.. _program_listing_file_include_opentelemetry_trace_propagation_composite_propagator.h:

Program Listing for File composite_propagator.h
===============================================

|exhale_lsh| :ref:`Return to documentation for file <file_include_opentelemetry_trace_propagation_composite_propagator.h>` (``include/opentelemetry/trace/propagation/composite_propagator.h``)

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

.. code-block:: cpp

   #include <initializer_list>
   #include <memory>
   #include <vector>
   #include "opentelemetry/trace/propagation/text_map_propagator.h"
   
   OPENTELEMETRY_BEGIN_NAMESPACE
   namespace trace
   {
   namespace propagation
   {
   
   template <typename T>
   class CompositePropagator : public TextMapPropagator<T>
   {
   public:
     CompositePropagator(std::vector<std::unique_ptr<TextMapPropagator<T>>> propagators)
         : propagators_(std::move(propagators))
     {}
     // Rules that manages how context will be extracted from carrier.
     using Getter = nostd::string_view (*)(const T &carrier, nostd::string_view trace_type);
   
     // Rules that manages how context will be injected to carrier.
     using Setter = void (*)(T &carrier,
                             nostd::string_view trace_type,
                             nostd::string_view trace_description);
   
     void Inject(Setter setter, T &carrier, const context::Context &context) noexcept override
     {
       for (auto &p : propagators_)
       {
         p->Inject(setter, carrier, context);
       }
     }
   
     context::Context Extract(Getter getter,
                              const T &carrier,
                              context::Context &context) noexcept override
     {
       auto first = true;
       context::Context tmp_context;
       for (auto &p : propagators_)
       {
         if (first)
         {
           tmp_context = p->Extract(getter, carrier, context);
           first       = false;
         }
         else
         {
           tmp_context = p->Extract(getter, carrier, tmp_context);
         }
       }
       return propagators_.size() ? tmp_context : context;
     }
   
   private:
     std::vector<std::unique_ptr<TextMapPropagator<T>>> propagators_;
   };
   }  // namespace propagation
   }  // namespace trace
   OPENTELEMETRY_END_NAMESPACE;