An error I don't understand [duplicate] - c++

Question

This question already has answers here:
What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 8 years ago.
I'm getting this error when I compile, but I'm not sure how to fix it. I see that it has something to do with trying to use ofstream outFile; to write to a file. I've diddled with it, but I'm not sure what the problem is.
1>Rectangle.obj : error LNK2001: unresolved external symbol "class std::basic_ofstream<char,struct std::char_traits<char> > outFile" (?outFile##3V?$basic_ofstream#DU?$char_traits#D#std###std##A)
1>E:\Hw11_overload_Hw8\Debug\Rectangle.exe : fatal error LNK1120: 1 unresolved externals
This is my header file.
#ifndef Rectangle_h
#define Rectangle_h
#include <iostream>
#include <fstream>
#include <sstream>
using namespace std;
class Rectangle
{
friend istream &operator>> (istream &input, Rectangle &grid);
friend ostream &operator<< (ostream &output, Rectangle grid);
private:
int i, j, h, x1, x2, y1, y2, perimeter, area, width, height;
char inner, outer;
string name;
public:
Rectangle();
void printGrid();
void setX1(int x11);
int getX1();
void setX2(int x21);
int getX2();
void setY1(int y11);
int getY1();
void setY2(int y21);
int getY2();
void setInner(char inner1);
char getInner();
void setOuter(char outer1);
char getOuter();
void findPerimeter();
void findArea();
void findWidth();
void findHeight();
void setName(string name1);
string getName();
int Menu();
};
#endif
And here is my source file.
#include "Rectangle.h"
extern ofstream outFile;
Rectangle::Rectangle()
{
x1 = 0;
x2 = 1;
y1 = 0;
y2 = 1;
}
void Rectangle::setX1(int x11)
{
x1 = x11;
}
int Rectangle::getX1()
{
return x1;
}
void Rectangle::setX2(int x21)
{
x2 = x21;
}
int Rectangle::getX2()
{
return x2;
}
void Rectangle::setY1(int y11)
{
y1 = y11;
}
int Rectangle::getY1()
{
return y1;
}
void Rectangle::setY2(int y21)
{
y2 = y21;
}
int Rectangle::getY2()
{
return y2;
}
void Rectangle::findPerimeter()
{
perimeter = ((x2 - x1) + (y2 - y1)) * 2;
cout << "The perimeter of the rectangle is: " << perimeter << endl;
}
void Rectangle::findArea()
{
area = (x2 - x1) * (y2 - y1);
cout << "The area of the rectangle is: " << area << endl;
}
void Rectangle::findWidth()
{
width = x2 - x1;
cout << "The width of the rectangle is: " << width << endl;
}
void Rectangle::findHeight()
{
height = y2 - y1;
cout << "The height of the rectangle is: " << height << endl;
}
void Rectangle::setInner(char inner1)
{
inner = inner1;
}
char Rectangle::getInner()
{
return inner;
}
void Rectangle::setOuter(char outer1)
{
outer = outer1;
}
char Rectangle::getOuter()
{
return outer;
}
void Rectangle::setName(string name1)
{
name = name1;
}
string Rectangle::getName()
{
return name;
}
void Rectangle::printGrid()
{
int numrows = 25;
int numcols = 25;
int current_row = numrows; // starting row number
int current_col = 1; // starting col number
char output = '.';
for(i = 0; i < numrows; i++) // prints 25 rows of 25 dots
{
cout << current_row << '\t'; // Print out current row number
outFile << current_row << '\t';
//This is out loop for each ROW
//Print out dots in each row OR stuff for the rectangle
for(j = 1; j <= numcols; j++) {
output = '.'; // Initialize output with our default value of "."
if ((current_col >= x1) && (current_col <= x2) && (current_row >= y1) && (current_row <= y2)) {
output = outer;
}
if ((current_col > x1) && (current_col < x2) && (current_row > y1) && (current_row < y2)) {
output = inner;
}
cout << output << " "; // output our "output" value and a space
outFile << output << " ";
current_col++; //Increment current column, because this is the end of this column loop iteration
} // Close column loop
cout << endl; //...and a new line
outFile << endl;
current_col = 1; // reset column count for next iteration
current_row--; // decrement current row number
} // Close Row loop
//output column labels across bottom line
cout << '\t';
outFile << '\t';
// put 1 -> 25 across the bottom
for (i = 1; i <= 25; i++)
{
if(i < 10)
{
cout << i << " ";
outFile << i << " ";
}
if(i > 9)
{
cout << i << " ";
outFile << i << " ";
}
}
// Spit out a couple of blank lines
cout << endl << endl;
outFile << endl << endl;
}
int Rectangle::Menu()
{
ifstream inFile;
int choice;
cout << "1. Enter information about a rectangle. " << endl;
cout << "2. Search for a rectangle. " << endl;
cout << "3. Print the perimeter and the area of the rectangle. " << endl;
cout << "4. Print the width and height of the rectangle. " << endl;
cout << "5. Draw a particular rectangle. " << endl;
cout << "6. Quit. " << endl;
cout << "Enter your choice. " << endl;
inFile >> choice;
cout << endl << endl;
return choice;
}
istream &operator>> (istream &input, Rectangle &grid)
{
ifstream inFile;
ofstream outFile;
Rectangle rect[10];
int x11, x21, y11, y21, choice, numRectangles = 0, i = 0;
char inner1, outer1;
string name1;
inFile.open ("rectangle.in");
outFile.open ("rectangle.out");
if (!inFile)
{
cout << "ERROR: inFile does not exist. " << endl;
system("pause");
}
if (!outFile)
{
cout << "ERROR: outFile does not exist. " << endl;
system("pause");
}
choice = rect[i].Menu();
while(choice >= 1 && choice <= 6)
{
if(choice == 1)
{ do
{
cout << "Enter x1, x2, y1, and y2 such that x1 < x2 and y1 < y2: " << endl;
inFile >> x11;
inFile >> x21;
inFile >> y11;
inFile >> y21;
cout << "Enter a character for the interior of the rectangle. \n";
inFile >> inner1;
cout << "Enter a character for the exterior of the rectangle. \n";
inFile >> outer1;
cout << "Enter a name for the rectangle. \n";
inFile >> name1;
rect[numRectangles].setX1(x11);
rect[numRectangles].setX2(x21);
rect[numRectangles].setY1(y11);
rect[numRectangles].setY2(y21);
rect[numRectangles].setInner(inner1);
rect[numRectangles].setOuter(outer1);
rect[numRectangles].setName(name1);
numRectangles++;
}
while(x11 >= x21 || y11 >= y21);
cout << endl << "Rectangle accepted. \n" << endl;
}
if (choice == 2)
{
cout << "To search for a rectangle, enter the name of the rectangle. " << endl;
cin >> name1;
for(i = 0; i < numRectangles; i++)
{
if(name1 == rect[i].getName())
{
rect[i].findPerimeter();
rect[i].findArea();
rect[i].findWidth();
rect[i].findHeight();
rect[i].printGrid();
system("pause");
}
}
if(name1 != rect[i].getName())
{
cout << "ERROR! Rectangle doesn't exist!" << endl << endl;
system("pause");
}
}
if(choice == 3)
{
for(i = 0; i < numRectangles; i++)
{
rect[i].findPerimeter();
cout << endl;
rect[i].findArea();
cout << endl;
}
}
if(choice == 4)
{
for(i = 0; i < numRectangles; i++)
{
rect[i].findWidth();
cout << endl;
rect[i].findHeight();
cout << endl;
}
}
if(choice == 5)
{
for(i = 0; i < numRectangles; i++)
{
rect[i].printGrid();
cout << endl;
}
}
if(choice == 6)
{
cout << "Bye bye!" << endl;
system("pause");
}
choice = rect[i].Menu();
return input;
} // End of while loop
inFile.close();
outFile.close();
}
ostream &operator<< (ostream &output, Rectangle grid)
{
return output;
}
And here is my main function
#include "Rectangle.h"
int main()
Rectangle rect[10];
int numRectangles;
for(int i = 0; i < numRectangles; i++)
{
cin >> rect[i];
cout << rect[i];
}
}

Answer 1

Problems:
You have declared that outFile will have external linkage. std::ofstream has no default constructor.
std::ofstream has a non-default constructor and takes two parameters.. The first is the location of the file and the second (which is default btw) is how you plan to open/write it.
Thus you can fix this error by replacing extern ofstream outFile; with:
ofstream outFile("output.txt"); within Rectangle.cpp
There is no need to declare it as extern within the .cpp file as far as I am aware.
Next, istream& operator>> (istream& input, Rectangle& grid) is returning NOTHING..
It should be returning input before the function finishes.
Finally, you are missing a curly bracket after main's () brackets.
You main.cpp should look like:
#include "Rectangle.h"
int main()
{
Rectangle rect[10];
int numRectangles;
for(int i = 0; i < numRectangles; i++)
{
cin >> rect[i];
cout << rect[i];
}
}
Would it really kill you to follow convention and format your code?
If done correctly, your code would look like:
Rectangle.h:
#ifndef Rectangle_h
#define Rectangle_h
#include <iostream>
#include <fstream>
#include <sstream>
using namespace std;
class Rectangle
{
private:
friend istream& operator>> (istream& input, Rectangle& grid);
friend ostream& operator<< (ostream& output, Rectangle grid);
int i, j, h, x1, x2, y1, y2, perimeter, area, width, height;
char inner, outer;
string name;
public:
Rectangle();
void printGrid();
void setX1(int x11);
int getX1();
void setX2(int x21);
int getX2();
void setY1(int y11);
int getY1();
void setY2(int y21);
int getY2();
void setInner(char inner1);
char getInner();
void setOuter(char outer1);
char getOuter();
void findPerimeter();
void findArea();
void findWidth();
void findHeight();
void setName(string name1);
string getName();
int Menu();
};
#endif
Rectangle.cpp:
#include "Rectangle.h"
ofstream outFile("output.txt");
Rectangle::Rectangle()
{
x1 = 0;
x2 = 1;
y1 = 0;
y2 = 1;
}
void Rectangle::setX1(int x11)
{
x1 = x11;
}
int Rectangle::getX1()
{
return x1;
}
void Rectangle::setX2(int x21)
{
x2 = x21;
}
int Rectangle::getX2()
{
return x2;
}
void Rectangle::setY1(int y11)
{
y1 = y11;
}
int Rectangle::getY1()
{
return y1;
}
void Rectangle::setY2(int y21)
{
y2 = y21;
}
int Rectangle::getY2()
{
return y2;
}
void Rectangle::findPerimeter()
{
perimeter = ((x2 - x1) + (y2 - y1)) * 2;
cout << "The perimeter of the rectangle is: " << perimeter << endl;
}
void Rectangle::findArea()
{
area = (x2 - x1) * (y2 - y1);
cout << "The area of the rectangle is: " << area << endl;
}
void Rectangle::findWidth()
{
width = x2 - x1;
cout << "The width of the rectangle is: " << width << endl;
}
void Rectangle::findHeight()
{
height = y2 - y1;
cout << "The height of the rectangle is: " << height << endl;
}
void Rectangle::setInner(char inner1)
{
inner = inner1;
}
char Rectangle::getInner()
{
return inner;
}
void Rectangle::setOuter(char outer1)
{
outer = outer1;
}
char Rectangle::getOuter()
{
return outer;
}
void Rectangle::setName(string name1)
{
name = name1;
}
string Rectangle::getName()
{
return name;
}
void Rectangle::printGrid()
{
int numrows = 25;
int numcols = 25;
int current_row = numrows; // starting row number
int current_col = 1; // starting col number
char output = '.';
for(i = 0; i < numrows; i++) // prints 25 rows of 25 dots
{
cout << current_row << '\t'; // Print out current row number
outFile << current_row << '\t';
//This is out loop for each ROW
//Print out dots in each row OR stuff for the rectangle
for(j = 1; j <= numcols; j++)
{
output = '.'; // Initialize output with our default value of "."
if ((current_col >= x1) && (current_col <= x2) && (current_row >= y1) && (current_row <= y2))
{
output = outer;
}
if ((current_col > x1) && (current_col < x2) && (current_row > y1) && (current_row < y2))
{
output = inner;
}
cout << output << " "; // output our "output" value and a space
outFile << output << " ";
current_col++; //Increment current column, because this is the end of this column loop iteration
} // Close column loop
cout << endl; //...and a new line
outFile << endl;
current_col = 1; // reset column count for next iteration
current_row--; // decrement current row number
} // Close Row loop
//output column labels across bottom line
cout << '\t';
outFile << '\t';
// put 1 -> 25 across the bottom
for (i = 1; i <= 25; i++)
{
if(i < 10)
{
cout << i << " ";
outFile << i << " ";
}
if(i > 9)
{
cout << i << " ";
outFile << i << " ";
}
}
// Spit out a couple of blank lines
cout << endl << endl;
outFile << endl << endl;
}
int Rectangle::Menu()
{
ifstream inFile;
int choice;
cout << "1. Enter information about a rectangle. " << endl;
cout << "2. Search for a rectangle. " << endl;
cout << "3. Print the perimeter and the area of the rectangle. " << endl;
cout << "4. Print the width and height of the rectangle. " << endl;
cout << "5. Draw a particular rectangle. " << endl;
cout << "6. Quit. " << endl;
cout << "Enter your choice. " << endl;
inFile >> choice;
cout << endl << endl;
return choice;
}
istream& operator>> (istream& input, Rectangle& grid)
{
ifstream inFile;
ofstream outFile;
Rectangle rect[10];
int x11, x21, y11, y21, choice, numRectangles = 0, i = 0;
char inner1, outer1;
string name1;
inFile.open ("rectangle.in");
outFile.open ("rectangle.out");
if (!inFile)
{
cout << "ERROR: inFile does not exist. " << endl;
system("pause");
}
if (!outFile)
{
cout << "ERROR: outFile does not exist. " << endl;
system("pause");
}
choice = rect[i].Menu();
while(choice >= 1 && choice <= 6)
{
if(choice == 1)
{
do
{
cout << "Enter x1, x2, y1, and y2 such that x1 < x2 and y1 < y2: " << endl;
inFile >> x11;
inFile >> x21;
inFile >> y11;
inFile >> y21;
cout << "Enter a character for the interior of the rectangle. \n";
inFile >> inner1;
cout << "Enter a character for the exterior of the rectangle. \n";
inFile >> outer1;
cout << "Enter a name for the rectangle. \n";
inFile >> name1;
rect[numRectangles].setX1(x11);
rect[numRectangles].setX2(x21);
rect[numRectangles].setY1(y11);
rect[numRectangles].setY2(y21);
rect[numRectangles].setInner(inner1);
rect[numRectangles].setOuter(outer1);
rect[numRectangles].setName(name1);
numRectangles++;
}
while(x11 >= x21 || y11 >= y21);
cout << endl << "Rectangle accepted. \n" << endl;
}
if (choice == 2)
{
cout << "To search for a rectangle, enter the name of the rectangle. " << endl;
cin >> name1;
for(i = 0; i < numRectangles; i++)
{
if(name1 == rect[i].getName())
{
rect[i].findPerimeter();
rect[i].findArea();
rect[i].findWidth();
rect[i].findHeight();
rect[i].printGrid();
system("pause");
}
}
if(name1 != rect[i].getName())
{
cout << "ERROR! Rectangle doesn't exist!" << endl << endl;
system("pause");
}
}
if(choice == 3)
{
for(i = 0; i < numRectangles; i++)
{
rect[i].findPerimeter();
cout << endl;
rect[i].findArea();
cout << endl;
}
}
if(choice == 4)
{
for(i = 0; i < numRectangles; i++)
{
rect[i].findWidth();
cout << endl;
rect[i].findHeight();
cout << endl;
}
}
if(choice == 5)
{
for(i = 0; i < numRectangles; i++)
{
rect[i].printGrid();
cout << endl;
}
}
if(choice == 6)
{
cout << "Bye bye!" << endl;
system("pause");
}
choice = rect[i].Menu();
return input;
} // End of while loop
inFile.close();
outFile.close();
return input;
}
ostream& operator<< (ostream& output, Rectangle grid)
{
return output;
}
main.cpp:
#include "Rectangle.h"
int main()
{
Rectangle rect[10];
int numRectangles;
for(int i = 0; i < numRectangles; i++)
{
cin >> rect[i];
cout << rect[i];
}
}
I did not check anything else other than getting it to compile. That means I am not sure if you have any bugs preventing it from running correctly. I also would advice you to avoid using using namespace std; in header files.