Split a C++ class declaration

Question

I want to know if I can split a C++ class declaration

Original class

    class P
    {
        private: 
           int id;
           //some really          


        

Answer 1

Something like this?

class P
{
private:
    class Impl
    {
    public:
       int id;
       //some really secret method
       int secretMethod();
    };

private:
    Impl* _pimpl;

protected:
    int x;

public:
    P() : _pimpl(new P::Impl()) {}
    ~P() { delete _pimpl; } 
    int getX();

};