add gs

RCCService2018/content/LuaPackages/PurchasePrompt/strict.lua

@@ -0,0 +1,27 @@
+--[[
+	Locks a table from indexing or setting any keys that are not already defined
+
+	Useful for constants or any unchanging data, where indexing non-existent values
+	is always a mistake
+]]
+local function invalidKey(self, key)
+	local message = ("%q (%s) is not a valid member of %s"):format(
+		tostring(key),
+		typeof(key),
+		tostring(self)
+	)
+
+	error(message, 2)
+end
+
+local function strict(t, name)
+	return setmetatable(t, {
+		__index = invalidKey,
+		__newindex = invalidKey,
+		__tostring = function()
+			return name
+		end,
+	})
+end
+
+return strict