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 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.

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 (2 nd ) 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.

General Design (2 nd ) 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.

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?