Is it possible to temporarily disable the private attribute of object properties in debug mode in MATLAB 7.9 (R2009b)?

When I'm stepping through my code, it would be nice to be able to "peek" into the contents of private properties in my objects from scopes where this would not normally be possible during regular program execution. Is there a way to do this without having to set all of my properties to public temporarily and then setting them back to private when I'm done debugging?

For example, if I create the class definition:

classdef test
    properties(SetAccess= private, GetAccess=private)
        a = 'a'; 
        b='b'; 
    end
    properties
        c='c'; 
        d='d';
    end
end

and instantiate this object in another function, 'call_test.m':

function call_test
t = test;
end

I would like to be able to see the private properties of this object when running 'call_test.m' in debug mode.

Answer 1

[MathWorks Support Team]

The ability to temporarily disable the private attribute of object properties does not currently exist in MATLAB 7.9 (R2009b). You can access the private properties of objects while debugging using either of the following methods:

1. Temporarily set the GetAccess attribute of the properties to public

2. Create a public method to display the contents of the private properties, as in the following class definition. This method can use Meta-Classes to analyze the class definition and determine all property names.

classdef test
    properties(SetAccess= private, GetAccess=private)
        a = 'a'; 
        b='b'; 
    end
    properties
        c='c'; 
        d='d';
    end

      methods
          function mydisp(obj)    
             % To display the private data
             m = metaclass(obj);

             metaProps = m.Properties;

             nProps = numel(metaProps);
             disp('Properties:')
             for n=1:nProps           
                 fprintf(' %s:  %d (SetAccess = %s; Get Access = %s)\n',...
                     metaProps{n}.Name,metaProps{n}.DefaultValue,...
                     metaProps{n}.SetAccess, metaProps{n}.GetAccess)

             end        

          end
      end
  end

[per isakson]

"temporarily disable the private attribute of object properties" would invite the developer to access private properties in tests, which is disputable. This applies even more to private methods.

However, I think that in debug mode ("K>>") the private attribute should neither stop interactive access to properties nor to methods.

Answer 2

[per isakson]

The answer by the Team does not include the current values of the private properties. I modified their class to display the current values.

    >> dpp = display_private_property_demo;
    >> dpp = dpp.setPrivate( 'a', 'new_a' );
    >> dpp = dpp.setPrivate( 'b', 'mod_b' );
    >> dpp.mydisp
    Name        Default     Current     SetAccess   GetAccess   
    a           a           new_a       private     private     
    b           b           mod_b       private     private     
    c           c           c           public      public      
    d           d           d           public      public      
    >>

where

    classdef   display_private_property_demo
        properties   ( SetAccess = private, GetAccess = private )
            a = 'a';
            b = 'b';
        end
        properties
            c = 'c';
            d = 'd';
        end
        methods
            function mydisp( this )
                % To display the private data
                m = metaclass( this );

                metaProps = m.Properties;

                nProps = numel(metaProps);
                fprintf( '%-12s%-12s%-12s%-12s%-12s\n'               ...     
                ,   'Name','Default','Current','SetAccess','GetAccess' )
                for jj = 1 : nProps
                    fprintf( '%-12s%-12s%-12s%-12s%-12s\n'  ...        
                        ,   metaProps{jj}.Name           ...
                        ,   metaProps{jj}.DefaultValue   ...
                        ,   this.( metaProps{jj}.Name )  ...  <<<<<<
                        ,   metaProps{jj}.SetAccess      ...
                        ,   metaProps{jj}.GetAccess      ...
                        )
                end
            end
            function    this = setPrivate( this, name, value )
                this.( name ) = value;
            end
        end
    end