C++ Add string to const char* array

Question

Hey so this is probably a dumb beginner question.

I want to write the filename of all .txt files from a folder inside a const char* array[].

So I tried to do it like this:

const char* locations[] = {"1"};
bool x = true;
int i = 0;    

LPCSTR file = "C:/Folder/*.txt";
WIN32_FIND_DATA FindFileData;

HANDLE hFind;
hFind = FindFirstFile(file, &FindFileData);
if (hFind != INVALID_HANDLE_VALUE)
{
    do 
    {
        locations.append(FindFileData.cFileName); //Gives an error
        i++;
    }
    while (FindNextFile(hFind, &FindFileData));
    FindClose(hFind);
}
cout << "number of files " << i << endl;

Basically the code should add the Filename of the .txt file to the const char* locations array but it doesn't work using append as it gives me the error: "C++ expression must have class type but it has type ''const char *''"

So how do I do it right?

hey @Brian you want me to use std::vector<std::string> instead? I ll need the const char* locations[] format for an array listbox. how would I convert that? tried it with std::vector<std::string>locations; and locations.push_back(FindFileData.cFileName); now. How can i make that to an array? — Discord Programs
– Discord Programs, Commented Dec 4, 2021 at 21:29
Use a vector. Then locations[ i ].data() will return the char* pointer to the underlying buffer of std::string. — digito_evo
– digito_evo, Commented Dec 4, 2021 at 21:31

Ahmed Shaqanbi · Accepted Answer · 2021-12-04 22:04:18Z

3

Problem:

You can't append items to a C array -T n[]- because the length of the array is determined at compile time.
An array is a pointer(which is a scalar type), which isn't an object and doesn't have methods.

Solution:

The easiest solution is to use an std::vector which is a dynamic array:

#include <vector>
// ...
std::vector<T> name;

// or if you have initial values...
std::vector<T> name = {
    // bla bla bla..
};

In your case an array called location of strings is std::vector<std::string> locations.
For some reason, C++ containers don't like the classical append(), and provide the following methods:

container.push_back();  // append.
container.push_front(); // prepend.
container.pop_back();   // remove last
container.pop_front();  // remove first

Note that std::vector only provides push_back and pop_back

See:

std::vector

edited Dec 4, 2021 at 22:04

answered Dec 4, 2021 at 21:40

Ahmed Shaqanbi

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3 Comments

Peter Over a year ago

An array is not a pointer.

Ahmed Shaqanbi Over a year ago

@Peter An array is a pointer to elements × 1 element size length chunk of memory. Also int a[5]; std::cout << a << std::endl; prints an address.

Peter Over a year ago

An array can be converted to a pointer (to its first element) but is something different. There are contexts when assuming an array is a pointer works, and others where it fails. If what you say is true, the discussion in this link would be moot. stackoverflow.com/questions/1461432/…

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