Component bslmf_isaccessiblebaseof [Package bslmf]

Provide a compile-time check for derived classes. More...

Namespaces
namespace	bslmf

---

Detailed Description

Outline

• Purpose
• Classes
• Description
  • Usage
    • Example 1: Base And Derived Classes
    • Example 2: Unrelated Classes

Purpose:

Provide a compile-time check for derived classes.

Classes:

bslmf::IsAccessibleBaseOf

meta-function for detecting derived classes

Description:

This component provides a meta-function, bslmf::IsAccessibleBaseOf, that determines whether one class is an accessible base class of another class. The static constant bslmf::IsAccessibleBaseOf::value is true if the template parameter t_BASE class is an accessible base class of, or the same class as, the template parameter t_DERIVED. Otherwise, bslmf::IsAccessibleBaseOf::value is false. The specific cases of private, protected, and ambiguous inheritance are not supported for versions of C++ prior to 11.

Usage:

In this section we show intended use of this component.

Example 1: Base And Derived Classes:

Define two classes, one inheriting from the other.

  struct Base
  {};

  struct Derived : Base
  {};

Evaluate bslmf::IsAccessibleBaseOf::value.

  void example1()
  {
      assert((true  == bslmf::IsAccessibleBaseOf<Base,    Derived>::value));
      assert((true  == bslmf::IsAccessibleBaseOf<Base,    Base>   ::value));
      assert((true  == bslmf::IsAccessibleBaseOf<Derived, Derived>::value));
      assert((false == bslmf::IsAccessibleBaseOf<Derived, Base>   ::value));
  }

Example 2: Unrelated Classes:

Define two classes, one inheriting privately from the other.

  class Unrelated
  {};

  class Unrelated2
  {};

Evaluate bslmf::IsAccessibleBaseOf::value. Note that Derived is not observably derived from Base, so std::is_base_of would evaluate true, but bslmf::IsAccessibleBaseOf evaluates false.

  void example2()
  {
      assert((false ==
              bslmf::IsAccessibleBaseOf<Unrelated, Unrelated2>::value));
  }