Using a private method to set a number of private properties

Question

Michael Dzjaparidze 2011-11-28

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https://ww2.mathworks.cn/matlabcentral/answers/22466-using-a-private-method-to-set-a-number-of-private-properties

I'm trying to work with OOP concepts in MATLAB but run into the following problem: I have a number of coefficients which need to be computed, based on some public properties inside a private class method. However, these properties are not set for some reason I don't quite understand. The method I have defined as:

methods (Access = private)
      function obj = calcSchemeCoefficients (obj)
          obj.lambda2 = (obj.gamma2*obj.k^2)/obj.h^2;
          obj.mu = (obj.kappa*obj.k)/obj.h^2;
          obj.mu2 = obj.mu^2;
          obj.zeta = (4*obj.b2*obj.mu)/obj.kappa;
          obj.den = 1+obj.b1*obj.k;
          obj.a10 = (2-2*obj.lambda2-6*obj.mu2-obj.zeta)/obj.den;
          obj.a11 = (obj.lambda2+4*obj.mu2+0.5*obj.zeta)/obj.den;
          obj.a12 = -obj.mu2/obj.den;
          obj.a20 = (-1+obj.zeta+obj.b1*obj.k)/obj.den;
          obj.a21 = (-0.5*obj.zeta)/obj.den;
          % this prints the correct result
          fprintf('\nlambda2: %f\n', obj.lambda2);
      end
  end

However when I try to recall the property lambda2 for use in another (public) function, it doesn't seem to contain any value... I suspect I am missing some logic here, but I really have no clue what it could be.

Any help on this would be greatly appreciated

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Answer 1

Daniel Shub 2011-11-28

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My guess is you are not handling the returned object correctly. Are you using a value class or a handle class? What happens when you do:

obja.lambda2
objb = calcSchemeCoefficients(obja)
objb.lambda2
obja.lambda2

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Michael Dzjaparidze 2011-11-28

You are right. I did not realize I had to assign the 'output' of calcSchemeCoefficients to obj again. so: obj = obj.calcSchemeCoefficients(); does the job actually. Thanks!

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