How to use the population in the fitness function in GA

Hi,

I am writing a code for Multiobjective GA in which I need the evolved population in each iteration as an input for fitness fuction . The following is the code:

FitnessFunction = @Mobject;
numberOfVariables = 100;
opts = optimoptions('gamultiobj','PopulationType','bitString'); 
[sub,fval,output] = gamultiobj(FitnessFunction,numberOfVariables,[],[],[],[],[],[],opts);

And the fitness function is:

function f = Mobject(sub,pop)
do
.
.
.
.
end

As you can see the population has to be an input for calculating the fitness of each individual but I do not know how to do it. I tried to use output function but it apparenlty give the results when the solver has done the job.

Has anyone got any idea?

Thanks