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

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Mahshooq Majeed
Mahshooq Majeed on 21 Jun 2021
Edited: per isakson on 24 Jun 2021
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

Answers (1)

per isakson
per isakson on 24 Jun 2021
Edited: per isakson on 24 Jun 2021
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: {}

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