Why abstraction is required in C++ - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an abstract class with a pure virtual function.

C++

class Shape {
public:
    virtual void draw() = [1];
};

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A0

B1

Ctrue

Dvoid

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of 0 for pure virtual function

Omitting the virtual keyword

Trying to define the function body here

In C++, a pure virtual function is declared by assigning 0 to it. This makes the class abstract.

2fill in blank

medium

Complete the code to create a pointer to the abstract class and assign it to a derived class object.

C++

Shape* shape = new [1]();

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AShape

BObject

CRectangle

DCircle

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to instantiate the abstract class directly

Using a class that does not implement all pure virtual functions

You cannot create an object of an abstract class directly, but you can create a pointer to it and assign it to a derived class object like Circle.

3fill in blank

hard

Fix the error in the code by completing the missing keyword to enforce abstraction.

C++

[1] Shape {
public:
    virtual void display() = 0;
};

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Aclass

BAbstract

CInterface

DConcrete

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'abstract' or 'interface' keywords which do not exist in C++

Omitting the 'class' keyword

In C++, classes are declared with the keyword 'class'. There is no special keyword 'abstract' or 'interface'. Abstraction is enforced by pure virtual functions.

4fill in blank

hard

Fill both blanks to define a derived class that implements the pure virtual function.

C++

class Circle : public Shape {
public:
    void [1]() override {
        std::cout << "Drawing Circle" << std::endl;
    }
};

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Apaint

Bdisplay

Cdraw

Dshow

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name than the base class

Omitting the override keyword

The derived class must implement the pure virtual function 'draw' declared in the base class Shape.

5fill in blank

hard

Fill all three blanks to create an abstract class and a derived class that implements its pure virtual function.

C++

class [1] {
public:
    virtual void [2]() = 0;
};

class [3] : public [1] {
public:
    void [2]() override {
        std::cout << "Implemented" << std::endl;
    }
};

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

AShape

Bdraw

CCircle

DObject

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching class or function names

Not implementing the pure virtual function in the derived class

The abstract class is Shape with a pure virtual function draw. The derived class Circle implements draw.