Communicating Class Design

Could use text
Could use code
UML Class Diagram shows an overview of essential classes in a system and (more importantly) the relationship between them

UML Diagrams

UML Class

A static, structure diagram
Name
Attributes - data members, fields
Operations - methods, member functions

Role of Classes

Classes represent the parts of the program
They are entities, not actions
PascalCase, e.g., Project, UndergraduateStudent
Operations are the actions of the class
Like free functions, they are in the verbTarget form
camelCase typically used (at model level)

Multiple Views

Visibility

+ public
- private
# protected
~ package

UML Primitive Types

Integer
UnlimitedNatural
Real
Boolean
String

Attributes: visibility name:type multiplicity = default {property-string}

Attribute Syntax	Description
`+name`	public name
`-name`	private name
`-name:Name`	private name of type Name
`-name:Name = "Project"`	private name of type Name with default "Project"
`-name:Name[3]`	private name of type Name with multiplicity of 3
`-name:Name = "Project" { persistent }`	private name of type Name with the default "Project", and property 'persistent'

Operations: visibility name(parameter-list):return-type {property-string}

Operator Syntax	Description
`+draw()`	public operator draw()
`-draw()`	private operator draw()
`#draw()`	protected operator draw()
`+draw() : Boolean`	public operator draw() with return type Boolean
`+draw() : Boolean {optional}`	public operator draw() with return type Boolean, and a property optional

Operation Parameters: direction name:type = default

Parameter Syntax	Description
`+draw(: Shape)`	parameter of type Shape
`+draw(s: Shape)`	parameter s of type Shape
`+draw(in shape : Shape)`	in parameter shape of type Shape
`+draw(out picture : Picture)`	out parameter picture of type Picture
`+draw(inout picture : Picture)`	inout parameter picture of type Picture

Directions: in, out, inout

Parameter Directions in C++

C++ Declaration	UML Parameter Direction
Shape	in
const Shape&	in
const Shape*	in
Shape&	inout
Shape*	inout
Shape**	out (typical API usage)

Multiplicity

Multiplicity Syntax	Description
`*`	Any number of values
`1`	Single value (default)
`0..1`	No more than a single value
`2..4`	Two to four values

Multiplicity Terms

Multiplicity Term	Description
Optional	`*`
Mandatory	`1..*`
Single-valued	`0..1`
Multivalued	`0..2`, `0..*`

Mapping Multiplicity to C++

Multiplicity	Standard C++ Data Structures
Multivalued	`std::vector<int>`, `std::deque<int>`, `std::list<int>`, `std::array<int, n>`
Single-valued	`std::optional<int>` (C++14)

Guidelines

Attributes show the state of the objects and may not map directly into types in the implementation language
Show only the attributes and operations (methods) important for the given purpose
Public attributes typically map to get and set (stereotype) methods in the code
Only display constructors if needed

Properties: Attributes & Association

Another notation for property (alternative to attribute)
Use attributes for properties that are data types, e.g., primitive types or whatever is considered a data type in your design
Use associations for class types, especially if the methods are of interest at the design level
Is String a class or a datatype?

DataType	Class
Primitives	Objects
Methods are familiar	Methods are not familiar
Operators do not change	Operators can change
New developers know exactly what you mean	New developers have only a vague idea
Tend to be scalar (single value)	Tend to be complex types
Equivalent values ⇨ same identity	Two distinct objects can have the same value
Probably not a base for generalization (inheritance)	Maybe a base for generalization (inheritance)

Stereotypes

stereotype is an extension mechanism to UML used as part of profiles
keyword is a formally defined stereotype
CBE - Control, Boundary, Entity

Qt

Notes

Use text to clarify diagram/design
The UML "comment" mechanism
No formal definition of note content

Guidelines

Attributes show the state of the objects and may not map directly into types in the implementation language
Show only the attributes and operations (methods) important for the given purpose
Public attributes typically map to get and set (stereotype) methods in the code
Only display constructors if needed

Forward Engineering

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Reverse Engineering

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