Base class pointers in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a base class pointer.

C++

Base* [1];

Drag options to blanks, or click blank then click option'

AbasePtr

Bobj

Cpointer

Dptr

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that is not a pointer.

Forgetting the asterisk (*) to declare a pointer.

The pointer to the base class is declared as 'basePtr' here, which is a common naming convention.

2fill in blank

medium

Complete the code to assign the address of a derived class object to a base class pointer.

C++

Derived d;
Base* ptr = [1];

Drag options to blanks, or click blank then click option'

A&d

Bd

Cptr

D*d

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning the object itself instead of its address.

Using the pointer variable name instead of the object.

We assign the address of the derived object 'd' to the base class pointer using '&d'.

3fill in blank

hard

Fix the error in the code to correctly call the base class function using a base class pointer.

C++

Base* ptr = new Derived();
ptr->[1]();

Drag options to blanks, or click blank then click option'

AderivedFunction

BbaseFunction

CDerivedFunction

DBaseFunction

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to call a derived class specific function through a base class pointer.

Using incorrect capitalization for function names.

The base class pointer can only call functions declared in the base class, so 'baseFunction' is correct.

4fill in blank

hard

Fill both blanks to create a base class pointer that points to a derived class object and calls a virtual function.

C++

Base* [1] = new Derived();
[2]->virtualFunction();

Drag options to blanks, or click blank then click option'

Aptr

BbasePtr

CderivedPtr

DobjPtr

Attempts:

3 left

💡 Hint

Common Mistakes

Using different pointer names in declaration and call.

Calling non-virtual functions expecting polymorphic behavior.

The pointer 'basePtr' is used to point to the derived object and call the virtual function correctly.

5fill in blank

hard

Fill all three blanks to correctly delete a derived class object through a base class pointer and avoid memory leaks.

C++

Base* [1] = new Derived();
// ... use the object
delete [2];
[3] = nullptr;

Drag options to blanks, or click blank then click option'

Aptr

BbasePtr

CderivedPtr

DobjPtr

Attempts:

3 left

💡 Hint

Common Mistakes

Deleting using a different pointer than the one used to allocate.

Not setting the pointer to nullptr after deletion.

Deleting the object through the base class pointer 'basePtr' and setting it to nullptr prevents memory leaks.