Inherited Class Problems

Question 1

Made some modification in your code. Please find fixed code below -

#include <iostream>
#include <iomanip>
using namespace std;
// Base

class IMatriz;

class IMatriz {
    int **m;
    int numRows;
    int numColumns;
public:
    IMatriz(){
        numRows = 0;
        numColumns = 0;
        m = NULL;
    }
    IMatriz(int r, int c) {
        numRows = r;
        numColumns = c;
        m = new int* [numRows];
        for(int i=0; i < numRows; i++)
            m[i] = new int [numColumns];
    }
    virtual void setSize(int r, int c) = 0;
    virtual void setValue(int row, int col, int val) = 0;
    virtual int getValue(int row, int col) = 0;
    virtual int getNumRows() = 0;
    virtual int getNumColumns() = 0;
    virtual void mult(IMatriz &a, IMatriz &b) = 0;
    virtual void print(void) = 0;
};
// Inherited
class Matriz : public IMatriz {
protected:
    int **m;
    int numRows;
    int numColumns;
public:
    Matriz()
    :  IMatriz()
    {
    }

    Matriz(int r, int c)
    :  IMatriz(r, c)
    {
        numRows = r;
        numColumns = c;
        m = new int* [numRows];

        for(int i=0; i < numRows; i++)
            m[i] = new int [numColumns];
    }

    void setSize(int r, int c);
    void setValue(int row, int col, int val);
    int getValue(int row, int col);
    int getNumRows();
    int getNumColumns();
    void mult(IMatriz &a, IMatriz &b);
    void print();
};
// Functions
void Matriz::setSize(int r, int c) {
    numRows = r;
    numColumns = c;
}
void Matriz::setValue(int row, int col, int val) {
    m[row][col] = val;
}
int Matriz::getValue(int row, int col) {
    return m[row][col];
}
int Matriz::getNumRows() {
    return numRows;
}
int Matriz::getNumColumns() {
    return numColumns;
}
void Matriz::mult(IMatriz &a, IMatriz &b) {
    //   m.setSize( a.getNumRows(), b.getNumColumns() );
    //   for (int rows = 0; rows < numRows; rows ++)
    //      for (int cols = 0; cols < numColumns; cols ++)
    //         m[rows][cols] = 0;
    //   for (int rows = 0; rows < a.getNumRows(); rows ++)
    //      for (int cols = 0; cols < b.getNumColumns(); cols ++)
    //         for (int auxl = 0; auxl < a.getNumColumns(); auxl ++)
    //            m[rows][cols] += (a[rows][auxl] * b[auxl][cols]);
    return;
}
void Matriz::print() {
    for (int rows  = 0; rows < numRows; rows ++)
    {
        for (int cols = 0; cols < numColumns; cols ++)
            cout << m[rows][cols] << " ";

        cout << endl;
    }
}
// Principal
int main(int argc, const char * argv[]) {
    Matriz m;
    Matriz a(3, 2);
    Matriz b(2, 3);
    a.setValue(0,0,7);
    a.setValue(0, 0, 7);
    a.setValue(1, 0, 1);
    a.setValue(2, 0, 8);
    a.setValue(0, 1, 2);
    a.setValue(1, 1, 5);
    a.setValue(2, 1, 6);
    b.setValue(0, 0, 2);
    b.setValue(1, 0, 3);
    b.setValue(0, 1, 5);
    b.setValue(1, 1, 4);
    b.setValue(0, 2, 8);
    b.setValue(1, 2, 9);
    a.print();
    b.print();
    //   m.mult(a,b);
    //   m.print();
    return 0;
}

This is the output i get on xcode console -

Question 2

You forgot the new operator (or the Malloc)

Matriz a = new Matriz(3, 2);

Question 3

The first problem is that you cant instantiate an abstract object like IMatriz, you need to change it to IMatriz* a or IMatriz& a in the following function declaration.

virtual void mult(IMatriz a, IMatriz b) = 0;

Second, the above pure virtual function is not overridden by the Matriz class, which makes the Matriz class still an abstract class. Because in the derived class, you declare it as void mult(Matriz a, Matriz b); , a different function signature as in the base class.

The solution is to change void mult(Matriz a, Matriz b); to void mult(IMatriz* a, IMatriz* b) from both the base class and the derived class and call it with the pointers.