Class Metadata - MATLAB & Simulink (original) (raw)

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What Is Class Metadata?

Class metadata is information about class definitions that is available from various metaclasses objects. Use metaclass objects to obtain information without having to create instances of the class. Metadata enables the programmatic inspection of classes. Each metaclass has properties, methods, and events that contain information about the class or class component it describes.

All class components have an associated metaclass, which you access from thematlab.metadata.Class object. For example, create thematlab.metadata.Class object for thematlab.alias.AliasFileManager class:

mc = ?matlab.alias.AliasFileManager

mc =

Class with properties:

                 Name: 'matlab.alias.AliasFileManager'
          Description: 'Create and edit alias definition files'
  DetailedDescription: '  Use an AliasFileManager object to create...'
               Sealed: 1
             Abstract: 0
          Enumeration: 0
      ConstructOnLoad: 0
     HandleCompatible: 1
      InferiorClasses: [0×1 matlab.metadata.Class]
            Namespace: [1×1 matlab.metadata.Namespace]
              Aliases: [0×1 string]
 RestrictsSubclassing: 1
         PropertyList: [1×1 matlab.metadata.Property]
           MethodList: [28×1 matlab.metadata.Method]
            EventList: [1×1 matlab.metadata.Event]
EnumerationMemberList: [0×1 matlab.metadata.EnumerationMember]
       SuperclassList: [1×1 matlab.metadata.Class]

The `matlab.metadata` Namespace

The matlab.metadata namespace contains metaclasses that describe the definition of classes and class components. The class name indicates the component described by the metaclass. For example, each class property has amatlab.metadata.Property associated with it. Attributes defined for class components correspond to properties in the respective metaclass object.

matlab.metadata.Namespace — Access from matlab.metadata.Class Namespace property.
matlab.metadata.Class — Create from class name or class object using metaclass function or? operator.
matlab.metadata.Property — Access from matlab.metadata.Class PropertyList property.
matlab.metadata.DynamicProperty — Obtain from the addprop method.
matlab.metadata.Method — Access from matlab.metadata.Class MethodList property.
matlab.metadata.Event — Access from matlab.metadata.Class EventList property.
matlab.metadata.EnumerationMember — Access from matlab.metadata.Class EnumerationMemberListList property.

Metaclass Objects

You cannot instantiate metaclasses directly by calling the respective class constructor. Create metaclass objects from class instances or from the class name.

?_`ClassName`_ — Returns amatlab.metadata.Class object for the named class. Usematlab.metadata.Class.fromName with class names stored as characters in variables.
matlab.metadata.Class.fromName('_`ClassName`_') — returns the matlab.metadata.Class object for the named class (matlab.metadata.Class.fromName is amatlab.metadata.Class method).
metaclass(obj) — Returns a metaclass object for the class instance (metaclass)

Create matlab.metadata.Class object from class name using the? operator:

Create matlab.metadata.Class object from class name using thefromName method:

mc = matlab.metadata.Class.fromName('MyClass');

Create matlab.metadata.Class object from class instance

obj = MyClass; mc = metaclass(obj);

The metaclass function returns thematlab.metadata.Class object (that is, an object of thematlab.metadata.Class class). You can obtain other metaclass objects (matlab.metadata.Property,matlab.metadata.Method, and so on) from thematlab.metadata.Class object.

Note

Metaclass is a term used here to refer to all the classes in thematlab.metadata namespace.matlab.metadata.Class is a class in thematlab.metadata namespace whose instances contain information about MATLAB® classes. Metadata is information about classes contained in metaclasses.

Metaclass Object Lifecycle

When you change a class definition, MATLAB reloads the class definition. If instances of the class exist, MATLAB updates those objects according to the new definition.

However, MATLAB does not update existing metaclass objects to the new class definition. If you change a class definition while metaclass objects of that class exist, MATLAB deletes the metaclass objects and their handles become invalid. You must create a new metaclass object after updating the class.

For information on how to modify and reload classes, see Automatic Updates for Modified Classes.

Class Metadata - MATLAB & Simulink (original) (raw)

What Is Class Metadata?

The matlab.metadata Namespace

Metaclass Objects

Metaclass Object Lifecycle

Related Topics

The `matlab.metadata` Namespace