Inheritance in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a subclass that inherits from a superclass.

MATLAB

classdef Dog < [1]
    methods
        function bark(obj)
            disp('Woof!')
        end
    end
end

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

AAnimal

BCat

CVehicle

DTree

Attempts:

3 left

💡 Hint

Common Mistakes

Using a class that is unrelated as the superclass.

Forgetting to use the < symbol for inheritance.

The subclass Dog inherits from the superclass Animal using the < symbol.

2fill in blank

medium

Complete the code to call the superclass constructor inside the subclass constructor.

MATLAB

classdef Cat < Animal
    methods
        function obj = Cat(name)
            obj = obj@[1](name);
        end
    end
end

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

ADog

BCat

CAnimal

DVehicle

Attempts:

3 left

💡 Hint

Common Mistakes

Calling the constructor of the subclass instead of the superclass.

Forgetting to assign the result back to obj.

To call the superclass constructor, use obj = obj@Superclass(args); where Superclass is the name of the parent class.

3fill in blank

hard

Fix the error in the subclass method overriding the superclass method.

MATLAB

classdef Bird < Animal
    methods
        function sound(obj)
            disp([1]);
        end
    end
end

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

AChirp!

Bdisp('Chirp!')

Csound()

D'Chirp!'

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a string without quotes to disp.

Trying to call sound() inside itself causing recursion.

The disp function requires a string input enclosed in quotes. So use 'Chirp!'.

4fill in blank

hard

Fill both blanks to create a subclass that adds a new method and calls a superclass method.

MATLAB

classdef Fish < Animal
    methods
        function swim(obj)
            disp('Swimming');
        end
        function makeSound(obj)
            obj.[1]();
            disp([2]);
        end
    end
end

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

Asound

B'Splash!'

C'Bark!'

Dswim

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a method that does not exist.

Passing a message without quotes to disp.

The subclass calls the superclass method sound using obj.sound() and then displays 'Splash!'.

5fill in blank

hard

Fill all three blanks to override a superclass method and add extra behavior.

MATLAB

classdef Horse < Animal
    methods
        function sound(obj)
            [1]@Animal(obj);
            disp([2]);
            obj.[3]();
        end
        function neigh(obj)
            disp('Neigh!');
        end
    end
end

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

Asound

B'Whinnying!'

Cneigh

Drun

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to call the superclass method.

Not enclosing the message in quotes.

Calling a method that does not exist.

The subclass method sound calls the superclass sound method, displays 'Whinnying!', and then calls its own neigh method.

Practice

1. What does inheritance allow a subclass to do in MATLAB?

easy

A. Change MATLAB's built-in functions

B. Use properties and methods from a parent class

C. Run code without a main function

D. Create variables without declaring them

Solution

1. Step 1: Understand inheritance concept

   Inheritance means a subclass can use code from a parent class.

2. Step 2: Identify what subclass gains

   The subclass gets properties and methods from the parent class automatically.

3. Final Answer:

   Use properties and methods from a parent class -> Option B

4. Quick Check:

   Inheritance = reuse parent code [OK]

Hint: Inheritance means reuse parent class code [OK]

Common Mistakes:

• Thinking inheritance creates variables automatically
• Confusing inheritance with running code without main
• Believing inheritance changes built-in MATLAB functions

2. Which of the following is the correct way to declare a subclass Dog that inherits from superclass Animal in MATLAB?

easy

A. classdef Dog inherits Animal

B. classdef Dog : Animal

C. classdef Dog extends Animal

D. classdef Dog < Animal

Solution

1. Step 1: Recall MATLAB inheritance syntax

   MATLAB uses < symbol to indicate inheritance in classdef.

2. Step 2: Match correct syntax

   The correct syntax is classdef Dog < Animal.

3. Final Answer:

   classdef Dog < Animal -> Option D

4. Quick Check:

   Inheritance uses < in MATLAB [OK]

Hint: Use < to inherit in MATLAB classdef [OK]

Common Mistakes:

• Using 'inherits' keyword instead of <
• Using ':' or 'extends' which are not MATLAB syntax
• Confusing MATLAB syntax with other languages

3. Consider the following MATLAB code:

classdef Animal
    methods
        function sound(obj)
            disp('Some sound')
        end
    end
end

classdef Dog < Animal
    methods
        function sound(obj)
            disp('Bark')
        end
    end
end

myPet = Dog();
myPet.sound();

What will be the output when running myPet.sound()?

medium

A. Error: Method not found

B. Some sound

C. Bark

D. No output

Solution

1. Step 1: Understand method overriding in subclass

   The subclass Dog defines its own sound method, which replaces the superclass method.

2. Step 2: Determine which method runs

   Calling myPet.sound() runs the Dog version, printing 'Bark'.

3. Final Answer:

   Bark -> Option C

4. Quick Check:

   Subclass method overrides superclass method [OK]

Hint: Subclass method overrides superclass method [OK]

Common Mistakes:

• Expecting superclass method output
• Thinking both methods run
• Assuming error due to overriding

4. What is wrong with this MATLAB subclass definition?

classdef Cat <
    methods
        function meow(obj)
            disp('Meow')
        end
    end
end

medium

A. Missing superclass name after <

B. Method name cannot be 'meow'

C. Classdef keyword is misspelled

D. No constructor defined

Solution

1. Step 1: Check inheritance syntax

   The symbol < must be followed by the superclass name.

2. Step 2: Identify missing superclass

   Here, no superclass name is given after <, causing syntax error.

3. Final Answer:

   Missing superclass name after < -> Option A

4. Quick Check:

   Inheritance requires superclass name after < [OK]

Hint: Always specify superclass name after < [OK]

Common Mistakes:

• Leaving out superclass name after <
• Thinking method names cause error
• Assuming constructor is mandatory

5. You have a superclass Vehicle with a method move() that prints 'Moving'. You want to create a subclass Car that inherits Vehicle but adds a new method honk() that prints 'Beep!'. Which of the following is the correct MATLAB code for the subclass Car?

hard

A. classdef Car < Vehicle
methods
function honk(obj)
disp('Beep!')
end
end
end

B. classdef Car inherits Vehicle
methods
function honk(obj)
disp('Beep!')
end
end
end

C. classdef Car : Vehicle
methods
function honk(obj)
disp('Beep!')
end
end
end

D. classdef Car extends Vehicle
methods
function honk(obj)
disp('Beep!')
end
end
end

Solution

1. Step 1: Use correct inheritance syntax

   MATLAB uses < to inherit, so classdef Car < Vehicle is correct.

2. Step 2: Add new method in subclass

   The method honk is added inside methods block correctly.

3. Final Answer:

   classdef Car < Vehicle with honk method -> Option A

4. Quick Check:

   Subclass syntax + new method = classdef Car < Vehicle methods function honk(obj) disp('Beep!') end end end [OK]

Hint: Use < and add methods block for new methods [OK]

Common Mistakes:

• Using 'inherits', ':', or 'extends' instead of <
• Forgetting to add methods block
• Trying to override without correct syntax