add gs

RCCService2018/content/LuaPackages/RoactImpl/PureComponent.lua

@@ -0,0 +1,41 @@
+--[[
+	A version of Component with a `shouldUpdate` method that forces the
+	resulting component to be pure.
+]]
+
+local Component = require(script.Parent.Component)
+
+local PureComponent = Component:extend("PureComponent")
+
+-- When extend()ing a component, you don't get an extend method.
+-- This is to promote composition over inheritance.
+-- PureComponent is an exception to this rule.
+PureComponent.extend = Component.extend
+
+function PureComponent:shouldUpdate(newProps, newState)
+	-- In a vast majority of cases, if state updated, something has updated.
+	-- We don't bother checking in this case.
+	if newState ~= self.state then
+		return true
+	end
+
+	if newProps == self.props then
+		return false
+	end
+
+	for key, value in pairs(newProps) do
+		if self.props[key] ~= value then
+			return true
+		end
+	end
+
+	for key, value in pairs(self.props) do
+		if newProps[key] ~= value then
+			return true
+		end
+	end
+
+	return false
+end
+
+return PureComponent