Question

I am trying to make a pointer to fstream so I can use it in all of my class methods :

class P
{
    private:
        fstream *fs;

    public:
        P()
        {
            fstream fs(filepath, openmode);
            this->fs = &fs;
        }
};

But it seem to be not pointing to it at all e.g if I write:

fs->is_open() 

it will return false, whereas if I write:

fs.is_open()

it will return true.

What is causing this? I also tried to change the pointer to another like fstr but that didn’t work either.

Answer 1

To accomplish what you are asking for, you need to use the new operator, like this:

SmartIO::SmartIO(const char * filepath , Mode mode)
    : fs(NULL), buffer(NULL), offset(0)
{
    switch (mode)
    {
        case Mode::inText:
        {
            fs = new fstream(filepath,fstream::in|fstream::ate);
            break;
        }
        case Mode::inBinary:
        {
            fs = new fstream(filepath,fstream::in|fstream::binary|fstream::ate);
            break;
        }
    }

    if ((fs) && (fs->is_open()))
    {
        buffer = new std:vector<char>(fs->tellg(), 0);
        fs->seekg(0, ios::beg);
        fs->read(buffer->data(), buffer->size());
    }
    else
    {
        printf( "cant open the file!");
    }
}

SmartIO::~SmartIO()
{
    delete fs;
    delete buffer;
}