From 39798db6b8669a8d3b4605a0bc8bb70d65f0b0aa Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sun, 4 Aug 2024 13:02:38 +0100
Subject: Help exception class for lazy/cached message content

---
 lib/msgException.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 lib/msgException.h

(limited to 'lib')

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;
+};
-- 
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