Call Function From An Vector of Pointers of Abstract Class - c++

Question

I have an abstract class with 2 pure virtual functions:
class CCobjectBase
{
public:
CCobjectBase();
virtual void setCordFigure(double *, int) = 0;
virtual double* getCord() = 0;
};
And a class that is derived from the abstract one:
class CTriangle : public CCobjectBase
{
public:
CTriangle();
~CTriangle();
void setCordFigure(double *, int);
double* getCord();
private:
double *m_cord;
int m_size;
}
void CTriangle :: setCordFigure(double *cord, int size)
{
m_cord = cord;
m_size = size;
}
double * CTriangle :: getCord()
{
return m_cord;
}
I used a vector of pointers to the abstract class:
std::vector<CCobjectBase *> m_objectBaseList;
And i create and store some values in this vector as follow:
m_objectBaseList.push_back(new CTriangle());
m_objectBaseList.at(m_objectBaseList.size() - 1) -> setCordFigure(coordonate, size);
The problem occurs when i try to display the values from the vector:
for(size_t i=0; i< m_objectBaseList.size(); i++)
{
double * cord = m_objectBaseList.at(i) -> getCord();
out<<cord[0]<<" "<<cord[1]<<" "<<cord[2]<<" "<<cord[3]<<" "<<cord[4]<<" "<<cord[5]<<endl;
}
It seems that all the objects have the same values stored. I tried multiple solution but i can not simply figure it out. If i give inputs as follow:
Object1: 1 2 3 4 5 6
Object2: 3 2 3 3 5 5
...
Objectn: 1 1 2 2 1 1
All objects have the value of Objectn:
Object1: 1 1 2 2 1 1
Object2: 1 1 2 2 1 1
...
Objectn: 1 1 2 2 1 1
The problem is not from the parameter coordonate because i tested in the setCordFigure(double *cord, int size){} function and it shows fine.
Any possible sugestions?
EDIT:
The portion of the code where I set the values is actually like this:
void MainWindow :: creazaObiecte(int numarOrdine, double *coordonate, int size)
{
QTextStream out(stdout);
switch(numarOrdine)
{
case 1:
m_objectBaseList.push_back(new CTriangle());
m_objectBaseList.at(m_objectBaseList.size() - 1) -> setCordFigure(coordonate, size);
break;
...
}
}
I use this function from each line of a file what I read. The portion of the code where I call this function is something like:
while(--condition--)
{
double coordonate[30]; //coordonate is used to store values as an array Ex: 20 30 12 2 32 12 etc
//fill coordonate with values from the line of the file
creazaObiecte(ordinClasa, coordonate, size); //ordinClasa is a variable that stores the index of the object (1 stands for triangle)
}

Answer 1

EDIT: My original answer was in a context where I didn't realise m_coord is meant to be an array, so was inappropriate.
Your operation setCordFigure just sets your m_coord member pointer to the passed argument. It does not not copy the underlying array. So in the end all your objects end up pointing to the same array.
You need to actually copy the array in your setCordFigure function. You could do this with naked arrays, but its better to use a vector. So this is possible code:
class CCobjectBase
{
public:
CCobjectBase();
virtual void setCordFigure(const std::vector<double>&) = 0;
virtual std::vector<double>& getCord() = 0;
};
class CTriangle : public CCobjectBase
{
public:
CTriangle();
~CTriangle();
void setCordFigure(const std::vector<double>&);
std::vector<double>& getCord();
private:
std::vector<double> m_cord;
int m_size;
}
void CTriangle :: setCordFigure(const std::vector<double>& cord)
{
m_cord = cord;
}
std::vector<double>& CTriangle :: getCord()
{
return m_cord;
}
Then your creation function becomes:
void MainWindow :: creazaObiecte(int numarOrdine, const std::vector<double>& coordonate)
{
QTextStream out(stdout);
switch(numarOrdine)
{
case 1:
m_objectBaseList.push_back(new CTriangle());
m_objectBaseList.at(m_objectBaseList.size() - 1) -> setCordFigure(coordonate);
break;
...
}
}
And your population function becomes:
while(--condition--)
{
std::vector<double> coordonate(30); //coordonate is used to store values as an array Ex: 20 30 12 2 32 12 etc
//fill coordonate with values from the line of the file
creazaObiecte(ordinClasa, coordonate); //ordinClasa is a variable that stores the index of the object (1 stands for triangle)
}

Answer 2

double *m_cord;
You are storing a pointer to the coordinate in your class.
void CTriangle :: setCordFigure(double *cord, int size)
Then, probably, you are reading the "input" into some variables, which are then referenced in your CTriangle objects. So as the values of the variables are changed, all of the objects are really pointing to the same stuff.