Simulink Code Generation Error: Array of Classes Initalization

Hello,

I am trying to built a Simulink function which keeps record of the statistics of the system by using array of classes. However, I can not generate an array of class in Simulink. I realize that I should instantiate an array in Simulink but how can I instantiate a class?

    arrivedArray(3, 65536) = queueInfo;
    analysisArray(3, 65536) = queueInfo;

In the picture above, queueInfo is my class. This two lines return with the following error.

Code generation requires variable arrivedArray to be fully defined before subscribing it.

By the way, this is the suggested method by Matlab for creating an array of class but somehow it doesn't work. Later I've tried this one:

        persistent arrivedArray
    if isempty(arrivedArray)
        arrivedArray(3, 655336) = queueInfo;
    end
    persistent analysisArray
    if isempty(analysisArray)
        analysisArray(3, 65536) = queueInfo;
    end
    

But it doesn't work either. The error İs:

Persistent variable 'arrivedArray' must be assigned before it is used. The only exception is a check using 'isempty(arrivedArray)' that can be performed prior to assignment.

I understand the error but have no idea how to fix it. A constructor did not help me too. Here is my class structure:

1

    classdef transactionInfo
    properties
        tag = uint16(0);
        arrivalTime = uint64(0);
        departureTime = uint64(0);
    end
    methods
        function obj = transactionInfo(v)
            if nargin > 0
                obj.tag = uint16(v);
                obj.arrivalTime = uint64(v);
                obj.departureTime = uint64(v);
            end
        end
    end
end

2

classdef queueInfo < transactionInfo
    properties
        length = uint16(0);
        queueID = uint8(0);
        delay = uint64(0);
    end
    methods
        function obj = queueInfo(v)
            if nargin > 0
                obj.length = uint16(v);
                obj.queueID = uint8(v);
                obj.delay = uint64(v);
            end
        end
    end
end

Does anyone know how to fix this issue?

Note: There might be some obvious errors in my class structures, I am kind of new to OOP. Every suggestion is welcomed.

Answer 1

[Harsh]

Hi @MU,

The errors you are receiving are because of the variables not being properly instantiated before using them. Please refer to the following documentation to understand more about this - https://www.mathworks.com/help/coder/ug/resolve-issue-elements-must-be-fully-defined-before-use.html

Also, in MATLAB code generation does not support object arrays so you must create cell array for your problem. Please refer to the following documentation to understand more about this problem - https://www.mathworks.com/help/coder/ug/resolve-error-code-generation-does-not-support-object-arrays.html

Below is an example code snippet to resolve your issue –

function res = testCellArray() 

    %#codegen 

    % Define the size of the cell array 

    numRows = 3; 

    numCols = 65536; 

     

    % Initialize the cell array 

    arrivedArray = cell(numRows, numCols); 

     

    % Populate the cell array with instances of queueInfo 

    for i = 1:numRows 

        for j = 1:numCols 

            arrivedArray{i, j} = queueInfo(); % Instantiate each element 

        end 

    end 

    res=arrivedArray{numRows,numCols}; 

end