tmp->next = tmp->child = NULL;
    }
    return head;
}

This is the problem where I get.

    filesystem::path cwd = filesystem::current_path();
    int file_count;
    vector files = filesInDir(cwd, file_count);

    string file_names[file_count];
    string file_extensions[file_count];
    string file_sizes[file_count];

    for (int i = 0; i < file_count; ++i)
    {
        for (int i = 0; i < file_count; ++i)
        {
            file_names.push_back(files[i + 0 * file_count]);
            file_extensions.push_back(files[i + 1 * file_count]);
            file_sizes.push_back(files[i + 2 * file_count]);
        }
    }

    Node *head1 = createList(file_names, file_count);
    Node *head2 = createList(file_extensions, file_count);
    Node *head3 = createList(file_sizes, file_count);

main.cpp:54:24: error: request for member 'push_back' in 'file_names', which is of non-class type 'std::string [file_count]' {aka 'std::__cxx11::basic_string<char> [file_count]'}
   54 |             file_names.push_back(files[i + 0 * file_count]);
      |                        ^~~~~~~~~

I'm trying to read all files in the current directory, and save them into like vector((file_name_1, file_extension_1, file_size_1), ......)(All of them in the string format). I need to use multi linked list to store them, how can I solve the problem?

Answer 1

push_back() is a method of standard C++ containers, like std::vector. But you are trying to call it on C-style variable-length arrays instead, which do not have methods (and BTW, they are NOT part of standard C++).

Since you are already using std::vector anyway for the return value of filesInDir(), simply use std::vector<std::string> instead of std::string[] for your variable-length arrays, eg:

vector<string> file_names;
file_names.reserve(file_count);

// populate file_names as needed ...

Node *head1 = createList(file_names.data(), file_names.size());
...

Do the same with the file_extensions and file_sizes arrays, too.

---

Also, since you are using the standard library anyway (for std::string, std::vector, and std::filesystem), consider using std::list (double-linked) or std::forward_list (single-linked) for the linked lists, instead of using a manual implementation.

Answer 2

I solved it with;

for (int i = 0; i < file_count; ++i)
    {
        for (int i = 0; i < file_count; ++i)
        {
            file_names[i] = (files[i + 0 * file_count]);
            file_extensions[i] = (files[i + 1 * file_count]);
            file_sizes[i] = (files[i + 2 * file_count]);
        }
    }

but this time I needed to add tail pointer to node structure, I'm trying to solve that

class Node
{
public:
    string data;
    Node *next;
    Node *child;
};

Node *
createList(string *arr, int n)
{
    Node *head = NULL;
    Node *tmp;

    for (int i = 0; i < n; i++)
    {
        if (head == NULL)
        {
            tmp = head = new Node();
        }
        else
        {
            tmp->next = new Node();
            tmp = tmp->next;
        }

        tmp->data = arr[i];
        tmp->next = tmp->child = NULL;
    }
    return head;
}