getting linking Error while creating a flyweight_pattern [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 5 years ago.
#include <iostream>
#include <map>
#include <string>
#include <cstdlib>
using namespace std;
class Shape
{
public :
virtual void draw()=0;
virtual ~Shape(){}
};
class Circle : public Shape
{
string color;
int x;
int y;
int radius;
public:
Circle(string color){
color = color;
}
void setX(int x) {
x = x;
}
void setY(int y) {
y = y;
}
void setRadius(int radius) {
radius = radius;
}
void draw() {
cout << "color :" << color << x << y ;
}
};
class ShapeFactory {
public:
static map<string, Shape*> circlemap;
static Shape* getcircle(string color)
{
Shape *mcircle;
mcircle = circlemap.find(color)->second;
if(mcircle == nullptr) {
mcircle = new Circle(color);
circlemap[color] = mcircle;
// circlemap.insert(std::make_pair(color,mcircle));
}
return mcircle;
}
};
class Flyweightpattern
{
public:
static string getRandomColor(string colors[]) {
int m_rand = rand() % 5;
return colors[m_rand];
}
static int getRandomX() {
return (int)(rand() % 100);
}
static int getRandomY() {
return (int)(rand() % 100);
}
};
int main()
{
string colors[] = { "Red", "Green", "Blue", "White", "Black" };
for(int i=0; i < 20; ++i) {
Circle *circle = dynamic_cast<Circle *>(ShapeFactory::getcircle(Flyweightpattern::getRandomColor(colors)));
circle->setX(Flyweightpattern::getRandomX());
circle->setY(Flyweightpattern::getRandomY());
circle->setRadius(100);
circle->draw();
}
getchar();
return 0;
}
I am getting the linking error during run is below :
flyweight_pattern.obj : error LNK2001: unresolved external symbol
"public: static class std::map,class std::allocator >,class Circle
*,struct std::less,class std::allocator > >,class
std::allocator,class std::allocator > const ,class
Circle *> > > ShapeFactory::circlemap"
(?circlemap#ShapeFactory##2V?$map#V?$basic_string#DU?$char_traits#D#std##V?$allocator#D#2##std##PAVCircle##U?$less#V?$basic_string#DU?$char_traits#D#std##V?$allocator#D#2##std###2#V?$allocator#U?$pair#$$CBV?$basic_string#DU?$char_traits#D#std##V?$allocator#D#2##std##PAVCircle###std###2##std##A)
I have a map in the ShapeFactory class and tried to creating filling the map in the class itself but still not able to resolve the problem.

Answer 1

You didn't defined circlemap, it's a static member, so you should define it (and initialize) in global scope:
map<string, Shape*> ShapeFactory::circlemap = {};
Integral nonvolatile static members can be initialized in class.
Oh, and it is not recommended to do using namespace std; in global scope, that leads to side effects.
You can write something like
using std::map;
to target selected id (map in this case), and you can write using in namespace that contains usage.