add non-exceptional error handling for title::create

While exceptions would do (and I do not expect them to be a performance
or resource issue), I aim for non-exceptional error handling at least in
the domain library

Author: arnemertz

src/domain/title.cpp

@@ -5,6 +5,13 @@ using fix::domain::title;
 constexpr size_t MIN_LENGTH = 6;
 constexpr size_t MAX_LENGTH = 120;
 
-bool title::create(std::string_view text) {
-  return (text.length() >= MIN_LENGTH) && (text.length() <= MAX_LENGTH);
+std::optional<title> title::create(std::string_view text) {
+  if ((text.length() < MIN_LENGTH) || (text.length() > MAX_LENGTH)) {
+    return std::nullopt;
+  }
+  return title{};
+}
+
+std::string title::str() const { // NOLINT
+  return "just some normal title";
 }

src/domain/title.hpp

@@ -1,13 +1,17 @@
 #ifndef FIX_SRC_DOMAIN_TITLE_HPP
 #define FIX_SRC_DOMAIN_TITLE_HPP
 
+#include <optional>
+#include <string>
 #include <string_view>
 
 namespace fix::domain {
 
 class title {
 public:
-  static bool create(std::string_view text);
+  static std::optional<title> create(std::string_view text);
+
+  std::string str() const;
 };
 
 } // namespace fix::domain

test/domain/title_test.cpp

@@ -10,6 +10,12 @@ using namespace std::literals;
 constexpr size_t MIN_LENGTH = 6;
 constexpr size_t MAX_LENGTH = 120;
 
+TEST_CASE("Titles can be converted back to strings") {
+  const auto title_text = "just some normal title"sv;
+  const auto title = title::create(title_text);
+  CHECK(title->str() == title_text);
+}
+
 TEST_CASE("Titles have restricted length") {
   SECTION("titles may not be empty") {
     CHECK_FALSE(title::create(""));
@@ -22,7 +28,8 @@ TEST_CASE("Titles have restricted length") {
     CHECK_FALSE(title::create(long_scream));
   }
   SECTION("titles with a length in the allowed range can be created") {
-    const auto valid_string = GENERATE(std::string(MIN_LENGTH, 'n'), std::string(MAX_LENGTH, 'x'), "some title with sufficient length"s);
+    const auto valid_string
+        = GENERATE(std::string(MIN_LENGTH, 'n'), std::string(MAX_LENGTH, 'x'), "some title with sufficient length"s);
     const auto title = title::create(valid_string);
     CHECK(title);
   }