Why polymorphism is needed in C++ - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a base class pointer.

C++

Base* [1];

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Aobject

Bptr

Cbase

Dpointer

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that is a reserved keyword.

Forgetting the asterisk (*) for pointer declaration.

We declare a pointer named ptr to the base class Base.

2fill in blank

medium

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

C++

Derived d;
Base* ptr = [1];

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A*d

Bptr

Cd

D&d

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning the object directly without using &.

Using the pointer variable name on the right side.

We assign the address of the derived object d to the base class pointer ptr.

3fill in blank

hard

Fix the error in the virtual function declaration to enable polymorphism.

C++

class Base {
public:
    virtual void show() [1]
};

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A()

B;

C{}

Dvoid

Attempts:

3 left

💡 Hint

Common Mistakes

Ending the declaration with a semicolon only, without providing a function body.

Using parentheses instead of braces.

The virtual function must have a function body or be declared pure virtual. Here, we provide an empty body with {}.

4fill in blank

hard

Fill both blanks to call the correct overridden function using polymorphism.

C++

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

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Ashow

Bptr

Cdelete

DDerived

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a non-existent function name.

Deleting the class name instead of the pointer.

We call the show function through the base pointer to invoke the derived version. Then we delete the pointer ptr to free memory.

5fill in blank

hard

Fill all three blanks to implement polymorphism with virtual functions and base pointer.

C++

class Base {
public:
    virtual void [1]() [2]
};

class Derived : public Base {
public:
    void [3]() override {
        std::cout << "Derived show" << std::endl;
    }
};

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

Ashow

B{}

C;

Ddisplay

Attempts:

3 left

💡 Hint

Common Mistakes

Using different function names in base and derived classes.

Ending the base class function declaration with a semicolon instead of braces.

The virtual function show is declared with an empty body {} in the base class and overridden in the derived class.