Object-Oriented Programming Introduction toUML Class Diagrams

CSIE Department, NTUT

Woei-Kae Chen

UML: Unified Modeling LanguageSuccessor to OOA&D methods

late 1980s and early 1990sUnifies

Jacobson & OMT (Booch & Rumbaugh)Graphical notation used to express designs

Use casesClass diagramsInteraction diagrams

Sequence diagramsCollaboration diagrams

Package diagramsState diagramsActivity diagramsDeployment diagrams

GoF Book

UML class diagrams

Three perspectivesConceptual

represents of the domain under studyrelate to the class that implement them, but often no direct mapping

Specificationlooking at types rather than classesa type represents an interface that may have different implementations

Implementationlooking at classes for our OOP class

UML: a class

+ public# protected- private

AbstractConcrete

•data type•parameter

Example: OBSort1.cpp

Example: OBSort1.cpp

Let’s assume main() is a class

relationship

UML: class relationshipAssociation (knows a)Dependency (uses a)Composition (has a)Aggregation (has a)

Inheritance (is a)

Class templateXY

X Y

X Y

X Y

X Y

Y

X

(parameterizedclass)

“Uses a” “Knows a” relationship

“Uses a”DependencyOne object issues a function call to a member function of another object

“Knows a”AssociationOne object is aware of another; it contains a pointer or reference to another object

X Y

X Y

“Is a” “Has a” relationship

“Is a” relationshipsInheritancea class is derived from another class

“Has a” relationshipsComposition or Aggregationa class contains other classes as members

X

Y

X Y

X Y

Aggregation Composition

Both are “Has a” or “part-of” relationshipComposition

a stronger variety of aggregationthe part object may belong to only one wholeexpected to live and die with the whole

delete whole delete partAggregation

cascading delete is oftenan aggregated instance can be shared

X Y X Y

Example: “has a” relationship

Multiplicity

a Point may appear in only one Polygon or Circle

a Style may be shared by many Polygons and Circles

Delete Polygon delete PointDelete Polygon delete StyleX

UML Example (C++): AssociationX Y

class X {

X(Y &y) : y_ref(y) {}

void SetY(Y *y) {y_ptr = y;}

void f() {y_ptr->doIt();}

...

Y *y_ptr; // pointer

Y &y_ref; // reference

};

UML Example (C++): Dependency

X Y

class X {

...

void f1(Y y) {...; y.doIt();}

void f2(Y *y_ptr);

void f3(Y &y_ref);

};

Example: OBSort3.cpp

uses•getSize()•operator[]

UML Example (C++): Composition 1

class X {

...

Y a; // 1; Composition

Y b[10]; // 0..10; Composition

vector<Y> c; // ??

};

X Y

Composition of vector<Y>

NOT Composition of Y

Java?

UML Example (C++): Composition 2

class X {

X() { a = new Y[10]; }

~X(){ delete [] a; }

...

Y *a; // 0..10; Composition

};NOT Association

X Y

UML Example: OBSort3.cpp

UML Example (C++): Aggregation 1

class X {X() { a = new Y[10]; }~X(){ delete [] a; }

...Y *a; // 0..n; Aggregationvector<Y> b;// Y’s are instantiated

// and destroyed by X};

X Y

May be considered as aggregation of Y

The same as composition?

UML Example (C++): Aggregation 2

class X {...vector<Y> b;

};

X vector<Y> Y

X Y

Hiding implementation detail

Implementation detail

UML Example (C++): Inheritance

class Y {...};

class X : public Y {...};

X

Y

“is a” relationship

Example: OOSort2.cpp

UML Example (C++):Template Class

template <class T>

class X {

...

...

...

};

XY

...

X<Y> a;

...

Abstract class

C++ static member