Object Diagram

Definition of objects

You define instance of objects using the object keywords.

@startuml
object firstObject
object "My Second Object" as o2
@enduml
simple UML object diagram

Relations between objects

Relations between objects are defined using the following symbols :

Extension<|--
Composition*--
Aggregationo--

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
UML object diagram with relationship

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
adding data and fields to UML object diagram
It is also possible to ground between brackets {} all fields.
@startuml

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

@enduml
example of object with several fields

Common features with class diagrams