codereview.stackexchange.com - if you want a code review. Otherwise, the question about "the right way of 2 object accessing each other methods" is too broad. Also your case seems very simple, so my opinion would be: Motor (with e.g.
setSpeed(double)
method), Display (e.g. with
display(std::string)
method), and Controller (get user input, make a decision, update peripherals, return output) should do the job. —
pptaszni 34 secs ago