获取链接 创建flyweight_pattern时出错

#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;
}

我在运行期间收到以下链接错误：

flyweight_pattern.obj：错误LNK2001：未解析的外部符号 "public： 静态类 std：：map，class std：：分配器>，类圈 *，结构标准：：更少，类标准：：分配器>>，类 标准：：分配器，类 标准：：分配器> 常量，类 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(

我在 ShapeFactory 类中有一个地图，并尝试在类本身中创建填充地图，但仍然无法解决问题。