Interface-like behavior in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a pure virtual function in a C++ class.

C++

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

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

A= 0

B{}

C;

D()

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the = 0 and just ending with a semicolon.

Adding an empty function body instead of making it pure virtual.

In C++, a pure virtual function is declared by assigning = 0 at the end of the function declaration.

2fill in blank

medium

Complete the code to override the pure virtual function in the derived class.

C++

class Circle : public Shape {
public:
    void draw() [1] {
        // drawing code
    }
};

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A() override

B()

C(int)

D(void)

Attempts:

3 left

💡 Hint

Common Mistakes

Changing the function parameters.

Forgetting to add override keyword.

When overriding a virtual function, use the same signature and add override to indicate it overrides a base class method.

3fill in blank

hard

Fix the error in the code to prevent instantiation of the abstract class.

C++

Shape s[1];

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A[]

B;

C{}

D()

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to create an object of an abstract class.

Not using pointers or references for abstract types.

You cannot create an object of an abstract class. The error is trying to instantiate Shape with parentheses. To fix, remove the instantiation or use a pointer/reference.

4fill in blank

hard

Fill both blanks to declare an interface-like class with a pure virtual destructor.

C++

class Interface {
public:
    virtual ~Interface() [1];
    virtual void execute() [2];
};

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A= 0

B{}

C;

D()

Attempts:

3 left

💡 Hint

Common Mistakes

Not declaring the destructor as pure virtual.

Forgetting to provide a destructor body if pure virtual.

To make a class interface-like, declare all functions, including the destructor, as pure virtual by using = 0.

5fill in blank

hard

Fill all three blanks to implement a derived class overriding interface methods correctly.

C++

class Impl : public Interface {
public:
    ~Impl() [1] override [2] {
        // destructor code
    }
    void execute() [3] override {
        // execution code
    }
};

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

A()

B{}

C;

D(void)

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting function bodies.

Using semicolons instead of braces for function definitions.

Destructor and methods must have matching signatures and bodies. Use () for parameters and {} for function bodies.