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Array of class with inheritance

leeto (37)
Hi,all and thanks in advance. Shape base class, line and Point derived classes.
What should I declare in .h files and implement in .cpp files that this is array will be work.
My major concern refer to operator [] and assign (=) operator. As far as I understand I should overload ([]) and (=) three times for classes shape , line and point or not... or is it possible made through virtual function? How will be code looks like ? 


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 // part of main.cpp 
 Shape* shapes[3]; // Array of pointers to Shape

shapes[0] = new Shape();
shapes[1] = new Line ("line from array ", Point(1,22),Point(33,22));
shapes[2] = new Point(11,44);

cout << "using ToString function"  << endl;
for(int i=0; i < 3; i++)
cout << s[i]->ToString();

for(i=0; i < 3; i++)
delete s[i];
leeto (37)
May be I should say more about my problem... Please ask me )
vlad from moscow (6539)
You shall have virtual destructor and virtual operator function []. I do not see where you use the assignment operator.
ne555 (10692)
virtual operator function []
¿what for?
leeto (37)

" I do not see where you use the assignment operator." I thought I that I should make code for all classes Point, Line and ect. like code below or it is wrong

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Point& Shape::operator = ( Point& source)
{
    cout << " In the Array Assignment operator" << endl;
 
    if (this == &source)
        {
        cout << "Same Array " << endl;
        return *this;
        }
 
    delete [] m_data;
    cout <<"Deleted m_data array" << endl;
 
    m_size = source.m_size;  // shallow copy - this is not dynamic alloc
 
    if (source.m_data)  // if not zeros then there is a ref. - Deep copy needed
    {
        cout <<"im here"<<endl;
 
        m_data = new Point[source.m_size];  // create a new pointee.
 
        for (int i = 0; i < source.m_size; i++)
            m_data[i]    =    source.m_data[i]; //copy the points from/to array
    }
    else
        m_data = 0;  //NULL
 
    return *this;
}



how should see implementation of [] operator ?My code below I think unsuitable in this case. could you help me ? 

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Point& Shape::operator [] (int index)
{// My concern refer to Point&. I think it's not correct use this way... 
    cout << "Array [] operator" << endl;
 
    if (index > this->m_size)
	{
        cout << "i am hreeeee" << endl;
        return this->m_data[0];
	}
    return m_data[index];
}
leeto (37)
my virtual detractor will be only in shape.h ?
Last edited on
coder777 (8444)
When it comes to inheritance and pointers then operators like that are pretty useless. Use (virtual) functions instead.

if you want to delete a pointer to the base class then you need a virtual destructor for this base class. Because then the destructors of the sub classes are called otherwise not.
vlad from moscow (6539)
@ne555
virtual operator function []

¿what for?


For this code

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for(int i=0; i < 3; i++)
cout << s[i]->ToString();


In my opinion there is a typo. Shall be shapes[i] instead of s[i].
leeto (37)
I'm still out of trek could you post code or part of code ?
ne555 (10692)
Shall be shapes[i] instead of s[i].
Sure, but Shape* shapes[3];
As you see the [] is applied to the array, that would work well (returning the pointer to the 'K' shape)

If you overload the operator then you could be able to do shapes[i][0] ¿what would that mean?

May be I should say more about my problem... Please ask me
¿what is the problem?
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