C++: Issues with handling Errors in Abstract Class - c++

Question

Iam currently working on an assignment wherein;
I have to create my own array and array exception class.
SetElement(int arg) and GetElement(int arg) part of Array class, need to account for out of bound exceptions by throwing OutOfBoundsExcpetoinObject(Derrived) part of the Array Exception class (Base).,
I have to catch the Array Exception (base class).
I am getting an error that the abstract class cannot be caught.
These are the parameters. I have followed them, however i am still getting the abstract class cannot be caught error.
1.Give the ArrayException an abstract GetMessage() function that returns a std::string.
2.Give the OutOfBoundsException class a constructor with an int as argument that indicates the erroneous array index and store it in a data member.
3.Override the GetMessage() function and let the implementation return a message string saying the given index is out of bounds.
4.In the Array class, throw now a OutOfBoundsException object instead of an integer.
5.Change the main program so that it catches the ArrayException base class and uses the GetMessage() function to display an error message.
Main Function:
// creating an array
Array abc =Array(5);
Point* q = new Point(1,2);
//testing out of bounds cases in both get and set
abc.setElement(10,*q);
cout << abc.getElement(10);
ArrayException Class:
class ArrayException
{
private:
public:
ArrayException();
virtual string GetMessage() const=0;
};
class OutofBoundsException : public ArrayException
{
private:
int m_index;
public:
OutofBoundsException();
OutofBoundsException(int index);
virtual string GetMessage() const;
};
Array Class:
Array::Array():m_size(3),m_data(new CAD::Point[m_size]) {}
Array::Array(int size): m_size(size), m_data(new CAD::Point[m_size]) {}
Array::~Array()
{
delete[] m_data;
cout << "Destructor called" << endl;
}
Array::Array(const Array &obj) {
m_size = obj.m_size;
m_data = new CAD::Point[m_size];
for (int i = 0; i < m_size; i++)
{
m_data[i] = obj.operator[](i);
}
}
int Array::Size()
{
return m_size;
}
udbhavAg::CAD::Point &Array::getElement(int index)
{
try
{
if (index >= m_size || index < 0)
{
OutofBoundsException error = OutofBoundsException(index);
throw (error);
}
else
{
return m_data[index];
}
}
catch (ArrayException abc)
{
cout << abc.GetMessage();
}
}
void Array::setElement(int index, udbhavAg::CAD::Point p)
{
try
{
if (index >= m_size || index < 0)
{
OutofBoundsException error = OutofBoundsException(index);
throw (error);
}
else
{
m_data[index] = p;
}
}
catch (ArrayException error)
{
cout << error.GetMessage();
}
}
Array Array::operator=(const Array &source)
{
if (this == &source)
{
return *this;
}
m_data = source.m_data;
m_size = source.m_size;
return *this;
}
CAD::Point &Array::operator[](int index) {
return m_data[index];
}
const CAD::Point &Array::operator[](int index) const {
return m_data[index];
}

Answer 1

You should catch by reference to base, which can bind to a derived object:
catch (ArrayException const& abc)
Then just throw OutofBoundsException(index) directly,

Answer 2

I solved the error using referecnig and dereferencing. Since an instance of abstract class cannot be created it cannot be caught. However, an abstract class pointer can be created, hence i figured it can be caught.
I changed the code in my setElement & GetElement to the following and it works now:
udbhavAg::CAD::Point &Array::getElement(int index)
{
try
{
if (index >= m_size || index < 0)
{
OutofBoundsException error = OutofBoundsException(index);
ArrayException& abc = error;
throw (&abc);
}
else
{
return m_data[index];
}
}
catch (ArrayException *error)
{
cout << error->GetMessage();
}
}
void Array::setElement(int index, udbhavAg::CAD::Point p)
{
try
{
if (index >= m_size || index < 0)
{
OutofBoundsException error = OutofBoundsException(index);
ArrayException& abc = error;
throw (&abc);
}
else
{
m_data[index] = p;
}
}
catch (ArrayException *error)
{
cout << error->GetMessage();
}
}