PlantUMLLanguage specificationObject Diagram
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Object Diagram

Definition of objects

You define instance of objects using the object keywords. 

@startuml
object firstObject
object "My Second Object" as o2
@enduml

Relations between objects

Relations between objects are defined using the following symbols :

Type Symbol Image
Extension <|--
Composition *--
Aggregation o--

It is possible to replace -- by .. to have a dotted line.

Knowing those rules, it is possible to draw the following drawings.

It is possible a add a label on the relation, using : followed by the text of the label.

For cardinality, you can use double-quotes "" on each side of the relation. 

@startuml
object Object01
object Object02
object Object03
object Object04
object Object05
object Object06
object Object07
object Object08

Object01 <|-- Object02
Object03 *-- Object04
Object05 o-- "4" Object06
Object07 .. Object08 : some labels
@enduml

Associations objects

@startuml
object o1
object o2
diamond dia
object o3

o1  --> dia
o2  --> dia
dia --> o3
@enduml

Adding fields

To declare fields, you can use the symbol : followed by the field's name. 

@startuml

object user

user : name = "Dummy"
user : id = 123

@enduml

It is also possible to group all fields between brackets {}. 

@startuml

object user {
  name = "Dummy"
  id = 123
}

@enduml

Common features with class diagrams

Map table or associative array

You can define a map table or associative array, with map keyword and => separator. 

@startuml
map CapitalCity {
 UK => London
 USA => Washington
 Germany => Berlin
}
@enduml


@startuml
map "Map **Contry => CapitalCity**" as CC {
 UK => London
 USA => Washington
 Germany => Berlin
}
@enduml


@startuml
map "map: Map<Integer, String>" as users {
 1 => Alice
 2 => Bob
 3 => Charlie
}
@enduml

And add link with object. 

@startuml
object London

map CapitalCity {
 UK *-> London
 USA => Washington
 Germany => Berlin
}
@enduml


@startuml
object London
object Washington
object Berlin
object NewYork

map CapitalCity {
 UK *-> London
 USA *--> Washington
 Germany *---> Berlin
}

NewYork --> CapitalCity::USA
@enduml

[Ref. #307]