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Winter 2007 ACS-3913 Ron McFadyen 1
Classes
Represented by a rectangle with possibly 3 compartments
Customer
Customer
NameAddress
Customer
NameAddress
getName()checkCreditRating()
Customer
getName()checkCreditRating()
Winter 2007 ACS-3913 Ron McFadyen 2
Classes
«Singleton»dbFacade
Some classes are stereotyped:
Later in the course we study the Singleton design pattern.
Some methodologies have 3 stereotypes for “analysis” classes: boundary, control, entity
Winter 2007 ACS-3913 Ron McFadyen 3
Class Diagram
Navigability
In the example below, student could be implemented with a history attribute:
Student History *
-history[0..*] : History
history[0..*] provides for the association to be navigated – we can send a message to a History object
Winter 2007 ACS-3913 Ron McFadyen 4
Instances
Joe: Customer
Class instances
An individual object (instance of a class) is shown with naming information underlined
An unnamed customer: Customer
A customer named Joe
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Diagramming notation
:sale
s4:sale
A sale object named s4
An unnamed sale object
s4
An object named s4
Sale
The class Sale
Winter 2007 ACS-3913 Ron McFadyen 6
Attributes
an object contains data which are defined as part of the Class definition
examples:• Students have names, addresses, etc; • Courses have titles, descriptions, prerequisite information.
Rectangle
corner: Point
Student
nameaddress
Level of detail present will depend on whether you are in analysis or design, and your purposes at the time
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Attributes
To what degree is an attribute visible to other classes?Private –Public +Protected #Package ~
Student
-name-address
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Attributes
Default values =Derived values /Multiplicity [ ]Ordering {ordered}Uniqueness {unique}
Invoice
-date:Date = today-/total: Currency-payments[0..*]: Currency
Student
-name-address[1..3] {unique}
Winter 2007 ACS-3913 Ron McFadyen 9
Operations. What are the responsibilities of a class? What can it do?
Visibility
Parameters
Signature the name, parameters, and return type of the operation
Student
+getName()+getGPA(term :Term, gpaType: String)
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Associations
• correspond to verbs expressing a relationship between classes
• example a Library Member borrows a Copy of a Book
•Multiplicities• we indicate via multiplicities the range of allowable cardinalities for participation in an association• examples: 1, 1..*, 0..*, 1..3
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Associations
• Names and roles
• you can name the relationship and indicate how to read it• you can give role names for participating objects
Person CompanyWorks for1..* 1
employer employee
The role of a Person in this relationship The role of a Company in this relationship
The name of the relationship and thedirection for reading the name
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Associations
•example: a Library Member borrows a Copy of a Book
Member Book* *
borrowerborrows
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Associations
• example: An employee is supervised by an employee
*
0,1Employee
reports to
supervised
supervisor
A reflexive association
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Interfaces
An interface is special type of class that cannot be instantiated. An application can never instantiate an interface.
An interface defines a set of public attributes and operations that some class must use (depends on)
There is no behaviour defined, no method coded
Some other class inherits the interface and provides the implementation
Winter 2007 ACS-3913 Ron McFadyen 15
From Head First …
package headfirst.observer.weatherobservable;import java.util.Observable;import java.util.Observer;
public class ForecastDisplay implements Observer, …
public void update(Observable observable, Object arg) {if (observable instanceof WeatherData) {
WeatherData weatherData = (WeatherData)observable;lastPressure = currentPressure;currentPressure = weatherData.getPressure();display();
}}public void display() {
System.out.print("Forecast: ");if (currentPressure > lastPressure) {
System.out.println("Improving weather on the way!");} …
Winter 2007 ACS-3913 Ron McFadyen 16
From Head First …
package headfirst.observer.weatherobservable;
import java.util.Observable;import java.util.Observer;
public class StatisticsDisplay implements Observer, DisplayElement {private float maxTemp = 0.0f;
…public void update(Observable observable, Object arg) {
if (observable instanceof WeatherData) {WeatherData weatherData = (WeatherData)observable;float temp = weatherData.getTemperature();…
display();}
}public void display() {
System.out.println("Avg/Max/Min temperature = " …
Winter 2007 ACS-3913 Ron McFadyen 17
From Head First …
<<interface>>Observer
ForecastDisplay
update()
These classes implement the update operation
StatisticsDisplay
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Sequence Diagram
•Objects are represented horizontally across the top of the diagram
•Each object has a lifeline
•some exist before and/or after
•some are created during
•some are destroyed during
•An active object is indicated by a narrow rectangle
•Focus of control
•Time is represented vertically down the diagram. Time moves forward as you go downwards
•Iteration is shown with a frame
Winter 2007 ACS-3913 Ron McFadyen 19
Sequence Diagram
Message types
•Synchronous
•Asynchronous
•Creation
•Reply
SynchronousA message from one object to another object, and where the first object must wait until the resulting action completes.ReplyRepresents an explicit return of control. Not often used.
Winter 2007 ACS-3913 Ron McFadyen 20
: register : sale
: payment
makePayment()
makePayment()payment()
sd Make payment
Sequence Diagram named Make payment
Object is created
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X
: register : sale
: payment
makePayment()
makePayment()payment()
sd Make Payment
Object is destroyed
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Message to ‘self’
A reflexive message
: sale
calcTotal()getTotal()
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Iteration
:Sale :SalesLineItem
t=getTotal()
st = getSubTotal()loop [I < numItems]
loop is one of the keywords you can use to specify the nature of the fragment
Winter 2007 ACS-3913 Ron McFadyen 24
client
getInstance()alt
Behaviour in Singleton Pattern
:CarMatchOfficeCarMatchOffice()
Inst=CarMatchOffice()
getInstance()
[inst == null]
[else]
getAddress()
When you ask for the instance of CarMatchOffice, there are two ways it can complete. CarMatchOffice
Winter 2007 ACS-3913 Ron McFadyen 25
Collaborations
Collaboration : an arrangement of classes, links, roles in a context to implement some behaviour.
Useful for showing a system’s applications of patterns.
Name of pattern appears in a dashed oval.
Links to classes shown with participation roles.
The value of using collaborations on your class diagram is to show what patterns you have used and the roles that classes and objects will be playing.
Winter 2007 ACS-3913 Ron McFadyen 26
Weather Station Class Diagram
«interface»
Subject
attach()
detach()
notify()
«interface»
Observer
update()
WeatherDataattach()detach()notify()
CurrentConditionsDisplayupdate()display()
*
StatisticsDisplayupdate()display()
ForecastDisplayupdate()display()
«interface»
DisplayElement
display()
Winter 2007 ACS-3913 Ron McFadyen 27
Class Diagram showing Observer Collaboration
«interface»
Subject
attach()
detach()
notify()
«interface»
Observer
update()
WeatherDataattach()detach()notify()
CurrentConditionsDisplayupdate()display()
*
StatisticsDisplayupdate()display()
ForecastDisplayupdate()display()
«interface»
DisplayElement
display()
Observer
subject obse
rver
Con
cret
e su
bjec
t
Concrete observer
Concrete observer
Concrete observer
