rspec/rules/S5414/cfamily/rule.adoc

Mixing (non-const) ``++public++`` and ``++private++`` data members is a bad practice because it causes confusion about the intention of the class:

* If the class is a collection of loosely related values, all the data members should be ``++public++``.
* On the other hand, if the class is trying to maintain an invariant, all the data members should be ``++private++``.

If we mix data members with different levels of accessibility, the purpose of the class is muddled.


== Noncompliant Code Example

[source,cpp]
----
class MyClass // Noncompliant
{
public:
  int firstNumber1() const { return firstNumber; }
  void setFirstNumber(int firstNumber) { this->firstNumber = firstNumber; }
  int secondNumber = 2;
  const int constNumber = 0; // const data members are fine
private:
  int firstNumber = 1;
};
----


== Compliant Solution

[source,cpp]
----
class MyClass // Depending on the case, the solution might be different. Here, since this class does not enforce any invariant, we make all the data members public
{
public:
  int firstNumber;
  int secondNumber;
  const int constNumber = 0;
};
----


== Exceptions

Since ``++const++`` data members cannot be modified, it's not breaking encapsulation to make a const value public, even in a class that enforces an invariant.


== See

* https://github.com/isocpp/CppCoreGuidelines/blob/036324/CppCoreGuidelines.md#c134-ensure-all-non-const-data-members-have-the-same-access-level[{cpp} Core Guidelines C.134]: Ensure all non-const data members have the same access level
* https://github.com/isocpp/CppCoreGuidelines/blob/036324/CppCoreGuidelines.md#c9-minimize-exposure-of-members[{cpp} Core Guidelines C.9]: Minimize exposure of members


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