How can I calculate dependent properties and assign them to the object?

Question

J. Hu 2013-9-28

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https://ww2.mathworks.cn/matlabcentral/answers/88527-how-can-i-calculate-dependent-properties-and-assign-them-to-the-object

回答： Yvo Putter 2018-1-15

Given a property for an object, need to calculate some values and assign them to the properties of the same object. I use following code but it does not work, showing three error messages.

 classdef GCSSetup
    properties
        Preference
    end
    properties (Dependent)
        VDir
        NDir
        EDir
        EDirAzDeg
        iCol
    end
    methods
        function [] = GCSDefine(GCS)
            % GCSPreference = 'VZ_NY'; % Vertical-Z / North -Y
            switch GCS.Preference
                case 'VZ_NY'
                    GCS.VDir = 'ZDir'; % System coordinate frame for Vertical direction
                    GCS.NDir = 'YDir'; % System coordinate frame for North direction
                    GCS.EDir = 'XDir'; % System coordinate frame for East direction
                    GCS.EDirAzDeg = 90;% Azimuth angle for east direction
                    % XDirDeg = 90;  % Azimuth for the X-frame direction in global coordinate system
                case ''
            end
            % iCol is the index to
            if     strcmp(GCS.VDir,'ZDir')==1, GCS.iCol=3;
            elseif strcmp(GCS.VDir,'YDir')==1, GCS.iCol=2;
            elseif strcmp(GCS.VDir,'XDir')==1, GCS.iCol=1;
            else
            end
        end
    end
end

Please help. Thanks...

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Image Analyst 2013-9-28

How are you instantiating and calling this? Please attach your classdef file and the test script that you use to call it.

J. Hu 2013-9-29

编辑：Image Analyst 2013-9-29

在 MATLAB Online 中打开

I used following code to call the function:

GCSPreference = 'VZ_NY'; % Vertical-Z / North -Y
GCS = GCSSetup(GCSPreference);

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Answer 1

Matt J 2013-9-29

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https://ww2.mathworks.cn/matlabcentral/answers/88527-how-can-i-calculate-dependent-properties-and-assign-them-to-the-object#answer_98128

编辑：Matt J 2013-9-29

在 MATLAB Online 中打开

You cannot store actual data to a Dependent property as you try to do, for example, in

GCS.VDir = 'ZDir';

The whole point of a Dependent property is that it never actually stores data.

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J. Hu 2013-9-29

编辑：Matt J 2013-9-29

在 MATLAB Online 中打开

After I changed the name of the function to be the same as the class name like below, it works.

GCSPreference = 'VZ_NY'; % Vertical-Z / North -Y
GCS = GCSSetup(GCSPreference);
classdef GCSSetup
    properties
        Preference
    end
      properties (Dependent)
          VDir
          NDir
          EDir
          EDirAzDeg
          iCol
      end
      methods
          function Obj = GCSSetup(GCSPreference)
              % GCSPreference = 'VZ_NY'; % Vertical-Z / North -Y
              Obj.Preference = GCSPreference;
              switch Obj.Preference
                  case 'VZ_NY'
                      Obj.VDir = 'ZDir'; % System coordinate frame for Vertical direction
                      Obj.NDir = 'YDir'; % System coordinate frame for North direction
                      Obj.EDir = 'XDir'; % System coordinate frame for East direction
                      Obj.EDirAzDeg = 90;% Azimuth angle for east direction
                      % XDirDeg = 90;  % Azimuth for the X-frame direction in global coordinate system
                  case ''
              end
              % iCol is the index to
              if     strcmp(Obj.VDir,'ZDir')==1, Obj.iCol=3;
              elseif strcmp(Obj.VDir,'YDir')==1, Obj.iCol=2;
              elseif strcmp(Obj.VDir,'XDir')==1, Obj.iCol=1;
              else
              end
          end
      end
  end

Then I check GCS, it shows all the properties correctly. What is the difference? Did you use the properties correctly? Thanks...

Matt J 2013-9-30

编辑：Matt J 2013-9-30

I don't see what's strange. The only way to access Dependent properties is to define set() and get() methods that generate on-the-fly values for the property. You do not appear to have done that.

per isakson 2013-10-6

在 MATLAB Online 中打开

Here (R2013a, Win7) your code returns the following error

    In class 'GCSSetup', no set method is defined for Dependent property
    'VDir'.  A Dependent property needs a set method to assign its value.
    Error in GCSSetup (line 24)
       Obj.VDir = 'ZDir'; % System coordinate frame for Vertical direction