external resolution errors during linking

[henpecked1]

I have the function below in three base classes, one base, then one derived, and another derived from the second. I'm getting external resolution errors when I try to build it.

virtual void printtostream(ostream& out);

//Since it is a virtual function the above was not defined in any  of the class definitions. 
//My function, right before main, is this

ostream& operator << (ostream &out, telnumber &tn)
{
	tn.printtostream(out);
	return out;
}

This gives me three external resolution errors. What am I forgetting to do?

[Ancient Dragon]

In the base class the function should be declared a pure virtual function virtual void printtostream(ostream& out) = 0; This will force one (or more) of the derived classes to provide the implementation for that function.

[henpecked1]

Okay, I made it a true virtual, but it tells me it can't instantiate the class telnumber (multiple times) because it is now an abstract (which I knew it would be with the =0 added)

So I tried a couple of implementations in the workingnumber.cpp and it's still happening. My very obvious deduction is that either my implementation is horribly wrong, or I"m doing it in the wrong place. I don't think it's the wrong place...and unless I miss my guess, I'll also have to define it in the cpp file for billing number...is that correct?

[Ancient Dragon]

We are just guessing now. Post the code so that we can test see exactly what you have done (you can attach the *.cpp and *.h file(s) to your post)

[henpecked1]

Okay, here are the classes, in order, and in h/cpp order

class telnumber
{
public:
	telnumber();
	telnumber (string i_npa,string i_nxx,string i_line);
	~telnumber();
	void setnpa (string& newnpa);
	void setnxx (string& newnxx);
	void setline (string& newline);
	string getnpa();
	string getnxx();
	string getline();
	virtual void printtostream(ostream& out)=0;

private:
	string npa;
	string nxx;
	string line;

};


telnumber::telnumber()
	{
		npa="";
		nxx="";
		line="";
	}

	telnumber::telnumber (string i_npa,string i_nxx,string i_line)
	{

	}

	void telnumber::setnpa (string& newnpa)
	{
		npa=newnpa;
	}
	
	void telnumber::setnxx (string& newnxx)
	{
		nxx=newnxx;
	}
	
	void telnumber::setline (string& newline)
	{
		line=newline;
	}

	string telnumber::getnpa()
	{
		return (npa);
	}

	string telnumber::getnxx()
	{
		return (nxx);
	}

	string telnumber::getline()
	{
		return (line);
	}

	telnumber::~telnumber()
	{
	}

class worknumber : public telnumber
{
public:
	worknumber();
	worknumber(string i_npa, string i_nxx, string i_line, string i_name);
	~worknumber();
	void setname(string& newname);
	string getnewname();
	virtual void printtostream(ostream& out);

protected:
	string name;

};

worknumber::worknumber():
	telnumber("","",""),
	name ("")
{
}

worknumber::worknumber(string i_npa, string i_nxx, string i_line, string i_name):
	telnumber(i_npa, i_nxx, i_line)
{
}

void worknumber::setname(string& newname)
{
	name=newname;
}

string worknumber::getnewname()
{
	return (name);
}

void printtostream(ostream& out)
{
	//crappy implementation removed
}

worknumber::~worknumber()
{
}

class billnumber : public worknumber
{
public:
	billnumber();
	billnumber(string i_npa, string i_nxx, string i_line, string i_name,int numlines=0);
	~billnumber();
	void setnumlines();
	int getnumlines();
	virtual void printtostream(ostream& out);

protected:
	int numlines;
};

billnumber::billnumber():
	worknumber("","","","")
	{
}

billnumber::billnumber(string i_npa, string i_nxx, string i_line, string i_name, int numlines):
	worknumber(i_npa, i_nxx, i_line, i_name)
{
}
	
void billnumber::setnumlines()
{
	numlines=0;
}

int billnumber::getnumlines()
{
	return (numlines);
}
	
billnumber::~billnumber()
{
}


//and then main

ostream& operator << (ostream &out, telnumber &tn)
{
	tn.printtostream(out);
	return out;
}

int main()
{
	telnumber yournumber;
	telnumber paul("719","590","6768");
	telnumber bob("719","590", "6729");
	worknumber csstaff1 ("719","590","6732","Book Store");
	worknumber csstaff2 ("212","371","6940","Borland C++ Guru");
	worknumber csstaff3 ("405","612","3433","Visual C++ Expert");
	billnumber csdept ("719","590","6850","Dean of CS");
	billnumber library ("719","598","6708","Librarian");
	billnumber reception ("719","598","0200","Receptionist",35);
	cout << "Testing the overladen << operator with the virtual" << "printtostream()\n\n";
	cout << "The telephone numbers are: \n" << endl;
	cout << yournumber << endl;
	cout << paul << endl;
	cout << bob << endl;
	cout << "The working telephone numbers are: \n" << endl;
	cout << csstaff1 << endl;
	cout << csstaff2 << endl;
	cout << csstaff3 << endl;
	cout << "The billing telephone numbers are: \n" << endl;
	cout << csdept << endl;
	cout << library << endl;
	cout << reception << endl;
	cout << "Here endeth the hierarchy of the telephone!" << endl;

return 0;
}

[Ancient Dragon]

line 105 needs the class soping in the name. You can not have just one function for all three classes -- you have to code one method for each class. Three classes, each class declared printtostream() so you must code each of the three methods, one for each class.

[henpecked1]

So even though I've declared the function to be pure virtual in telnumber, I still have to define it in telnumber cpp? I thought you didn't write an implementation for pure virtuals in the base class?

I understand about the scope, I just forgot to put it in...I did the same for billnumber

I have to work on a good implementation for the printtostream function also...so far I don't seem to be able to get it to work

[Ancient Dragon]

line 163 prevents you from making it a pure virtual function. You can't create an object of a class that has a pure virtual function, as you have already found out. So my previous idea to make it pure virtual won't work.

[henpecked1]

Yes, I found out...lol...I took the =0 out to make it just a plain ol virtual again, fixed the scope resolution in all the class cpp files, and just left the implementation blank for the moment. That at least gives me a screen and some output.

I can't for the life of me figure out the implementation of those virtuals though, nothing I put in outputs anything from main except 172, 173, 177, 181, and 185. I need to figure out how to make it see the other lines as "inputs" to those functions and I don't know how to do that

[mitrmkar]

I can't for the life of me figure out the implementation of those virtuals though, nothing I put in outputs anything from main except 172, 173, 177, 181, and 185. I need to figure out how to make it see the other lines as "inputs" to those functions and I don't know how to do that

Maybe the following helps ...

// telnumber
void telnumber::printtostream(ostream& out)
{
    out << "telnumber\n";
}

// worknumber
void worknumber::printtostream(ostream& out)
{
    telnumber::printtostream(out);
    out << "worknumber\n";
}

// billnumber
void billnumber::printtostream(ostream& out)
{
    worknumber::printtostream(out);
    out << "billnumber\n";
}

[henpecked1]

This is what that got me, but it's more than I had

from the console:

Testing the overladen << operator with the virtualprinttostream()

The telephone numbers are:

telnumber

telnumber

The working telephone numbers are:

telnumber
worknumber

telnumber
worknumber

telnumber
worknumber

The billing telephone numbers are:

telnumber
worknumber
billnumber

telnumber
worknumber
billnumber

telnumber
worknumber
billnumber

Here endeth the hierarchy of the telephone!
Press any key to continue . . .

[mitrmkar]

Now you can tailor those functions so that the output is what you want it to be and in desired order. I.e. on a per-class basis decide what you want to output.

[henpecked1]

everything from about line 163 us what I want to output, but I can't seem to get it to do that.

everything I try is wrong in some way and won't even compile on the individual cpp files...and when hey do compile, I get the same blank lines

[mitrmkar]

everything from about line 163 us what I want to output, but I can't seem to get it to do that.

everything I try is wrong in some way and won't even compile on the individual cpp files...and when hey do compile, I get the same blank lines

You need to devise something like ...

// telnumber
void telnumber::printtostream(ostream& out)
{
    // output npa, nxx and line
    out 
        << "npa: [" << npa << "]\n"
        << "nxx: [" << nxx << "]\n"
        << "line: [" << line << "]\n";
}
// worknumber
void worknumber::printtostream(ostream& out)
{
    // output the base class first ...
    telnumber::printtostream(out);

    // now worknumber data ...
    out << "name: [" << name << "]\n";
}

[henpecked1]

what do the semi colon and the brackets do? nm wasn't paying close enough attention....it still doesnt output the numbers...see below ... am I missing a function or something?

telnumber bob("719","590", "6729") is one of the lines in my main, yrt it doesnt take any of that as input

[mitrmkar]

what do the semi colon and the brackets do?

Those are just printable characters in the output simply for display purposes, i.e. the data of a single telnumber object would display on screen as:

npa: [ value_of_npa_here ]
nxx: [ value_of_nxx_here ]
line: [ value_of_line_here ]

They have no functional impact whatsoever.

[henpecked1]

okay, thats what I thought...so now I know I'm doing something wrong...I'm missing something somewhere, because I can't seem to pull the values from main and print them....now originally, I thought that was because I was screwing up the function that was supposed to print them to the screen...but maybe it's in the setters in my class, am I doing those wrong? (they are on the previous page)

[mitrmkar]

okay, thats what I thought...so now I know I'm doing something wrong...I'm missing something somewhere, because I can't seem to pull the values from main and print them....now originally, I thought that was because I was screwing up the function that was supposed to print them to the screen...but maybe it's in the setters in my class, am I doing those wrong? (they are on the previous page)

You need to assign the values in the ctor (they do not get assigned automatically)

telnumber::telnumber (string i_npa,string i_nxx,string i_line)
: 
  npa (i_npa),
  nxx (i_nxx),
  line (i_line)
{ }

[henpecked1]

awwww....I'm an idiot...I didn't even catch that. I knew I was missing an assignment or some other small detail