Object Oriented Design Peter McClone. Goals To be able to: Identify how an object contributes to a...

Object Oriented Design

Peter McClone

Goals

To be able to: Identify how an object contributes to a problem

solution Identify what classes are needed to solve a problem Describe how objects work together to solve a

problem Group objects with similar attributes into one class Distinguish between instances and classes Draw the object diagram for a description given

Location: Mootown Airport

Mootown is a small city in rural Wisconsin. The Mootown City Council has started discussions about building an airport.

The Mootown City Council contracted with C. Thomas Wu Consulting Inc. to design a computer model of the airport. The City Council has a general description of the initial airport design from which we will base our design.

General Design The airport is small. It has one runway and two ticket counters. Each ticket counter controls two gates where passengers can board

their flights. Each gate can only support one airplane at a time. Passengers enter the airport, go to a ticket counter to check-in,

surrendering a ticket to a ticket counter employee and receiving back a boarding pass. After receiving a boarding pass, they go to a gate where they wait.

When the airplane is ready, the passengers board their flight. When all of the passengers have boarded, the airplane taxis away from the gate to the runway, where it will take off to travel to Corntown airport in Iowa, Wheattown airport in Kansas, and/or Beettown airport in Minnesota.

Ticket Counter #1 serves Gurnsey Express and Ticket Counter #2 serves Holstein Airways. Ticket Counter #1 has two Gates, Gate A and Gate B.

Ticket Counter #2 controls Gate C and Gate D. The two Ticket Counters also have various employees working at them. Jennifer and Jim both work at Ticket Counter #1; Tom and Theresa work at Ticket Counter #2.

Pulling out the nouns: The airport is small. It has one runway and two ticket counters. Each ticket counter controls two gates where passengers can board






Creating the model

Our Nouns: Runway, Ticket Counter, Gate, Passenger, Flight, Airplane, Employee,

Ticket, Boarding Pass Each noun in this list will be a class in our model of the Mootown

Airport. Each of these classes will have one or more instances (also called

objects) in our model. Example:

Class: Employee Instance: Tom, Theresa, Jim, Jennifer Class: Ticket Counter Ticket Counter #1, Ticket Counter #2

Leaving things out

What are we missing? Plants, carpet, air … etc.

Only include what is necessary for our model. Careful consideration must be given to what is

needed to obtain a solution to the given problem AND what may be needed to solve future, similar problems.

There are situations where a lot of detail is needed

Data Members

What sort of information is it important to associate with each class?

Let’s go through each class

Runway

length - number of meters

direction - the compass heading the runway faces (north, south, etc.)

Ticket Couner

airline - name of the airline the ticket counter serves

employees - number of employees working at the counter

gates - number of gates the ticket counter controls

Gate

plane - the flight number of the plane currently outside, if there is one

name – the name of the gate

Passenger

name - the passenger's first and last name ticket – a ticket for his/her flight boardingPass - a boarding pass for

his/her flight

Flight

airline - name of the airline the flight belongs to

number - flight number that identifies what flight it is

destination - the flight's next stop departure - time the flight is scheduled to

leave arrival - time the flight is scheduled to land

at its destination

Airplane

type - what kind of plane it is (Example: 747)

airline - what airline it belongs to capacity - the number of people that the

plane can hold

Employee

name - first and last name IDNumber - identification number

Ticket

planeNumber - what plane the ticket is for rowNumber - what on the plane the ticket

is for seatNumber - what seat the ticket is for

Boarding Pass

name - name of the passenger who holds it

gate - gate the pass is for

General Design (2nd) The airport is small. It has one runway and two ticket counters. Each ticket counter controls two gates where passengers can board






What isn’t mentioned?

Land - Airplane makes contact with the runway, slows down, and eventually stops

Others?

What action belongs to what class?

Runway

Data members: Length – number of meters direction - the compass heading the runway

faces (north, south, etc.) Methods:

None

Ticket Couner

Data members: airline - name of the airline the ticket counter

serves employees - number of employees working at

the counter gates - number of gates the ticket counter

controls Methods:

None

Gate

Data Members: plane - the flight number of the plane currently

outside, if there is one name – the name of the gate

Methods: None

Passenger

Data Members: name - the passenger's first and last name ticket – a ticket for his/her flight boardingPass - a boarding pass for his/her flight

Methods: enterAirport - proceed through the door to the airport

facility wait - sit, stand, or pace until the correct boarding call is

announced surrenderTicket - give a ticket to an airport employee goToGate - proceed to the gate indicated on a boarding

pass boardPlane - get on the plane

Flight

Data Members: airline - name of the airline the flight belongs to number - flight number that identifies what flight it is destination - the flight's next stop departure - time the flight is scheduled to leave arrival - time the flight is scheduled to land at its

destination

Methods: None

Airplane

Data Members: type - what kind of plane it is (Example: 747) airline - what airline it belongs to capacity - the number of people that the plane can hold

Methods: taxi - plane moves from the gate to the start of the

runway takeOff - plane accelerates down the runway and lifts

off the ground land - plane makes contact with the runway and

decelerates until it reaches the end of the runway

Employee

Data Members: name - first and last name IDNumber - identification number

Methods: receiveTicket - obtain a ticket from a

passenger and give a boarding pass

Ticket

Data Members: planeNumber - what plane the ticket is for rowNumber - what on the plane the ticket is

for seatNumber - what seat the ticket is for

Methods: None

Boarding Pass

Data Members: name - name of the passenger who holds it gate - gate the pass is for

Methods: None

Diagrams

Diagrams (cont.)

Summary

Understanding the problem and designing a solution can save you much time during the implementation

Modular and language independent design are part of the principles of OOP

Questions?

Object Oriented Design Peter McClone. Goals To be able to: Identify how an object contributes to a...

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