Question

I have a class which parses the Command line arguments and then returns the parsed value to the client class. For parsing, I need to pass argv to parse function. I would like to pass by reference but from what I know , we never use the ‘&’ symbol when passing arrays. Arrays are not objects that can be passed by reference. Here is my code:

#include <iostream>
#include <fstream> 
using namespace std;

class cmdline
{
    const char * ifile;
    public:

    cmdline():ifile(NULL){}

    const char  * const getFile() const
    {
        return (ifile);
    }

    void parse(int argc,const  char** argv)
    {
        //parse and assign value to ifile 
        //  ifile = optarg;
        // optarg is value got from long_getopt

    }
};

int main(int argc, char ** argv)
{
    cmdline CmdLineObj;
    CmdLineObj.parse(argc, const_cast<const char**>(argv));
    const char * const ifile = CmdLineObj.getFile();
    ifstream myfile (ifile);
    return 0;
}

1) Is the way argv is treated, correct?

2) Better way to handle, ifile?

3) I want to return ifile as reference, what change should I do, if needed?

My code works the way it is supposed to work, but the reason I came to SO is to “not-just-make-it-work” but do it properly.

Thanks for your help.

EDIT:: After Mehrdad’s comment, I edited like this:

class CmdLine
{
    const char *  ifile;

public:
    const  char  * & getFile() const
    {
        return (ifile);
    }

But I get the error – invalid initialization of reference of type ‘const char*&’ from expression of type ‘const char’

Answer 1

Arrays are not objects that can be passed by reference.

What makes you think that?

1) Is the way argv is treated, correct?

CmdLineObj.parse(argc, const_cast< const char** >(argv));

Why are you const casting that? Instead of casting, you could change your definition of main to const char** argv.

2) Better way to handle, ifile?

Well, there is always std::string, but since all you seem to do is then pass the value to an std::ifstream I don’t see a point in using it.

3) I want to return ifile as reference, what change should I do, if needed?

What would be the point of returning a pointer as a reference? Are you expecting callers of getFile to actually change the member that points to such string? You shouldn’t be doing that since getFile is a const member function. If you are thinking performance, then returning a reference to a pointer in this case will actually be worse than returning the pointer by value. The string contents are not getting copied when returned from getFile, like they would if ifile was instead an std::string (in which case returning a const reference would make sense).