work.dart

mixin Activity{  
  void caloriesLeft(doble totalCalories,double  burnedCalories){
      return totalCalories-burnedCalories;
  }
}

// our main class- this is just an example
// please make seperate file for mixin
class Person with Activity{
   double totalCalories=200;
   double burnedCalories=20;
  
  
   // call the method here in this class,
   // because we have injected it using "with" keyword.

   totalcalories= caloriesLeft(totalCalories,burnedCalories);
}