Inheritance in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is inheritance in MATLAB classes?

Inheritance allows a new class to use properties and methods from an existing class, making code reuse easier.

beginner

How do you specify a superclass in MATLAB?

You specify a superclass by using the &lt; symbol in the class definition, for example: <br> <code>classdef SubClass &lt; SuperClass</code>

intermediate

Can a subclass override a method from its superclass in MATLAB?

Yes, a subclass can provide its own version of a method, which replaces the superclass method when called on subclass objects.

beginner

What happens if a subclass does not define a method that exists in its superclass?

The subclass inherits the method from the superclass and can use it as if it were its own.

intermediate

How do you call a superclass method from a subclass in MATLAB?

Use the syntax <code>SuperClass.methodName(obj, args)</code> inside the subclass method to call the superclass version.

In MATLAB, how do you declare that class B inherits from class A?

A classdef B < A

B classdef B : A

C classdef B inherits A

D classdef B extends A

MATLAB uses the < symbol to specify inheritance in class definitions.

If a subclass does not override a method, what happens when you call that method on a subclass object?

A Superclass method is called

B Subclass method is called anyway

C Method does nothing

D Error occurs because method is missing

The subclass inherits the method from the superclass and uses it.

Which keyword is used in MATLAB to call a superclass method from a subclass?

A base

B parent

C super

D [e-mail]

MATLAB uses the syntax [e-mail] to call superclass methods.

Can a MATLAB subclass have additional properties not in the superclass?

A Only if superclass allows it

B No, it must have the same properties

C Yes, it can add new properties

D Only if properties are private

Subclasses can add new properties beyond those inherited.

What is the main benefit of using inheritance in MATLAB classes?

A To make code run faster

B To reuse code and organize related classes

C To avoid writing any methods

D To make variables global

Inheritance helps reuse code and organize related classes logically.

Explain how inheritance works in MATLAB classes and how it helps in programming.

Think about how a child inherits traits from a parent.

Describe how to override a method in a MATLAB subclass and how to call the original superclass method inside it.

Imagine changing a recipe but still using some steps from the original.

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