Cannot get the value from a class in C++? - c++

Question

I just came from Java and Python world to C++ world, and faced a problem while trying to get the value from a public const function of a class.
I have a class as follows:
class CMDPoint
{
public:
CMDPoint();
CMDPoint(int nDimensions);
virtual ~CMDPoint();
private:
int m_nDimensions; // the number of dimensions of a point
float* m_coordinate; // the coordinate of a point
public:
const int GetNDimensions() const { return m_nDimensions; }
const float GetCoordinate(int nth) const { return m_coordinate[nth]; }
void SetCoordinate(int nth, float value) { m_coordinate[nth] = value; }
};
Ultimately, I wish to write all the clusterPoints in clusterPointArray into the file. However, now I am just testing it with the first clusterPoint (thus, GetCoordinate(0)).
ofstream outFile;
outFile.open("C:\\data\\test.txt", std::ofstream::out | std::ofstream::app);
for (std::vector<CMDPoint> ::iterator it = clusterEntry->clusterPointArray.begin(); it != clusterEntry->clusterPointArray.end(); ++it)
{
outFile << ("%f", (*it).GetCoordinate(0)); // fails
outFile << " ";
}
outFile << "\n";
outFile.close();
The problem is I only see the " " in the file. No coordinate has been written in. Did I do anything wrong while fetching the value from const float GetCoordinate(int nth)?

Answer 1

try to change this
outFile << ("%f", (*it).GetCoordinate(0)); // fails
to this:
outFile << (*it).GetCoordinate(0); // OK
Because the ("%f", (*it).GetCoordinate(0)) represents nothing , only a enumerations of expressions separated by , . It will not be evaluated into a pair of objects as in java is i think.
Edit:("%f", (*it).GetCoordinate(0)) actually evaluates to the last element that is (*it).GetCoordinate(0) ( PlasmaHH comment ) so it should still print something. However if nothing is printed then the collection clusterEntry->clusterPointArray could be empty and the code inside the for loop might not be executed ever.
Hope this helps,
Razvan.

Answer 2

outFile << it->GetCoordinate(0);