PSO (particle swarm optimization) Error Coding

I've coded a PSO as below:

classdef particle
    %PARTICLES Summary of this class goes here
    %   Detailed explanation goes here

      properties

          % Parameters
          VarMin = -10;
          VarMax = 10;
          VarSize = 2;

          % Template
          position = [];
          velocity = [];
          cost = [];
          bestPosition = [];
          bestCost = [];

          % Initialize Global Best
          GlobalBest = inf;

      end

      methods

          function [ obj ] = particle( varargin )

              function circle = CostFunction(x,y)

                  circle = (x.^2)+(y.^2);

              end

              % Generate Random Solution
              obj.position = unifrnd(obj.VarMin, obj.VarMax, obj.VarSize);

              % Initialize Velocity
              obj.velocity = zeros(obj.VarSize);

              % Evaluation
              obj.cost = CostFunction(obj.position,obj.position);

              % Update the Personal Best
              obj.bestPosition = obj.position;
              obj.bestCost = obj.cost;

              % Update Global Best   
              if obj.bestCost < obj.GlobalBest.Cost
                  obj.GlobalBest = obj.GlobalBest.best;
              end

          end
      end

end

and have an error:

Struct contents reference from a non-struct array object.
Error in particle (line 51)
            if obj.bestCost < obj.GlobalBest.Cost

Answer 1

[Walter Roberson]

You have

GlobalBest = inf;

so GlobalBest is numeric, not a struct.

[Ali Ali]

Okay.. and what should I do?

[Ali Ali]

I've removed (.cost) from (GlobalBest) and it works, so, if that what you mean.. thank you.

[Walter Roberson]

What you needed to do was be consistent in the data type of the variables. You solved it one way, and another way would have been to initialize to a struct instead of to numeric.

[Ali Ali]

Okay, what is your recommendation?

[Walter Roberson]

I am not sure that you need to make any more changes.

[Ali Ali]

I appreciate this.