refactor: improve and make more efficient some Message API (#432)

tests/integrationtests/DBusGeneralTests.cpp

@@ -44,6 +44,7 @@ using ::testing::ElementsAre;
 using ::testing::Eq;
 using namespace std::chrono_literals;
 using namespace sdbus::test;
+using namespace std::string_view_literals;
 
 using ADirectConnection = TestFixtureWithDirectConnection;
 
@@ -157,7 +158,7 @@ TYPED_TEST(AConnection, WillNotPassToMatchCallbackMessagesThatDoNotMatchTheRule)
     std::atomic<size_t> numberOfMatchingMessages{};
     auto slot = this->s_proxyConnection->addMatch(matchRule, [&](sdbus::Message msg)
     {
-        if(msg.getMemberName() == "simpleSignal")
+        if(msg.getMemberName() == "simpleSignal"sv)
             numberOfMatchingMessages++;
     });
     auto adaptor2 = std::make_unique<TestAdaptor>(*this->s_adaptorConnection, OBJECT_PATH_2);

tests/unittests/Message_test.cpp

@@ -32,8 +32,10 @@
 #include <list>
 
 using ::testing::Eq;
+using ::testing::StrEq;
 using ::testing::Gt;
 using ::testing::DoubleEq;
+using ::testing::IsNull;
 using namespace std::string_literals;
 
 namespace
@@ -465,11 +467,10 @@ TEST(AMessage, CanPeekASimpleType)
     msg << 123;
     msg.seal();
 
-    std::string type;
-    std::string contents;
-    msg.peekType(type, contents);
-    ASSERT_THAT(type, "i");
-    ASSERT_THAT(contents, "");
+    auto [type, contents] = msg.peekType();
+
+    ASSERT_THAT(type, Eq('i'));
+    ASSERT_THAT(contents, IsNull());
 }
 
 TEST(AMessage, CanPeekContainerContents)
@@ -478,11 +479,10 @@ TEST(AMessage, CanPeekContainerContents)
     msg << std::map<int, std::string>{{1, "one"}, {2, "two"}};
     msg.seal();
 
-    std::string type;
-    std::string contents;
-    msg.peekType(type, contents);
-    ASSERT_THAT(type, "a");
-    ASSERT_THAT(contents, "{is}");
+    auto [type, contents] = msg.peekType();
+
+    ASSERT_THAT(type, Eq('a'));
+    ASSERT_THAT(contents, StrEq("{is}"));
 }
 
 TEST(AMessage, CanCarryDBusArrayGivenAsCustomType)