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Class Diagram Viewer

Create diagrams to investigate class details and hierarchies

Since R2021a


The Class Diagram Viewer app enables you to create diagrams that show class implementation details and hierarchies. You can use this app to explore class structures and share class diagrams with others. These diagrams can include details about:

  • The internal structure of classes, including properties and methods and their access attributes

  • The hierarchy of classes, including packages, with inheritance relationships

You can create class diagrams using the graphical interface or the command line API defined by matlab.diagram.ClassViewer.

Class Diagram Viewer app

Open the Class Diagram Viewer

  • MATLAB® Toolstrip: On the Apps tab, under MATLAB, click the app icon.

  • MATLAB command prompt: Enter matlab.diagram.ClassViewer


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Open the Class Diagram Viewer. In the Class Browser pane, expand the Import Class, Folder, or File button and select Import Package. Enter matlab.unittest as the package name and click OK. The folder for unittest appears in the Class Browser.

Class Browser with unittest added

Expand the unittest folder and select the InteractiveTestCase class. Click the Add button in the toolbar to add a card for the class to the Class Diagram Viewer canvas. Add the TestCase class using the same method. Because TestCase is the superclass of InteractiveTestCase, Class Diagram Viewer automatically draws an arrow from InteractiveTestCase to TestCase to show this relationship.

TestCase and InteractiveTestCase classes on canvas

The striped blue borders at the top of the class cards indicate that both of these classes are handle classes. The Legend pane describes what the graphic effects and icons on the canvas represent.

Legend pane

You can also drag and drop items from the Class Browser directly to the canvas. Drag and drop the Test class to the viewer. The green plus button at the top of the card indicates that Test has a viewable superclass.

Test class card with green plus button

Click the green plus button to add the superclass to the diagram. The arrow pointing to TestSuite from Test indicates that TestSuite is a superclass of Test.

Test and TestSuite class icons

In addition to moving the classes in the viewer by dragging and dropping, you can customize the view using the options in the Zoom and Pan section of the toolbar, including:

  • Zoom in and out

  • Fit the model to the current screen size

  • Pan

In the View section, select the Mixins check box. This action does not automatically add mixin classes to the diagram, but going forward, the viewer adds them to the display when you perform any action that adds superclasses.

To add all the superclasses of Test, right-click the Test class card and select Add All Superclasses. The CustomDisplay mixin now appears as a superclass of Test, and TestSuiteExtension appears as a superclass of TestSuite. The name of CustomDisplay is italicized, indicating that it is an abstract class.

CustomDisplay mixin and TestSuiteExtension visible

You have two options each for adding superclasses and subclasses:

  • Add Superclasses: Add superclasses that the given class inherits directly from.

  • Add All Superclasses: Add all superclasses that the given class inherits directly or indirectly from. In the example above, Test indirectly inherits from TestSuiteExpansion.

  • Add Subclasses: Add known subclasses that inherit directly from the given class.

  • Add All Subclasses: Add all known subclasses that inherit directly or indirectly from the given class.


MATLAB might not identify all existing subclasses of a given class. In that case, use the Class Browser to add any additional subclasses manually.

In addition to relationships between classes, you can also explore the class definitions themselves. Expand the Test class card by clicking the arrow next to the class name in its card. The class card expands to show the properties and methods defined by the class. Properties and methods inherited from superclasses do not appear in the subclass cards.

The icons next to the property and method names identify the access levels of the properties and methods. For example, the lock icon shows that ExternalFixtures is a private property.

Test class card with properties visible

Selecting a property or method on the class card also displays access and other information in the Inspector pane.

To view the source code of one or more classes, select their cards and click Go To Source in the toolbar. The source code files open in the MATLAB Editor.

To save or share your diagram, use one of two options:

  • Click Export to save the diagram as a static image.

  • Select Save > Save as to create an MLDATX file that can be reopened in a Class Diagram Viewer instance and edited.

Programmatic Use

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matlab.diagram.ClassViewer opens a Class Diagram Viewer instance with no classes loaded.

matlab.diagram.ClassViewer(Name,Value) adds the specified classes to both the Class Browser pane and the canvas. Valid name-value arguments include:

  • Classes, with class names specified as strings or object names

  • Folders, with folder names specified as strings

  • Packages, with package names specified as strings

See matlab.diagram.ClassViewer for additional name-value arguments. Specify arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value.


  • Class Diagram Viewers are instances of the matlab.diagram.ClassViewer class. Use the class constructors to open more than one viewer at a time.

  • When green plus button appears on an arrow between two classes, rather than on a class card itself, there are additional classes in the hierarchy between the two connected classes. Click green plus button to add all of the viewable classes in that part of the hierarchy.

  • If you make changes to the class code while using the Class Diagram Viewer, you can automatically update the diagram by clicking Refresh.

Version History

Introduced in R2021a

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