Error while accessing derived class resources by base class object - c++

Question

I have base class called Base and a derived class of Base called Derived,
A Base Class pointer can point to a derived class object and can also access its resource but I am getting an error doing the same.
class Base
{
public:
int a;
};
class Derived : public Base
{
public:
float b;
void DoSomething()
{
cout<<"Derived";
}
};
int main()
{
Base * pBase = new Derived();
pBase->DoSomething();
pBase->a = 5;
pBase->b = 0.2f;
return 0;
}
This gives me an error
main.cpp: In function ‘int main()’:
main.cpp:34:25: error: ‘class Base’ has no member named ‘DoSomething’
pBase->DoSomething();
^
main.cpp:36:12: error: ‘class Base’ has no member named ‘b’
pBase->b = 0.2f;
^
Pardon me if its too basics, I am a beginner in c++

Answer 1

Yes you can use a Base pointer to a Derived class, nonetheless, the Base pointer must know the methods in order to choose what's the most suited for the call, if the Base pointer has no knowledge of the existence of these variables and functions it cannot call them.
Corrected code:
class Base
{
public:
int a;
float b;
virtual ~Base(){} //virtual destructor required
virtual void DoSomething() //implementing DoSomething in base class
{
std::cout << "Base";
}
};
class Derived : public Base
{
public:
void DoSomething() override //override DoSomething() in base class
{
std::cout<<"Derived";
}
};
Base * pBase = new Derived();
//Base will choose the most suited DoSomething(), depending where it's pointing to
pBase->DoSomething();
pBase->a = 5;
pBase->b = 0.2f;
Output:
Derived
Edit:
As you suggested in the comment section, casting the derived class will work in this specific case, but it usually reveals poorly designed code, as pointed out by #user4581301's comment, also note the link provided that has some of the reasons why this is not the best idea.
As I said, if you must do it, use dynamic_cast<>() instead.
Note that, in any case, you still need the virtual destructor for a correct implementaion of polymorphism.
Virtual destructors
Deleting an object through pointer to base invokes undefined behavior unless the destructor in the base class is virtual.
and that's not all, check this link.