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Class Diagram Viewer

Create diagrams with class details and hierarchies

Since R2021a

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Description

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 namespaces, 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.

Examples

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Open the Class Diagram Viewer. In the Class Browser pane, expand the Import Class, Namespace, or Folder button and select Import Namespace. Enter matlab.unittest as the namespace 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 toolstrip 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 items from the Class Browser directly to the canvas. Drag 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 cards

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 toolstrip, including:

  • Zoom in and out

  • Fit the diagram to the current screen size

  • Pan

In the View section of the toolstrip, 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 class cards are 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.

Note

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 displaying class hierarchies, 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 toolstrip. 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.

Since R2024a

The Class Diagram Viewer can show associations between classes. When the type of a class property is explicitly defined as another class using class validation, the Class Diagram Viewer can show this association.

Save these two classes to your MATLAB path.

classdef ClassA
    properties
        Property1 ClassB
        PropertySelf ClassA
    end
end
classdef ClassB
    properties
        Property1 double
    end
end

Open the Class Diagram Viewer. In the Class Browser pane, expand the Import Class, Namespace, or Folder button and select Import Class. Enter ClassA and click OK. Repeat this step for ClassB. Both classes appear in the Class Browser.

Class Browser with ClassA and ClassB added

Drag ClassA and ClassB from the Class Browser to the canvas. Expand the ClassA 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.

ClassA and ClassB cards visible on canvas, ClassA expanded

In the View section of the toolstrip, select the Associations check box. This action adds arrows to the diagram for any identifiable associations. In this case:

  • Property1 of ClassA is of type ClassB, so an arrow connects Property1 to the class card for ClassB.

  • PropertySelf of ClassA is of type ClassA, so an arrow connects that property back to the main card for ClassA.

ClassA with arrows pointing to itself and ClassB

The arrows can be toggled on and off using the Associations check box. The arrows also appear even if the class cards are collapsed.

The Class Diagram Viewer can only identify associations when properties are defined using class validation. When defined this way, the class of the property is shown on the class card. For more information, see Property Class Validation. Also, turning on associations only shows connections between classes that are currently in the diagram. For example, if ClassB was not in the diagram, the app would not automatically add it to show the association with Property1 of ClassA.

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

  • Namespaces, with namespace 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.

Tips

  • 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. If a class file is deleted or becomes unavailable to the app, the app indicates the class is out of sync, but the class card itself is not removed from the diagram.

Version History

Introduced in R2021a

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See Also