Error: Create Error Object with {fmt}

error/CMakeLists.txt

@@ -5,11 +5,14 @@ project(error)
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Wnon-virtual-dtor -Wpedantic")
 set(CMAKE_CXX_STANDARD 11)
 
+include(cmake/CPM.cmake)
+cpmaddpackage("gh:fmtlib/fmt#10.0.0")
+
 add_library(error src/error.cpp)
 target_include_directories(error PUBLIC include)
+target_link_libraries(error PUBLIC fmt)
 
 if(CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
-  include(cmake/CPM.cmake)
   cpmaddpackage("gh:TheLartians/[email protected]")
 
   if(BUILD_TESTING)

error/include/error/error.hpp

@@ -1,6 +1,10 @@
 #pragma once
 
+#include <fmt/core.h>
+
 #include <exception>
+#include <string>
+#include <utility>
 
 namespace error {
 
@@ -9,14 +13,18 @@ namespace error {
  */
 class Error : public std::exception {
  private:
-  const char* message; /**< The error message. */
+  std::string message; /**< The error message. */
 
  public:
   /**
-   * @brief Constructs a new error with the given message.
-   * @param message An error message.
+   * @brief Constructs a new error with the given format for the message.
+   * @tparam T Variadic template parameter pack for format arguments.
+   * @param fmt A format string for the message.
+   * @param args Format arguments.
    */
-  Error(const char* message);
+  template <typename... T>
+  Error(fmt::format_string<T...> fmt, T&&... args)
+      : message(fmt::format(fmt, std::forward<T>(args)...)) {}
 
   /**
    * @brief Returns the explanatory string.

error/src/error.cpp

@@ -2,8 +2,6 @@
 
 namespace error {
 
-Error::Error(const char* message) : message(message) {}
-
-const char* Error::what() const noexcept { return message; }
+const char* Error::what() const noexcept { return message.c_str(); }
 
 }  // namespace error

error/test/error_test.cpp

@@ -3,8 +3,15 @@
 #include <string>
 
 TEST_CASE("Error Construction") {
-  const error::Error err("unknown error");
-  REQUIRE(std::string("unknown error") == err.what());
+  SECTION("With one argument") {
+    const error::Error err("unknown error");
+    REQUIRE(std::string("unknown error") == err.what());
+  }
+
+  SECTION("With one or more arguments") {
+    const error::Error err("HTTP error {}", 404);
+    REQUIRE(std::string("HTTP error 404") == err.what());
+  }
 }
 
 TEST_CASE("Error Throwing and Catching") {