How to draw a UML class diagram

A class diagram shows the types in a program, what they hold and do, and how they relate. Draw one to design or explain code structure.

Step by step

1. Pick UML class from the Diagram menu, click Class, then click the board. Type the name, then one member per line: attributes, and operations with parentheses, like +signIn().

   

2. Add the other classes the same way. Each one grows to fit its members.

   

3. Pick a relation and drag from one class to the other: Inheritance from the child to the parent, Composition and Aggregation from the part to the whole.

   

Tips

• Show the members that matter for the question, not every field.
• Use + for public and - for private, as UML does.
• Mark an abstract class or an interface in its name, like «interface» Shape.

Mermaid

Paste this onto the board, or use Board menu → Import Mermaid…; Export Mermaid… writes a board back as text.

classDiagram
  class User {
    -String email
    +signIn()
  }
  User <|-- Customer
  User <|-- Admin
  Customer --> Order : places

Relations: <|-- inheritance, <|.. realization, *-- composition, o-- aggregation, --> association, ..> dependency, -- and .. links. More on Mermaid import and export.