When constructing an instance of class, the constructor must preserve the class of the returned object.

I'm currently working on a project, I've never worked with OOD in Matlab before and it seems really overwhelming. When compiling the code with main file it gives error statating "When constructing an instance of class 'cSubstance', the constructor must preserve the class of the returned object."

classdef cSubstance
    properties
        varargin
    end
    methods
        function this = cSubstance(varargin)
                this = struct( ...
                        'mName', [],...         %Name 
                        'mMW', [],...            %Molecular weight (g/mol)
                        'mTc', [],...            %Critical temperature (K)
                        'mPc', [],...            %Critical pressure (Pa)
                        'mw', [],...             %Acentric factor
                        'mAntA', [],...          %Parameter A of Antoine equation, lnP(Pa) = A-B/(T(K)+C)
                        'mAntB', [],...          %Parameter B of Antoine equation, lnP(Pa) = A-B/(T(K)+C)
                        'mAntC', [],...          %Parameter C of Antoine equation, lnP(Pa) = A-B/(T(K)+C)
                        'mTf', [],...            %Melting temperature at the triple point (K)
                        'mHf', [],...            %Melting enthalpy at the triple point (J/mol)
                        'mEoSParam', []);        %EoS-specific parameter(s)
                
                %Initialize parameters
                this.mName = ' ';
                this.mMW = 0;
                this.mTc = 0;
                this.mPc = 0;
                this.mw = 0;
                this.mAntA = 0;
                this.mAntB = 0;
                this.mAntC = 0;
                this.mTf = 0;
                this.mHf = 0;
                this.mEoSParam = {};
                
                if nargin > 0, this.mName = varargin{1}; end
                if nargin > 1, this.mMW = varargin{2}; end
                if nargin > 2, this.mTc = varargin{3}; end
                if nargin > 3, this.mPc = varargin{4}; end
                if nargin > 4, this.mw = varargin{4}; end
                if nargin > 5, this.mAntA = varargin{5}; end
                if nargin > 6, this.mAntB = varargin{6}; end
                if nargin > 7, this.mAntC = varargin{7}; end
                if nargin > 8, this.mTf = varargin{8}; end
                if nargin > 9, this.mHf = varargin{9}; end
                if nargin > 10, this.mEoSParam = varargin{10}; end
        end
    end
end

Answer 1

[per isakson]

I don't know C++. (For some reason you added the tag "C++".) I guess you are biased by some other language. You need to look closer at some Matlab documentation on OO.

I modified your class definition (see attached). Now creating an instance works.

cs = cSubstance('test') 

cs = 
  cSubstance with properties:

        mName: 'test'
          mMW: 0
          mTc: 0
          mPc: 0
           mw: 0
        mAntA: 0
        mAntB: 0
        mAntC: 0
          mTf: 0
          mHf: 0
    mEoSParam: {}