meta.class

Describe MATLAB class

Description

Instances of the meta.class class contain information about MATLAB^® classes. The read/write properties of the meta.class class correspond to class attributes and are set only from within class definitions on the classdef line. You can query the read–only properties of the meta.class object to obtain information that is specified syntactically by the class (for example, to obtain the name of the class).

You cannot instantiate a meta.class object directly. You can construct a meta.class object from an instance of a class or using the class name:

• metaclass — returns a meta.class object representing the object passed as an argument.

• ?ClassName — returns a meta.class object representing the named class.

• fromName — static method returns a meta.class object representing the named class.

For example, the metaclass function returns the meta.class object representing MyClass.

ob = MyClass;
obmeta = metaclass(ob);
obmeta.Name

ans =
MyClass

You can use the class name to obtain the meta.class object:

obmeta = ?MyClass;

You can also use the fromName static method:

obmeta = meta.class.fromName('MyClass');

Properties

Property	Purpose
Abstract attribute, default = false	If true, this class is an abstract class (cannot be instantiated). For more information, see Abstract Classes.
ConstructOnLoad attribute, default = false	If true, MATLAB calls the class constructor automatically when loading an object from a MAT-file. Therefore, the construction must be implemented so that calling it with no arguments does not produce an error. See Save and Load Process for Objects
ContainingPackage read only	A meta.package object describing the package within which this class is contained, or an empty object if this class is not in a package. See Packages Create Namespaces.
Description read only	Currently not used.
DetailedDescription read only	Currently not used.
Enumeration attribute, default = false	If true, this class is an enumeration class. See Define Enumeration Classes.
EventList read only	An array of meta.event objects describing each event defined by this class, including all inherited events. See Events.
EnumerationMemberList	An array of meta.EnumeratedValue objects describing the member names defined by an enumeration class. See Enumerations for more information on enumeration classes.
Hidden attribute, default = false	If set to true, the class does not appear in the output of MATLAB commands or tools that display class names.
InferiorClasses attribute, default = {}	A cell array of meta.class objects defining the precedence of classes represented by the list as inferior to this class. See Class Precedence
MethodList read only	An array of meta.method objects describing each method defined by this class, including all inherited public and protected methods. See Methods in Class Design.
Name read only	Name of the class associated with this meta.class object (char array)
PropertyList read only	An array of meta.property objects describing each property defined by this class, including all inherited public and protected properties. See Properties.
RestrictsSubclassing read only	If the class is not Sealed and has an empty list of AllowedSubclasses in the class definition, this property is set to false. If the class is Sealed or specifies any AllowedSubclasses, this property is set to true. See Specify Allowed Subclasses.
Sealed attribute, default = false	If true, the class cannot be subclassed.
SuperclassList read only	An array of meta.class objects describing each direct superclass from which this class is derived. See Design Subclass Constructors.

Methods

Method	Purpose
fromName	Returns the meta.class object associated with the specified class name.
tf = eq(Cls)	Equality function (a == b). Use to test if two variables refer to equal classes (classes that contain exactly the same list of elements).
tf = ne(Cls)	Not equal function (a ~= b). Use to test if two variables refer to different meta–classes.
tf = lt(ClsA,ClsB)	Less than function (ClsA < ClsB). Use to determine if ClsA is a strict subclass of ClsB (i.e., a strict subclass means ClsX < ClsX is false).
tf = le(ClsA,ClsB)	Less than or equal to function (ClsA <= ClsB). Use to determine if ClsA is a subclass of ClsB.
tf = gt(ClsA,ClsB)	Greater than function (ClsA > ClsB). Use to determine if ClsA is a strict superclass of ClsB (i.e., a strict superclass means ClsX > ClsX is false).
tf = ge(ClsA,ClsB)	Greater than or equal to function (ClsA >= ClsB). Use to determine if ClsA is a superclass of ClsB.

Events

Event	Purpose
InstanceCreated	If the class is a handle class, this event occurs every time a new instance of this handle class is created, including new instances of any subclasses. The event occurs immediately after all constructor functions finish executing.
InstanceDestroyed	If the class is a handle class, this event occurs every time an instance of this handle class is destroyed, including all subclasses. The event occurs immediately before any destructor functions execute.

Examples

Find property attributes using the handle class findobj method and the audioplayer meta.class object. Determine if you can change the SampleRate property on an audioplayer object.

load('handel.mat')
player = audioplayer(y,Fs);
mc = metaclass(player);
mp = findobj(mc.PropertyList,'Name','SampleRate');
if strcmp(mp.SetAccess,'public')
   player.SampleRate = 7200;
end