Inheritence

Question 1

What is the syntax to declare a derived class?

Answer 1

class derived_name : access_specifier base_name

Question 2

What are the most important rules of constructor pre-initialization with base classes?

Answer 2

• The call to the base class must be called before any other constructor
• cannot be called in the class or it just creates and instance inside the class

Question 3

What are the three modes of inheritence?

Answer 3

• public
• protected
• private

Question 4

What is the default mode of inheritence?

Answer 4

private

Question 5

What happens to the members of a public base class?

Answer 5

The public base-members remain public, and the protected base-members remain protected in the derived class.

Question 6

What happens to the members of a protected base class?

Answer 6

Both public and protected base-members become protected in the derived class.

Question 7

What happens to member types in a privately inherited base class?

Answer 7

Both public and protected base-members become private in the derived class.

Question 8

What base class members do derived classes have access to?

Answer 8

Only public and protected, private is inherited but not directly accessible.

Question 9

How can a derived class access private members of a base class?

Answer 9

Through getters/setters, or if the base class friends the derived class.

Question 10

What is the essence of polymorphism?

Answer 10

The ability to store a derived class in a bass class and use all the methods of the base class.

Question 11

How is runtime polymorphism achieved in C++?

Answer 11

With base class pointers and derived class references. ex:
derived d();
base * b = &d;

Question 12

How do you tell a polymorphic object to use the derived method rather than the base method?

Answer 12

Virtual Methods

Question 13

What is the syntax to declare a virtual method?

Answer 13

virtual return_type method_name(inputs) {}

Question 14

Where are virtual methods declared?

Answer 14

In the base class

Question 15

Given class base with method virtual string print, and class derived with method string print, and object derived d (); base *btod = &d;, what method will btod->print() call?

Answer 15

The derived print method.

Question 16

Given class base with method string print, and class derived with method string print, and object derived d (); base *btod = &d;, what method will btod->print() call?

Answer 16

The base print method

Question 17

What is dynamic_cast<>()?

Answer 17

An operator used to cast data from one type to another.

Question 18

What is the syntax to use dynamic casting?

Answer 18

dynamic_cast<new_type> (expression)

Question 19

What is downcasting?

Answer 19

Casting a base class pointer to a derived class pointer.

Question 20

What is upcasting?

Answer 20

Casting a derived class reference to a base class pointer.

Question 21

What happens if you downcast an object into something that is not the type or cannot hold the object?

Answer 21

It returns a nullptr.