add gs

RCCService2018/content/LuaPackages/PurchasePrompt/createEnum.lua

@@ -0,0 +1,58 @@
+--[[
+	An implementation of an enumerated type in Lua. Creates enumerated
+	types with uniquely identifiable values (using symbol)
+
+	Note that resulting enum object does not associate ordinals with its
+	values, and cannot be iterated through. It can, however, test if a provided
+	value is a member of its set of values with the `isMember` function
+
+	This is valuable for the purchase prompt because it relies heavily on
+	enumerated values to determine things like state and which errors occurred.
+]]
+local Symbol = require(script.Parent.Symbol)
+
+local strict = require(script.Parent.strict)
+
+--[[
+	Returns a new enum type with the given name.
+]]
+local function createEnum(enumName, values)
+	assert(typeof(enumName) == "string", "Bad argument #1, expected string")
+	assert(typeof(values) == "table", "Bad argument #2, expected list of values")
+
+	local enumInternal = {}
+
+	for _, valueName in ipairs(values) do
+		assert(valueName ~= "isMember", "Shadowing 'isMember' function is not allowed")
+		assert(typeof(valueName) == "string", "Only string names are supported for enum types")
+
+		local enumValue = Symbol.named(valueName)
+		local asString = ("%s.%s"):format(enumName, valueName)
+		getmetatable(enumValue).__tostring = function()
+			return asString
+		end
+
+		enumInternal[valueName] = enumValue
+	end
+
+	function enumInternal.isMember(value)
+		if typeof(value) ~= "userdata" then
+			return false
+		end
+
+		for _, enumeratedValue in pairs(enumInternal) do
+			if value == enumeratedValue then
+				return true
+			end
+		end
+
+		return false
+	end
+
+	local enum = newproxy(true)
+	getmetatable(enum).__index = enumInternal
+
+	return strict(enumInternal, enumName)
+end
+
+return createEnum