Model Complex Objects in Activity Diagrams Using MATLAB Class Tokens

This example shows how to model an activity diagram representation of a system that processes tokens containing complex objects. In activity diagrams, you can model complex objects, which contain specialized data structures or large number of functions using MATLAB class tokens. The class can either be a value class or a handle class. For information on this, see Comparison of Handle and Value Classes.

This example models a login authentication system using login credentials that are stored as MATLAB classes. The activity diagram has the following nodes:

• Enter Login Credentials action node, which accepts login credentials from the user.

• Validate Credentials action node, which verifies whether the entered pin is an even number with at least four digits.

• Decision node, which checks whether the login succeeded or not.

  • If the IsSuccess function returns a True value, the token flows towards the LoginSuccesful action node.

  • If the IsSuccess function returns a false value, the token flows towards Increment number of tries action node.

• Increment number of tries action node, which counts the number of failed login attempts.

For more information about activity diagrams, see Describe System Behavior Using Activity Diagrams.

Open Activity Diagram for Login Session

From the example file, open the activity diagram.

open("LoginActivity.slx")

Define LoginSession Class

Create a custom MATLAB class called LoginSession and define its associated properties and methods. To use a MATLAB class, it has to be on the file path.

The LoginSession class defines public properties such as the user name, date of birth, and pin number, along with private properties such as the number of login attempts and login status.

The class method defines the constructor that initializes login credentials and the functions that are necessary for the activity diagram to simulate a login session.

classdef LoginSession
    % Example MATLAB class that defines a login session object with
    % internal logic for validating credentials and allowing retries.
    
    properties
        UserName = ""
        DateOfBirth = datetime([0 0 0])        
        PinNumber = 0
    end

    properties (Access = private)
        NumTries = 0
        Success = false
    end

    properties (Constant)
        MaxTries = 3;
    end

    methods
        % Constructor
        function obj = LoginSession()
            % Create a LoginSession object with default property values
        end

        % Validate credentials
        function obj = ValidateCredentials(obj)        
            % Pin must an even number with at least 4 digits
            obj.Success = (obj.PinNumber > 999) && (mod(obj.PinNumber, 2) == 0);            
        end

        % Increase number of tries
        function obj = IncrementTries(obj)
            obj.NumTries = obj.NumTries + 1;
        end        

        % Whether login is successful
        function result = IsSuccess(obj)
            result = obj.Success;
        end        

        % Whether retry is allowed
        function result = IsRetryAllowed(obj)
            result = (obj.NumTries <= obj.MaxTries);
        end
    end
end

Note these considerations and limitations when you use MATLAB class tokens.

• Signal logging and breakpoints are not supported with flows that contain MATLAB class tokens.

• Port value labels are inaccessible for flows that use MATLAB class tokens.

• When you step back during a simulation, restoring tokens containing handle objects is not supported.

Configure Pins to Accept MATLAB Class Tokens

To enable MATLAB class tokens to flow through a pin, configure each pin to accept or generate a MATLAB class token.

In the activity diagram, open the Property Inspector and select the pin.

In the Name list, select owned. In the Type field, enter LoginSession.

For example, input pin of the Enter Login Credentials action node now expects a token with the MATLAB class LoginSession.

Create Conditional Flow with MATLAB Class Function

To access a function of the LoginSession class for the decision node, use the built-in keyword token followed by the method name.

In this example, when the IsRetryAllowed function of the class returns a True value, the token flows back to the Enter Login Credentials action node. Otherwise, the token is routed to the Display Error action node.