Component bslmf_ismemberobjectpointer [Package bslmf]

Provide a compile-time check for member object pointer types. More...

Classes
struct	bsl::is_member_object_pointer< t_TYPE >
struct	bsl::is_member_object_pointer< t_TYPE t_CLASS::* >
struct	bsl::is_member_object_pointer< t_TYPE t_CLASS::*const >
struct	bsl::is_member_object_pointer< t_TYPE t_CLASS::*volatile >
struct	bsl::is_member_object_pointer< t_TYPE t_CLASS::*const volatile >

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Detailed Description

Outline

• Purpose
• Classes
• Description
  • Usage
    • Example 1: Verify Member Object Pointer Types

Purpose:

Provide a compile-time check for member object pointer types.

Classes:

bsl::is_member_object_pointer	standard meta-function
bsl::is_member_object_pointer_v	the result value of the meta-function

See also:

Component bslmf_integralconstant, Component bslmf_ismemberfunctionpointer

Description:

This component defines a meta-function, bsl::is_member_object_pointer and a template variable bsl::is_member_object_pointer_v, that represents the result value of the bsl::is_member_object_pointer meta-function, that may be used to query whether a type is a pointer to non-static member object type.

bsl::is_member_object_pointer meets the requirements of the is_member_object_pointer template defined in the C++11 standard [meta.unary.cat].

Note that the template variable is_member_object_pointer_v is defined in the C++17 standard as an inline variable. If the current compiler supports the inline variable C++17 compiler feature, bsl::is_member_object_pointer_v is defined as an inline constexpr bool variable. Otherwise, if the compiler supports the variable templates C++14 compiler feature, bsl::is_member_object_pointer_v is defined as a non-inline constexpr bool variable. See BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES and BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES macros in bsls_compilerfeatures component for details.

Usage:

In this section we show intended use of this component.

Example 1: Verify Member Object Pointer Types:

Suppose that we want to assert whether a set of types are pointers to member object types.

First, we create a user-defined type MyStruct:

  struct MyStruct
  {
  };

Now, we create a typedef for a member object pointer type:

  typedef int MyStruct::* DataMemPtr;

Finally, we instantiate the bsl::is_member_object_pointer template for a non-member data type and the MyStructDataPtr type, and assert the value static data member of each instantiation:

  assert(false == bsl::is_member_object_pointer<int*>::value);
  assert(true  == bsl::is_member_object_pointer<DataMemPtr>::value);

Note that if the current compiler supports the variable templates C++14 feature then we can re-write the snippet of code above using the bsl::is_member_object_pointer_v variable as follows:

#ifdef BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES
  assert(false == bsl::is_member_object_pointer_v<int*>);
  assert(true  == bsl::is_member_object_pointer_v<DataMemPtr>);
#endif