Class array with variable number of elements

[DL30RXSz]

I'm creating a class which represents a polygon, and I want it to be able to set the number of sides when constructed so I wrote this code:

class Polygon
{
public:
	Polygon(int initNumOfSides){ numOfSides = initNumOfSides; }
	~Polygon(){ ;}

	void SetSide(int side, double value);
	double GetSide(int side);
private:
	int numOfSides;
	double sides[numOfSides]; /* line 37 */
	double height;
};

void Polygon::SetSide(int side, double value)
{
	sides[side-1] = value;
}

double Polygon::GetSide(int side)
{
	return sides[side-1];
}

This gives me two errors.
error C2327: 'Polygon::numOfSides' : is not a type name, static, or enumerator
error C2065: 'numOfSides' : undeclared identifier

How should I do this?

[firedraco]

That's not how you make a dynamic array. You would need to use new in your constructor and delete in the destructor. Look here for more info: http://www.cplusplus.com/doc/tutorial/dynamic/

You could also use a vector and set it's size when you construct your own object so you don't have to worry about deleting it.

[DL30RXSz]

Thank you, that works much better. Here is my new code:

class Polygon
{
public:
	Polygon(int initNumOfSides){ sides = new (nothrow) double[initNumOfSides]; }
	~Polygon(){ ;}

	void SetSide(int side, double value);
	double GetSide(int side);
private:
	double* sides;
	double height;
};

Will the array be deleted automatically when the destructor is run? If not, can I tell it to do so int the destructor's definition?

[Disch]

Will the array be deleted automatically when the destructor is run?

No

If not, can I tell it to do so int the destructor's definition?

Yes:

~Polygon(){ delete[] sides; }

Also note that you should probably make a copy constructor and assignment operator too, otherwise you'll have problems if you copy Polygons.