rspec/rules/S6027/rule.adoc

``++const++`` member functions are the member functions that do not modify the object they are called on.

 While returning a non-const reference or a pointer from such a function does not in itself modify the object, it creates an opportunity for modification in the future. In particular, it enables the code that uses this member function to modify a ``++const++`` object.


When defining a const member function, consider returning by reference/pointer to ``++const++`` or returning by value.


In some cases you need to be able to read the field from ``++const++`` objects and mutate it in non-``++const++``, as is often the case with container objects, like ``++std::vector++``. Consider using ``++const++``-overloading in this case.


This rule detects when a ``++const++`` member function returns a reference field and has as a return type a pointer/reference to a non-const object.


== Noncompliant Code Example

----
class Person {
  std::string name;
  std::string &alias = name;
public:
  std::string &getAlias() const { // Noncompliant
    return alias;
  }
};

void fun(const Person &p) {
  p.getAlias() = "Looser"; // The function modifies a constant object
}

class Shadow {
  Person &p;
public:
  Shadow(Person &p) : p(p) {}
  Person &getPerson() const {// Noncompliant
    return p;
  }
};
----


== Compliant Solution

 

----
class Person {
  std::string name;
  std::string &alias = name;
public:
  std::string const &getAlias() const { // Compliant
    return alias;
  }
};

void fun(const Person &p) {
  //p.getAlias() = "Looser"; // This prank is prevented
}

class Shadow {
  Person &p;
public:
  Shadow(Person &p) : p(p) {}
  Person const &getPerson() const {// Compliant
    return p;
  }
  Person &getPerson() {// Compliant, const-overload
    return p;
  }
};
----


== See

* https://isocpp.org/wiki/faq/const-correctness#return-const-ref-from-const-memfn