Re: & operator (in parameters) and const

Hi Jack,


I'm not entirely sure I understand what you mean, but here are some
examples of how to use references and const in methods.

class Person
{
private:
  int m_age;

public:
  Person(int age) : m_age(age)
  {
  }

  void setAge(int age)
  {
     m_age = age;
  }

  int getAge() const
  {
     return m_age;
  }
};

void GrowOlder(Person& person)
{
  person.setAge(person.getAge() + 1);
}

int main()
{
  Person p1(10);
  GrowOlder(p1);
  // p1.m_age is now 11

  const Person p2(100);
  p2.getAge(); // OK, because getAge is const
  p2.setAge(99); // Error, because setAge is non-const and p2 is const
}

So, marking a method as const makes it possible for clients to call it on
const instances of the class. The compiler also checks that a const method
does not modify the state of the object, so you can't write to m_age from
getAge() in the example above.

References are used to let a function modify one of its arguments. By
making the person argument a reference in GrowOlder above, we can modify
the actual person passed in at the call site.

Hope that helps.

--
Best Regards,
Kim Gr?sman