Documentation

Class Definitions on the Path

To call a class method, the class definition must be on the MATLAB^® path, as described in the next sections.

Class and Path Folders

There are two types of folders that can contain class definition files.

See the path function for information about the MATLAB path.

Using Path Folders

The class definition files in the folders are on the MATLAB path. Therefore, class definitions placed in path folders behave like any ordinary function with respect to precedence—the first occurrence of a name on the MATLAB path takes precedence over all subsequent occurrences of the same name.

The name of each class definition file must match the name of the class that is specified with the classdef keyword. Using a path folder eliminates the need to create a separate class folder for each class. However, the entire class definition, including all methods, must be contained within a single file.

Suppose that you have three classes defined in a single folder:

.../path_folder/MyClass1.m
.../path_folder/MyClass2.m
.../path_folder/MyClass3.m

To use these classes, add path_folder to your MATLAB path:

addpath path_folder

Using Class Folders

A class folder name always begins with the @ character followed by the class name for the folder name. A class folder must be contained in a path folder, but the class folder is not on the MATLAB path. Place the class definition file inside the class folder, which also can contain separate method files. The class definition file must have the same name as the class folder (without the @ character). The class definition (beginning with the classdef keyword) must appear in the file before any other code (white space and comments do not constitute code).

.../parent_folder/@MyClass/MyClass.m
.../parent_folder/@MyClass/myMethod1.m
.../parent_folder/@MyClass/myMethod2.m

Define only one class per folder. All files have a .m extension or, for MATLAB versions R2018a and later, standalone methods can be live functions with a .mlx extension.

Use a class folder when you want to use more than one file for your class definition. MATLAB treats any function file in the class folder as a method of the class. Function files can be MATLAB code (.m), Live Code file format (.mlx), MEX functions (platform dependent extensions), and P-code files (.p).

Class files provide the advantage that MATLAB can explicitly identify any file in the folder as a method of that class. For more information, see Changing Path to Update Class Definition.

The base name of each file must be a valid MATLAB function name. Valid function names begin with an alphabetic character and can contain letters, numbers, or underscores. For more information, see Methods in Separate Files.

Functions in Private Folders Within Class Folders

Private folders contain functions that are accessible only from functions defined in folders immediately above the private folder. Any functions defined in a private folder inside a class folder become methods of the class that have private access.

If a class folder contains a private folder, only the class defined in that folder can access functions defined in the private folder. Subclasses do not have access to superclass private functions. For more information on private folders, see Private Functions.

If you want a subclass to have access to the private functions of the superclass, define the functions as protected methods of the superclass. Specify the methods with the Access attribute set to protected.

Class Precedence and MATLAB Path

When there are multiple class definition files with the same name, the file location on the MATLAB path determines the file precedence. All class definition files before a class on the path take precedence, whether or not the definitions are contained in a class folder. The class takes precedence over all class definition files occurring later on the path.

For example, consider a path with the following folders, containing the files indicated.

Here is the logic that MATLAB applies to determine which version of Foo to call:

Class fldr1/Foo.m takes precedence over the class fldr3/@Foo because:

Class fldr3/@Foo takes precedence over function fldr2/Foo.m because:

Function fldr2/Foo.m takes precedence over class fldr5/Foo.m because:

Class fldr3/@Foo takes precedence over class fldr4/@Foo because:

If fldr3/@Foo/Foo.m does not contain a classdef keyword (that is, it is a MATLAB class created before Version 7.6), then fldr4/@Foo/bar.m becomes a method of the Foo class defined in fldr3/@Foo

Changing Path to Update Class Definition

Changing your MATLAB path can change the class definition file for a class (see path). However, for classes that are defined in path folders (that is, not in class @ folders), you must clear the class before MATLAB recognizes the new folder as the current class definition.

fldA/+FooPkg/@Foo/Foo.m
fldB/+FooPkg/@Foo/Foo.m

addpath fldA

a = FooPkg.Foo;

cd fldB

b = FooPkg.Foo;

fldA/+FooPkg/Foo.m
fldB/+FooPkg/Foo.m

addpath fldA

a = FooPkg.Foo;

cd fldB

clear FooPkg.Foo