Thread: Question

ok im trying to read in data from a file with this info

Ray L. Jones 3942 6 4 1974 3 2 2001

and i have a class like this

Code:

class Instructor {

public:
	Instructor();   // constructor
	~Instructor();	

private:
	string firstName;
	string lastName;
	string middleInitial;
	string employeeID;
	

}; // end class Instuctor

and my code in main looks like this. The line that says
inFile >> *(I[i_index]);
is not executing , it gives me an error and i think i would need to use operator overloading on a function for that line to be valid but im not sure.

Code:

Instructor *I[MAX_INSTRUCTORS] = {NULL_POINTER};

	for(int i_index = LOOP_BASE; i_index < MAX_INSTRUCTORS; i_index++)
	{
		I[i_index] = new Instructor();
		inFile >> *(I[i_index]); 
		//What must I do to my class Instructor to make the line of code above work?
		//cout << "The new instructor is " << *(I[i_index]) << ".\n";
   }

Try
inFile.read(reinterpret_cast<char *>(I[i_index]) sizeof(Instructor));

Although I think you're going to need to use a binary file with NULL seperating your strings.

I can't do that i really need to make that particular line of code work, does anyone have any ideas.

I used this for my string class. You can easily change it to make it work for your Instructor class.

Code:

//In your .h file
friend	ostream&	operator<<(ostream&,const String&);
friend	istream&	operator>>(istream&,String&);

//In your .cpp file
ostream& operator<<(ostream& o, const String& newStr)
{
	return o << newStr.lpzstr;
}

istream& operator>>(istream& i,String& obj)
{
	char buffer[1024];
	i.getline(buffer,1023,'\n');
	delete [] obj.lpzstr;
	obj.lpzstr = new char[strlen(buffer)+1];
	strcpy(obj.lpzstr, buffer);
	return i;
}

I see your code, but i don't see how that code would make this a vaild line of code

Code:

inFile >> *(I[i_index]);

How will that read from the file?

Hmm.... You were supposed to figure it out.

What, exactly, must happen when you do the following :

Code:

inFile >> *(I[i_index]);

its supposed to read in data from a file that looks like this

Ray L. Jones 3942 6 4 1974 3 2 2001
Alice K. Brown 8300 4 8 1969 2 1 1999

and store into a pointer of class Instructor which i have defined above and the line below the one that looks like this

Code:

inFile >> *(I[i_index]);

then the line that prints the code looks like this

Code:

cout << "The new instructor is " << *(I[i_index]) << ".\n";

which will print out something like this:
The new instructor is Ray L. Jones 3942

because i can't do that, i have to make it fit what is already in main.

ok i have overloaded the >> operator and in main i have a line of code like this Instructor *S[3] which is an array of 3 pointers to class Instructor and then also in main is the line:
inFile >> *(I[i_index]);

now the function that matches this is in my class Instructor which looks like this:

Code:

	friend istream &operator>>(ifstream &, Instructor *);

	

	

private:
	string firstName;
	string lastName;
	string middleInitial;
	string employeeID;

but in my definition of the function it says firstName, lastName and so on are undeclared

Code:

stream &operator>>(ifstream &I, Instructor *S)
{
	I>>firstName>>middleInitial>>lastName>>employeeID;
}

I'm doubting that you wrote this code yourself, or you're extremely sleepy. Think about it...

Code:

const ifstream &operator>>(ifstream &I, Instructor *S)
{
    I >> S->firstName >> S->middleInitial >> S->lastName 
      >> S->employeeId;

    return I;
}

This code is in main

Code:

for(int i_index = LOOP_BASE; i_index < MAX_INSTRUCTORS; i_index++)
	{
		I[i_index] = new Instructor();
		inFile >> *(I[i_index]);

This is in class Instructor

Code:

class Instructor {

public:
	Instructor();   // constructor
	~Instructor();
	friend istream &operator>>(ifstream &I, Instructor *S);

and this is in the member functions file

Code:

ifstream &operator>>(ifstream &I, Instructor *S)
{
    I >> S->firstName >> S->middleInitial >> S->lastName 
      >> S->employeeID;

}

it gives me this error
Compiling...
Driver.cpp
C:\Documents and Settings\Massa\Driver.cpp(91) : error C2679: binary '>>' : no operator defined which takes a right-hand operand of type 'class Instructor' (or there is no acceptable conversion)
Error executing cl.exe.

Driver.exe - 1 error(s), 0 warning(s)

Again wake up...and think a little...

Code:

inFile >> *(I[i_index]);

in the above line you're passing an Instructor object to the operator NOT its address. You either need to change it, or change the operator definition...

Code:

const ifstream &operator>>(ifstream &I, Instructor &S)
{
    I >> S.firstName >> S.middleInitial >> S.lastName 
      >> S.employeeID;
}

dont forget to return the ifstream reference in the defintion...