Week 5

Question 1

What is object orientated programming

Answer 1

It is a programming paradigm based on concept of objects which are instances of classes

Objects contain:
data - attributes / properties
code - methods / functions

Question 2

What is Object-Orientated design

Answer 2

process of designing a software solution using OOP

Question 3

what are method signatures

Answer 3

Each method has signature : name, parameters, return type and access level.

Question 4

What are key ideas related to object calling and answering

Answer 4

objects interact by calling methods, but not just any, only predefined methods

They don’t accept arbitrary calls
Methods define acceptable calls

Question 5

What is an object interface

Answer 5

This is the set of method signatures available for the object

example arrays have .index or .get or whatever but you don’t actually know wtf happens behind the interface.

Question 6

explain information hiding or encapsulation regarding Object interfaces

Answer 6

Involves hiding their internal attributes and only allowing access through interface methods.

Question 7

client and server objects

Answer 7

client = object requesting something
server = the object fulfilling it by like doing the function

scenario based obvs

when object calls a method on another object its like sending a message “ hey poes do this”

Question 8

Modules vs objects

Answer 8

modularity is more for just organising code by grouping functionality together

objects is similar but encapsulates data

Question 9

What are UMLs

Answer 9

• Unified Modelling Language

Standardised visual language which represents different aspects of a systems structure and behaviour

similar to ERDs

Question 10

Key components of a UML

Answer 10

Class diagrams

Use case diagrams

Sequence diagrams

Activity diagrams

State machine diagrams

Component Diagrams

Deployment diagrams

Package diagrams

Question 11

UML classes has 3 compartments

Answer 11

Class Name
Attributes
Operations

Question 12

symbols with operations in UML classes

Answer 12

+ public - Accessible from anywhere (any class can use it).

• private - Only accessible within the class itself (not from other classes).

protected # - Accessible from the same class and subclasses (but not outside them).

~ package - Accessible only within the same package/module (used in Java, not in Python).

/ derived - Represents a calculated (not stored) attribute.

Question 13

class diagrams

Answer 13

shows classes, attributes and relationships

Question 14

use case diagrams

Answer 14

different users

Question 15

sequence diagrams

Answer 15

how objects interact over time
e.g. log into ATMs, requests verification, bank responds

Question 16

Activity diagrams

Answer 16

shows flow of activities in a system

like online order has
Add to cart
Payment info
Confirm order

Question 17

State machine diagrams

Answer 17

show how objects move between states

robot go red to green to yellow

Question 18

Component diagrams

Answer 18

shows software components and their dependencies

web app with its databases, UI and APIs

Question 19

Deployment diagrams

Answer 19

how software is deployed

Question 20

Package diagrams

Answer 20

groups classes into packages for better organisation

a large e commerce might have separate packages for User management or payments or order processing etc

Question 21

UML notation for classes relationships

Answer 21

Association : solid line >
Inheritance : solid line open triangle
implementation : dotted line open triangle
dependency: dotted line >
aggregation : solid line open diamond
Composition : solid line solid diamond

Question 22

what is association

Answer 22

when object accesses another in some way

owner feeds dog

bidirectional - solid line no arrow
unidirectional - solid line with one arrow
prohibited association - solid lines with two arrows facing each other

Question 23

Inheritance

Answer 23

object inherits properties of another

“is a “ relationship

Question 24

composition

Answer 24

object references another object
“has a” relationship

Question 25

aggregation

Answer 25

similar to composition composition is more child cannot exist without the parent aggregation is child can exist without parent

Question 26

inheritance vs composition in making changes

Answer 26

when you inherit you take all properties so changes in parent affect all children with composition a class contains an instance of another class so changes in one don't affect the other car has engine .

Question 27

What is polymorphism

Answer 27

its a concept in OOP allowing objects of different types or classes to be treated under a common superclass We can write code to work with objects of different classes in a uniform way even if they may behave differently

Question 28

Compile time polymorphism

Answer 28

s when compiler decides which method to use aka Static or early binding Done by method loading - methods with same names but different parameters or even done by operator overloading -operators like + * - can be overloaded to work with custom types exampling adding two fags to make a bigger fag.

Question 29

Runtime polymorphism

Answer 29

Decision about which method to call is determined during execution of the program done by: Method overriding: child redefines a method that is defined by its parent interface implementation - different classes implement the same interface but with their own implementation dog bark and cat moos

Question 30

Duck Typing?

Answer 30

form of polymorphism This is where an objects type or class is not as important as the methods it has so if the objects have methods that are expected, it is treated as the type expected even if it doesn't explicitly inherit from that type. Imagine you have different animals, like a Duck, a Dog, and a Cat. You don’t care what type of animal they are, as long as they can walk and quack ( make sounds). So, if you see an animal that walks and quacks, you treat it like a Duck, even if it's actually a Dog or a Cat. The important thing is what it can do (walk and quack), not what type of animal it is.

Question 31

Subtyping polymorphism

Answer 31

child inherits from parent so a child object can be used wherever a parent it used as it has the same attributes.

Question 31

Ad-hoc polymorphism

Answer 31

This is method or operator overloading such as compile time poly.

Question 32

poly pros and cons

Answer 32

PROS: code reusability - generic code can work with different object types modularity - able to extend functionality without changing existing code flexibility - can interact with different types without knowing the exact types CONS: complexity readability performance - dynamic dispatch is slower

Question 33

Why we use object orientated (pros)

Answer 33

Modularity and reusability make development: - Easier - Faster - More productive - Cheaper - easier to maintain * However, can be complicated to design and explain

Question 34

How do design OO systems well

Answer 34

Agility (like the scrum process) Traceability Testability - TDD Measurability - stats, reports performance Security