Audio Toolbox : Illegal use of reserved keyword "classdef"

% Ping Ping Delay Audio Plugin Class
% 
% Author: Nathanael Channings
% 
% Date: 14/11/20

classdef PingPongDelayPlugin < audioPlugin
    
    % Declare user Controlled Parameters
    
    properties
        
        % Output User Variables
        
        Wet = 0.7;
        Dry = 0.5;
        
        GainL = 0.8;
        GainR = 0.8;
        
        % Delay User Variables
        
        delayType = 2;      % 1(Straight)
                            % 2(pingPong)
        leftDelay = 0.3;    % Delay Value of the Right Channel
        rightDelay = 0.5;   % Delay Value of the Right Channel
        
        feedback = 0.7;     % Feedback Value for Both Channels
        
        % Distortion User Variable
        
        % Modulation User Variables
        
        % Reverb User Variables
        
        
    end
    
    % Declare Private Plugin Parameters
    
    properties (Access = private)
        
        % Delay Variables
        
        sDelayL = round(leftDelay*getSampleRate(plugin));
        sDelayR = round(rightDelay*getSampleRate(plugin));
        
        delayLineLeft = zeros(sDelayL,1);
        delayLineRight = zeros(sDelayR,1);
        
        dIdxL = 1;
        dIdxR = 1;
        
        % Filter Variables
        
        % Distortion Variables
        
        % Modulation Variables
        
        
        
        
    end
    
    % Design Plugin GUI
    
    properties (Constant)
        
        PluginInterface = audioPluginInterface(...
            audioPluginParameter('delayType','DisplayName','Delay Type','Style','rotaryknob','Mapping',{'int',1,3}),...
            audioPluginParameter('leftDelay','DisplayName','Left Delay','Style','rotaryKnob','Mapping',{'lin',0,2}),...
            audioPluginParameter('rightDelay','DisplayName','Right Delay','Style','rotaryKnob','Mapping',{'lin',0,2})...
            );
        
    end
    
    % This is Where Your DSP Lives
    
    methods
        
        function out = process(plugin,in)
            
            % Define the I/O Buffer Length
            
            L = max(size(in));
            
            out = zeros(L,2);   % Output Array
            d = zeros(N,2);     % Distortion Array
            m = zeros(N,2);     % Modulated Array
            
            % Create a Main Time Loop with the length of the buffer
            
            for n = 1:L
                
                % Define the Output
                
                out(n,1) = plugin.Dry*in(n,1) + plugin.Wet*plugin.delayLineLeft(plugin.dIdxL);
                out(n,2) = plugin.Dry*in(n,2) + plugin.Wet*plugin.delayLineRight(plugin.dIdxR);
                
                % Write Samples to the Delay Lines
                
                if plugin.delayType == 1
                    
                    tempL = plugin.feedback*plugin.delayLineLeft(plugin.dIdxL);
                    tempR = plugin.feedback*plugin.delayLineRight(plugin.dIdxR);
                    
                    plugin.delayLineLeft(plugin.dIdxL) = tempL;
                    plugin.delayLineRight(plugin.dIdxR) = tempR;
                    
                else if plugin.delayType == 2
                        
                        tempL = plugin.feedback*plugin.delayLineLeft(plugin.dIdxL);
                        tempR = plugin.feedback*plugin.delayLineRight(plugin.dIdxR);
                        
                        plugin.delayLineLeft(plugin.dIdxL) = tempR;
                        plugin.delayLineRight(plugin.dIdxR) = tempL;
                        
                    end
                    
                end
                
                % Iterate Through Each Delay Line Index
                
                plugin.dIdxL = plugin.dIdxL + 1;
                if plugin.dIdxL > plugin.sDelayL
                    plugin.dIdxL = 1;
                end
                plugin.dIdxR = plugin.dIdxR + 1;
                if plugin.dIdxR > plugin.sDelayR
                    plugin.dIdxR = 1;
                end
                
            end % End of for Loop
            
        end % End of Function
        
    end % End of Methods
    
end % End of Class

[Steven Lord]

Can you show us exactly how you're trying to use this class and the full and exact text of the error message you receive (everything displayed in red, and if there's any text displayed in orange include that too) when you try to use it?

[Nathanael Channings]

Hi Steven,

The Message received is as follows...

"Error: Illegal use of reserved keyword "classdef"."

When I try to validate the audio plugin I receive two additional errors...

"Invalid default value for property 'sDelayL' in class 'PingPongDelayPlugin':"

and

"Unrecognized function or variable 'leftDelay'."

Though I suspect the final two are unnrelated.

[Walter Roberson]

What action are you taking that triggers the classdef message?

[Nathanael Channings]

Running the script causes the classdef error message

Answer 1

[Steven Lord]

To use a class file you don't run the classdef file directly. You construct the object by calling the constructor (the function with the same name as the file) with the appropriate inputs. Because this classdef file does not contain an explicit constructor function, you'd call the default constructor that accepts no inputs.

myobj = PingPongDelayPlugin

Now you can call various functions on myobj.

[Nathanael Channings]

That command gives the result

myobj = 

  PingPongDelayPlugin with properties:

           Wet: 0.7000
           Dry: 0.5000
         GainL: 0.8000
         GainR: 0.8000
     delayType: 2
     leftDelay: 0.3000
    rightDelay: 0.5000
      feedback: 0.7000
      

However I'm still left with the two latter errors

Invalid default value for property 'sDelayL' in class 'PingPongDelayPlugin':

Unrecognized function or variable 'leftDelay'.

Answer 2

[Walter Roberson]

If you define a constant property then when you use the property to initialize other properties you must qualify with the class name.

https://www.mathworks.com/help/matlab/matlab_oop/expressions-in-class-definitions.html

Properties not declared as Constant or enumeration are considered variables and cannot be referenced directly in constructing default values. Instead you need to define a method that will be executed when the object is constructed. constants and enumerations are assigned when the class is constructed.

Remember that when you do not declare leftDelay constant then you are declaring that the user can change the value, and when you do that then which of the values should be used to construct new objects?

It is valid to construct a constant property to initialize with, and also to declare a variable property as the current value for any given object.

https://www.mathworks.com/help/matlab/matlab_oop/specifying-properties.html#brqy3km-10