Help with findobj error: "Invalid parameter/value pair arguments"

Hi, I have a class called 'ChessGame,' whose code is as follows:

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(The code itself isn't too important and doesn't need to be read. It's just required to illustrate my problem with findobj)

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classdef ChessGame < handle
    %CHESSGAME A class for playing and replaying chess games
    %   Create an instance and use the PLAY() method to play manually,
    %   or use the static method REPLAY() to replay a previous game.
    %   See the help for each method (e.g., "help ChessGame.play")
    %   for details.

      properties (Access = private, Hidden = true)
          Board
          KingList = {}
          Playing = []
      end

      properties
          Directions = []
      end

      methods
          function game = ChessGame()
              game.Board = ChessBoard();
              game.initializeBoard();
          end

          function directions = play(game)
              %DIRECTIONS = PLAY(GAME) play() allows you play a chess game
              %manually
              %   If a new game is already in progress, PLAY will continue
              %   it.  Otherwise, it starts a new game.  Team 1 goes first.
              %   It will first display a numbered list of the pieces that 
              %   are available to move along with their current position.
              %   You can enter the piece number, or the position as a 1x2
              %   array (remember the square brackets!).  Once you have
              %   selected a piece, it will display the positions it can move
              %   to and the pieces it can capture.  Enter the position to
              %   move to in square brackets.
              %
              %   The game does not detect checks or checkmates.  Therefore,
              %   it is necessary to actually capture the king to win.  Once
              %   this happens, the game is over.
              %
              %   At any prompt, you can enter -1 to exit the game.  The
              %   state of the game is saved.  The method returns an array of
              %   moves that can be used with the replay method.
              if isempty(game.Playing) || game.Playing == 0
                  if game.Playing == 0
                      disp('Game has ended. Resetting board.');
                  end
                  game.Directions = [];
                  game.Board = ChessBoard();
                  game.initializeBoard();
                  game.Playing = 1;
              end
              bd = game.Board;
              display(bd);
              while game.Playing ~= 0
                  team = game.Playing;
                  disp('');
                  disp(['Team ' num2str(team) '''s turn']);
                  disp('Pick a piece to move');
                  pieces = {};
                  for y = 1:8
                      for x = 1:8
                          [occ pc] = bd.checkPosition([x y]);
                          if occ && pc.Team == team
                              pieces{end+1} = pc;
                          end
                      end
                  end
                  for i = 1:length(pieces)
                      piece = pieces{i};
                      if ~isempty(piece.getMoves())
                          disp([num2str(i,'%02u') ': ' piece.getSymbol()...
                              ' at ' num2str(piece.Position(1))...
                              ',' num2str(piece.Position(2))]);
                      end
                  end
                  in = input('Enter piece number or position (in square brackets): ');
                  if in == -1
                      directions = game.Directions;
                      return;
                  end
                  if length(in) == 2
                      [~,pc] = game.Board.checkPosition(in);
                      if ~isempty(pc) && pc.Team == team
                          selected = pc;
                      else
                          error('Invalid position');
                      end
                  else
                      selected = pieces{in};
                  end
                  allMoves = selected.getMoves();
                  moves = [];
                  kills = [];
                  for i = 1:size(allMoves)
                      move = allMoves(i,:);
                      if move(3) == 0
                          moves(end+1,:) = move(1:2);
                      else
                          kills(end+1,:) = move(1:2);
                      end
                  end
                  disp('Moves:');
                  for i = 1:size(moves,1)
                      disp([num2str(moves(i,1))...
                              ',' num2str(moves(i,2))]);
                  end
                  disp('Attack moves:');
                  for i = 1:size(kills,1)
                      [~,piece] = game.Board.checkPosition(kills(i,:));
                      disp([piece.getSymbol()...
                              ' at ' num2str(piece.Position(1))...
                              ',' num2str(piece.Position(2))]);
                  end
                  move = input('Enter move (in square brackets): ');
                  if move == -1
                      directions = game.Directions;
                      return;
                  end
                  game.Directions(end+1,:) = [selected.Position move];
                  selected.move(move);
                  display(game.Board);
                  game.Playing = mod(game.Playing,length(game.KingList))+1;
              end
              directions = game.Directions;
          end

          function display(game)
              if isempty(game.Playing) || game.Playing == 0
                  disp('This game is not currently active');
              else
                  disp(['Team ' num2str(game.Playing) ' is playing next']);
              end
              if ~isempty(game.Directions)
                  disp([num2str(size(game.Directions,1))...
                      ' moves have been made already']);
              end
          end

      end

      methods(Hidden = true)

          function addKing(game,king)
              if king.Team <= length(game.KingList) ...
                      && ~isempty(game.KingList{king.Team})
                  error('That team already has a king!');
              else
                  game.KingList{king.Team} = king;
              end
          end

          function checkmate(game,king)
              disp(['Game over! Team ' num2str(king.Team) ' loses!']);
              game.Playing = 0;
          end

      end
      methods (Access = private, Hidden = true)
          function initializeBoard(game)
              bd = game.Board;
              game.KingList = {};
              Rook([1 1],bd,1);
              Knight([2 1],bd,1);
              Bishop([3 1],bd,1);
              Queen([4 1],bd,1);
              King([5 1],bd,1,game);
              Bishop([6 1],bd,1);
              Knight([7 1],bd,1);
              Rook([8 1],bd,1);
              for i = 1:8
                  Pawn([i 2],bd,1);
              end
              Rook([1 8],bd,2);
              Knight([2 8],bd,2);
              Bishop([3 8],bd,2);
              Queen([4 8],bd,2);
              King([5 8],bd,2,game);
              Bishop([6 8],bd,2);
              Knight([7 8],bd,2);
              Rook([8 8],bd,2);
              for i = 1:8
                  Pawn([i 7],bd,2);
              end
          end

      end

      methods (Static)
          function replay(directions)
              %REPLAY(DIRECTIONS) Replays a saved chess game.
              %   This is a static method, so it is called using 
              %   ChessGame.replay(directions).  You don't need to create an
              %   instance of the game to play it.  You can use as input a 4
              %   column array of from-position to-position moves.  They must
              %   be valid, or you will get errors.  You can use the output
              %   of the PLAY() method, or either of the arrays in games.mat.
              game = ChessGame();
              game.Board = ChessBoard();
              game.initializeBoard();
              bd = game.Board;
              display(bd);
              pause(.5);
              for i = 1:size(directions,1)
                  move = directions(i,:);
                  [~, pc] = bd.checkPosition(move(1:2));
  %                 keyboard
                  pc.move(move(3:4));
                  display(bd);
                  pause(.5);
              end
          end
      end
  end

I want to extract all the properties (including private and hidden ones) so properties('ChessGame') does not suffice. I've been trying to use meta classes to do this but it keeps on throwing an error

??? Error using ==> findobjinternal
Invalid parameter/value pair arguments.

The code I'm trying to use is as follows:

clc
clear all

mc = ?ChessGame;

A = {findobj(mc.Properties,'GetAccess','private')}

The output should theoretically be 'Board' 'KingList' and 'Playing.'

Any and all help would be greatly appreciated. Sorry for the long post!

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The answer below solved the first problem... Thank you!

However, i'm faced with one last hurdle:

I'm trying to use the format below

H = FINDOBJ(ObjectHandles, 'flat', 'P1Name', P1Value,...) restricts the search only to the objects listed in ObjectHandles. Their descendents are not searched.

because I don't want any of the parents or descendents to be mixed in. however, when i run

{findobj([mc.Properties{:}], 'flat', 'GetAccess', 'private')}

it returns:

??? Error using ==> findobj Incomplete parameter-value pair.

What am I doing wrong?

Answer 1

[Walter Roberson]

At least in the version I am using, findobj() does not accept a cell array for the list of handles. Try

{findobj([mc.Properties{:}], 'GetAccess', 'Private')}

[Matt Tearle]

D'oh, too slow again!

Pum Sang, the error message is cryptic -- the real problem is that the output from mc.Properties is a cell array. Walter's solution converts it to an array of meta.Properties.

[Pum Sang]

woooow... thanks so much ^^;; I feel dumb now for not seeing that. lol. I do however have one question:

I'm trying to use the format below

H = FINDOBJ(ObjectHandles, 'flat', 'P1Name', P1Value,...)

restricts the search only to the objects listed in

ObjectHandles. Their descendents are not searched.

because I don't want any of the parents or descendents to be mixed in. however, when i run

{findobj([mc.Properties{:}], 'flat', 'GetAccess', 'private')}

it returns:

??? Error using ==> findobj

Incomplete parameter-value pair.

Sorry for asking so many questions... I've never used this function before and it is driving me crazy.

[Matt Tearle]

No worries, it's non-trivial! I'm not really sure why you can't use the 'flat' property. I'm guessing that it's something to do with the difference between findobj and handles.findobj, but... that's as much as I can work out right now. Anyway, will this do what you want?

{findobj([mc.Properties{:}], '-depth',1, 'GetAccess', 'private')}