Help exception class for lazy/cached message content

1 files changed, 23 insertions, 0 deletions

diff --git a/lib/msgException.h b/lib/msgException.h
new file mode 100644
index 0000000..660738d
--- /dev/null
+++ b/lib/msgException.h
@@ -0,0 +1,23 @@
+#pragma once
+
+#include <optional>
+#include <string>
+
+template<typename BaseException> class MsgException : public BaseException {
+protected:
+	using BaseException::BaseException;
+	[[nodiscard]] virtual std::string getMsg() const noexcept = 0;
+
+public:
+	[[nodiscard]] const char *
+	what() const noexcept override
+	{
+		if (!msg) {
+			msg.emplace(getMsg());
+		}
+		return msg->c_str();
+	}
+
+private:
+	mutable std::optional<std::string> msg;
+};