如何解决从main函数调用变量到其他类并无法使用它？
当所有类都放在一个包含所有类的主cpp文件中时，我能够运行该程序。但是，当我将cpp文件拆分为各自的头文件和cpp文件时，会出现一些错误。
下面是我正在使用的所有文件（它们都在一个文件夹中）：
1) Assignment.cpp (where the main function is at)
2) ShapeTwoD.cpp (Where the parent class is at)
3) ShapeTwoD.h
3) Square.cpp (Child Class)
4) Square.h
5) Rectangle.cpp (Child class)
6) Rectangle.h
问题1：
我有两个变量：
ShapeTwoD * Shape2D [100];
int size = 0;
以上变量位于主函数中。我试过在其他类中调用上述变量，但是有一个错误指出该变量未在作用域中声明。我也尝试添加extern，但是似乎也出现了一些错误。我已经将变量移到了父类Shape2D.cpp，但是，主cpp无法检测到变量名。我还公开放置在父cpp下。
如果有人可以帮我解决问题，我将不胜感激。最热烈的问候
Square.h：
Square.cpp：
class Square: public ShapeTwoD{
public:
Square(string name,bool containsWarpSpace,vector < pair<int,int> > vect):ShapeTwoD(name,containsWarpSpace,vect,radius){
this->vect = vect;
this->name = name;
this->containsWarpSpace = containsWarpSpace;
}
double computeArea();
bool isPointOnShape(int x,int y);
bool isPointInShape(int x,int y);
vector<pair<int,int> >allCoord();
void setInnerCoord(vector<pair<int,int> > innerCoord);
vector<pair<int,int> > getInnerCoord();
void setOuterCoord(vector<pair<int,int> > outerCoord);
vector<pair<int,int> > getOuterCoord();
string toString();
void calculatePerimeter();
~Square(){
}
};
double Square::computeArea(){
int width;
int area;
std::vector< pair<int,int> >::iterator result = std::max_element(this->vect.begin(),this->vect.end());
int positionMax = std::distance(this->vect.begin(),result);
pair<int,int> maxCoordinate = this->vect[positionMax];
for(int i = 0; i < this->vect.size(); i++){
if(this->vect[i].second == maxCoordinate.second && this->vect[i] != maxCoordinate){
width = maxCoordinate.first - this->vect[i].first;
area = width * width;
}
}
return area;
}
bool Square::isPointOnShape(int x,int y){
bool result = false;
std::vector< pair<int,int> >::iterator resultMax = std::max_element(this->vect.begin(),this->vect.end());
int positionMax = std::distance(this->vect.begin(),resultMax);
std::vector< pair<int,int> >::iterator resultMin = std::min_element(this->vect.begin(),this->vect.end());
int positionMin = std::distance(this->vect.begin(),resultMin);
pair<int,int> maxCoordinate = this->vect[positionMax];
pair<int,int> minCoordinate = this->vect[positionMin];
for(int i = 0; i < this->vect.size();i++){
if(maxCoordinate.first == x || maxCoordinate.second == y || minCoordinate.first == x || minCoordinate.second == y){
result = true;
}
else{
result = false;
}
}
return result;
}
ShapeTwoD.cpp（父类）：
class ShapeTwoD{
protected:
string name;
bool containsWarpSpace;
vector < pair<int,int> > vect;
int radius;
double area;
vector < pair<int,int> > innerCoord;
vector < pair<int,int> > outerCoord;
private:
public:
ShapeTwoD(){
}
ShapeTwoD(string name,int> > vect,int radius){
this->radius = radius;
this->vect = vect;
this->name = name;
this->containsWarpSpace = containsWarpSpace;
}
virtual double computeArea();
virtual bool isPointInShape(int x,int y);
virtual bool isPointOnShape(int x,int y);
virtual vector<pair<int,int> > allCoord();
virtual void setInnerCoord(vector<pair<int,int> > innerCord);
virtual vector<pair<int,int> > getInnerCoord();
virtual void setOuterCoord(vector<pair<int,int> > outerCoord);
virtual vector<pair<int,int> > getOuterCoord();
virtual string toString();
virtual void calculatePerimeter();
virtual ~ShapeTwoD(){
}
string getName();
bool getContainsWarpSpace();
void setName(string name);
void setContainsWarpSpace(bool containsWarpSpace);
void setCoord(vector < pair<int,int> > v);
vector < pair<int,int> > getCoord();
void setArea(double area);
double getArea();
};
主要功能（）：
int main() {
ShapeTwoD * obj;
int x;
int y;
int radius;
string menu = "0";
while(menu != "5"){
cout <<"----------------------------------" << endl;
cout << "1) Input sensor data" <<endl;
cout << "5) Quit\n" <<endl;
cout << "Please enter your choice:";
cin >> menu;
if(menu == "1"){
cout << "[ Input sensor data ]" << endl;
cout << "Please enter name of shape :";
cin >> shape;
transform(shape.begin(),shape.end(),shape.begin(),::tolower);
cout << "Please enter special type :";
cin >> specialtype;
transform(specialtype.begin(),specialtype.end(),specialtype.begin(),::tolower);
if(shape == "rectangle"){
vector < pair<int,int> > temp;
for(int i = 0; i < 4; i++){
cout << "Please enter x-ordinate of pt " << i+1 <<" :";
cin >> x;
cout << "Please enter y-ordinate of pt " << i+1 << " :";
cin >> y;
std::pair <int,int> p;
p = std::make_pair (x,y);
temp.push_back(p);
}
obj = new Rectangle(shape,"",temp);
if(specialtype == "ws"){
obj->setContainsWarpSpace(true);
}
else if (specialtype == "ns"){
obj->setContainsWarpSpace(false);
}
Shape2D[size] = obj;
size ++;
temp.clear();
cout << "\nRecords successfully stored. Going back to main menu ...\n" << endl;
}
else if(shape == "square" ){
vector < pair<int,int> > temp;
for(int i = 0; i < 4; i++){
cout << "Please enter x-ordinate of pt " << i+1 <<" :";
cin >> x;
cout << "Please enter y-ordinate of pt " << i+1 << " :";
cin >> y;
std::pair <int,y);
temp.push_back(p);
}
obj = new Square(shape,temp);
if(specialtype == "ws"){
obj->setContainsWarpSpace(true);
}
else if (specialtype == "ns"){
obj->setContainsWarpSpace(false);
}
temp.clear();
Shape2D[size] = obj;
size ++;
cout << "\nRecords successfully stored. Going back to main menu ...\n" << endl;
}
cout << "\nRecords successfully stored. Going back to main menu ...\n" << endl;
}
解决方法
对于问题一，最合理的位置是ShapeTwoD中的静态成员。将以下内容放在shapetwod.h中：
class ShapeTwoD {
public:
static vector<shared_ptr<ShapeTwoD>> allShapes;
};
并在shapetwod.cpp中输入一个定义：
vector<shared_ptr<ShapeTwoD>> ShapeTwoD::allShapes;
然后您可以使用ShapeTwoD::allShapes从其他位置访问此向量。
注意：从C ++ 17开始，您可以放弃多余的定义，并声明inline static。
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