.. _program_listing_file_include_opentelemetry_common_key_value_iterable.h:

Program Listing for File key_value_iterable.h
=============================================

|exhale_lsh| :ref:`Return to documentation for file <file_include_opentelemetry_common_key_value_iterable.h>` (``include/opentelemetry/common/key_value_iterable.h``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   #pragma once
   
   #include "opentelemetry/common/attribute_value.h"
   #include "opentelemetry/nostd/function_ref.h"
   #include "opentelemetry/version.h"
   
   OPENTELEMETRY_BEGIN_NAMESPACE
   namespace common
   {
   class KeyValueIterable
   {
   public:
     virtual ~KeyValueIterable() = default;
   
     virtual bool ForEachKeyValue(nostd::function_ref<bool(nostd::string_view, common::AttributeValue)>
                                      callback) const noexcept = 0;
   
     virtual size_t size() const noexcept = 0;
   };
   
   //
   // NULL object pattern empty iterable.
   //
   class NullKeyValueIterable : public KeyValueIterable
   {
   public:
     NullKeyValueIterable(){};
   
     virtual bool ForEachKeyValue(
         nostd::function_ref<bool(nostd::string_view, common::AttributeValue)>) const noexcept
     {
       return true;
     };
   
     virtual size_t size() const noexcept { return 0; }
   };
   
   }  // namespace common
   OPENTELEMETRY_END_NAMESPACE