fields_view_base has at() observer method

Author: ashtum

include/boost/http_proto/fields_view_base.hpp

@@ -208,6 +208,36 @@ class fields_view_base
         return ph_->count;
     }
 
+    /** Return the value of a field, or throws an exception.
+
+        If more than one field with the specified name exists,
+        the first field defined by insertion order is returned.
+
+        @param id The field name constant.
+
+        @return The field value.
+
+        @throw std::out_of_range if the field is not found.
+    */
+    BOOST_HTTP_PROTO_DECL
+    core::string_view
+    at(field id) const;
+
+    /** Return the value of a field, or throws an exception.
+
+        If more than one field with the specified name exists,
+        the first field defined by insertion order is returned.
+
+        @param name The field name.
+
+        @return The field value.
+
+        @throw std::out_of_range if the field is not found.
+    */
+    BOOST_HTTP_PROTO_DECL
+    core::string_view
+    at(core::string_view name) const;
+
     /** Return true if a field exists
     */
     BOOST_HTTP_PROTO_DECL

src/fields_view_base.cpp

@@ -163,6 +163,30 @@ operator++() noexcept ->
 //
 //------------------------------------------------
 
+core::string_view
+fields_view_base::
+at(
+    field id) const
+{
+    auto const it = find(id);
+    if(it == end())
+        BOOST_THROW_EXCEPTION(
+            std::out_of_range{ "field not found" });
+    return it->value;
+}
+
+core::string_view
+fields_view_base::
+at(
+    core::string_view name) const
+{
+    auto const it = find(name);
+    if(it == end())
+        BOOST_THROW_EXCEPTION(
+            std::out_of_range{ "field not found" });
+    return it->value;
+}
+
 bool
 fields_view_base::
 exists(

test/unit/fields_view_base.cpp

@@ -172,6 +172,18 @@ struct fields_view_base_test
 
         BOOST_TEST(f.size() == 10);
 
+        // at(field)
+        // at(string_view)
+
+        BOOST_TEST(f.at("x") == "1");
+        BOOST_TEST(f.at(field::set_cookie) == "a");
+        BOOST_TEST_THROWS(
+            f.at("accept"),
+            std::out_of_range);
+        BOOST_TEST_THROWS(
+            f.at(field::accept),
+            std::out_of_range);
+
         // exists(field)
         // exists(string_view)