MATLAB: Class Undefined Function or Variable

Question

in the class shown .. I got the errors as below:

1.

"Invalid default value for property 'VarSize' in class 'particle':
Undefined function or variable 'nVar'."

2.

 "particle Undefined function or variable 'VarMin'.
  Error in particle (line 45)
            obj.position = unifrnd(VarMin, VarMax, VarSize); "

3.

   "particle
  Undefined function or variable 'CostFunction'.
  Error in particle (line 51)
              obj.cost = CostFunction(obj.position); "

code is:

classdef particle
    %PARTICLES Summary of this class goes here
    %   Detailed explanation goes here
      properties
          CostFunction = @(x) Sphere(x);              % Cost Function
          nVar = 2;               % Number of Unknown (Decision) Variables
          VarSize = nVar;        % Matrix Size of Decision Variables
          VarMin = -10;           % Lower Bound of Decision Variables
          VarMax =  10;           % Upper Bound of Decision Variables
          MaxIt = 100;            % Maximum Number of Iterations
          nPop = 50;              % Population Size (Swarm Size)
          w = 1;                  % Inertia Coefficient
          c1 = 2;                 % Personal Acceleration Coefficient
          c2 = 2;                 % Social (Global) Acceleration Coefficient
          position = [];
          velocity = [];
          cost = [];
          bestPosition = [];
          bestCost = [];
      end
      methods
          function z = sphere(x)
              z = sum(x.^2);
          end
          function [ obj ] = particle( varargin )
              % Generate Random Solution
              obj.position = unifrnd(VarMin, VarMax, VarSize);
              % Initialize Velocity
              obj.velocity = zeros([1 2]);
              % Evaluation
              obj.cost = CostFunction(obj.position);
              % Update the Personal Best
              obj.bestPosition = obj.position;
              obj.bestCost = obj.cost;
          end
      end
end

Answer 1

You need to change

              obj.position = unifrnd(VarMin, VarMax, VarSize);

to

                obj.position = unifrnd(obj.VarMin, obj.VarMax, obj.VarSize);