Passing constant object by reference discards qualifiers error

[browncpp]

Hi All,
I'm hoping someone can help me with this error and what I am doing wrong, I've spent an entire day trying to get to grips with it but concede I need help. Googling and searching the forums returns threads where the code is inconsistent in declaring one part of the code constant and elsewhere not.
I thought that, if I pass a reference to an object into a function and declare it constant, I would still be able to use accessor functions of the object that are constant themselves?

The Hop class below has some accessor functions which are declared constant.

class Hop{
	public:
        Hop();
        ~Hop();
		std::string GetDescription() const {return itsDescription;}
		float GetAA() const {return itsAA;}
		float GetWeight() const {return itsWeight;}
		float GetBoilTime() const {return itsBoilTime;}
		void SetDescription(std::string s) {itsDescription = s;}
		void SetAA(float fAA) {itsAA = fAA;}
		void SetWeight(float fWeight) {itsWeight = fWeight;}
		void SetBoilTime (float fBoilTime) {itsBoilTime = fBoilTime;}
	private:
		std::string itsDescription;
		float itsAA;
		float itsWeight;
		float itsBoilTime;
};

In the main code I use a vector of class hop and load it with details from a text file (code not included)
I have a function 'Hop EnterHoppingDetails(const Hop &myHop)' which I have added the keyword const to make it constant since I am only calling member functions of type constant from the hop reference passed in.
each call to GetDescription(), GetAA(), GetWeight(), GetBoilTime() all generate the compile error

main.cpp:148:49: error: passing ‘const Hop’ as ‘this’ argument of ‘const string Hop::GetDescription()’ discards qualifiers [-fpermissive]
ie the line
cout << "Hop: " << myHop.GetDescription() << endl;

Your help to understand what I have done wrong will be greatly appreciated.

Cheers,
Wayne.

Hop EnterHoppingDetails(const Hop &myHop)
{
// used by Add and Edit a hop before passing back modified hop object
// adjust hop AA, weight, boil time
    string sTemp;
    Hop updatedHop = myHop;
    float fNewAA;
    float fNewWeight;
    float fNewBoilTime;
    bool bValidNumber = true;
// set AA
    do {
        cout << "Hop: " << myHop.GetDescription() << endl;
        cout << "Alpha Acid - return to accept or type new AA: " << myHop.GetAA() << " " ;
        getline(cin, sTemp);
        if (sTemp.length() > 0)
        {
            // New AA entered, cast to float
            bValidNumber = StringToFloat(sTemp, fNewAA);
            if (bValidNumber == true && fNewAA > 0 && fNewAA < 50 )
            {
                updatedHop.SetAA(fNewAA);
            } else
            {
                bValidNumber = false;
            }
        }
    } while (bValidNumber == false);
    cout << "Hop Alpha Acid: " << updatedHop.GetAA() << endl;

[Computergeek01]

I have a feeling that we would have to see more code to diagnose what is actually wrong. You have to be doing something strange somewhere else because I can't even recreate your issue from what I see here. The simple solution would be to pass 'myHop' to this function as a regular reference.

[browncpp]

Hi Computergeek, thank you for taking a look, You got me trying again today and after spending another day I finally found the fault.
I started off writing a small program that I might upload and of course there was no error. So I broke the program down and down until there was nothing left of it, in the end the penny dropped, I had changed the hop class file by adding 'const' to the accessors but did not alter the header file. re-compiling the hop class and then the main file everything compiled fine. Such a newbie. Lesson learned though and so pleased I found the error. Now I can get on with writing some more code!

Cheers,
Wayne.