Warnings on set-methods in a class?

I'm a retired developer and now and have started Arduino programming and have some habits from OOP in my younger days.

I used NOT DIRECTLY to manipulate the properties of class but do it by use of get/set-methods.

When I do that here I get WARNINGS - look here:

warning: ISO C++ forbids declaration of 'setState' with no type [-fpermissive]

Here is my code for the setState-method:

LED_Controller::setState(int st) {
_state = st;
}

and here is the most of my header file:

class LED_Controller {
private:
byte _pin = 0;
int _state = 0;
unsigned long _lastChanged = 0;
unsigned long _timeToActivate = 0;

public:

LED_Controller(byte GPIO_pin, 
               int state, 
               unsigned long lastChng,
               unsigned long timeToActi);
unsigned int  getTimeToActivate();
unsigned int  getLastChanged();
              setLastChanged(unsigned int lc);
int           getState();
              setState(int st);           <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< Here is the method !
byte          getPin();
unsigned long toggleLED();

};

I have 2 questions to ask you PROs:

  1. What is "best practice" - to manipulate the properties DIRECTLY or by set/get-methods ?
  2. How do I get rid of these warnings ?

Use "void"

Always use setters/getters

Please remember to use code tags when posting code

You must always tell the compiler the type of the return value of your function. If it doesn't have a return value you must use the type 'void'.

              void setState(int st);           <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< Here is the method !

Arghhhh, ofcause the void should be there
AND
I'll de the formatting in the future

THX for the quick responce to en newbee fool !'