Using attachInterrupt in library with non-static class member

Hello guys I found this:

class Foo{
  public:
    void bar();
};

Foo foo;

void setup(){
  attachInterrupt(0,fooBar,RISING);
}

void loop(){}

void fooBar(){
  foo.bar();
}

there: How to use attachInterrupt with a class member - Syntax & Programs - Arduino Forum

As minimum Sample, but this did not work, undefined reference to `Foo::bar()'

Is there an solution for this problem, to call an class member from attachInterrupt?

Markus_L811:
Is there an solution for this problem, to call an class member from attachInterrupt?

Your code is incomplete - it does not provide an implementation for the method void Foo::bar().

To fix the problem, provide an implementation.

PeterH:

Markus_L811:
Is there an solution for this problem, to call an class member from attachInterrupt?

Your code is incomplete - it does not provide an implementation for the method void Foo::bar().

To fix the problem, provide an implementation.

How?

My example looks like this:

.ino

#include .h

todo todo(10);

void setup() {
  // put your setup code here, to run once:

}

void loop() {
  // put your main code here, to run repeatedly: 
  
}

.h

void first(void);

class todo {
  public:
    todo (uint8_t pin);
    static void second();
    void third();  //could be bool or int as well with some parameter or only an flying step to go ahead
}

.cpp

todo::todo(uint8_t){
  attachInterrupt(pin, first, CHANGE);
}

void first(void) {
  todo::second();
}

void todo::second() {
  question how to call the non static function, calling from second not needed but there is I stuck
}

Markus_L811:
How?

Write the code for that method and put it in your source file, or another file within your project.

PeterH:

Markus_L811:
How?

Write the code for that method and put it in your source file, or another file within your project.

Please enlight me.

Markus_L811:
Please enlight me.

You're asking how to have an interrupt call a class method but you don't know how to implement a class method? If you don't know how to write a class, I suggest you sort that out before you start combining them with interrupts.