feat: initial commit

src/observe.luau

@@ -0,0 +1,38 @@
+local atom = require(script.Parent.atom)
+type Atom<T> = atom.Atom<T>
+
+local subscribe = require(script.Parent.subscribe)
+
+local function observe<Item, Key>(atom: Atom<{ [Key]: Item }>, factory: (value: Item, key: Key) -> () -> ()): (() -> (), () -> ())
+	local connections: { [Key]: () -> () } = {}
+
+	local function update(state: { [Key]: Item })
+		for key, disconnect in connections do
+			if state[key] == nil then
+				connections[key] = nil
+				disconnect()
+			end
+		end
+
+		for key, value in state do
+			if not connections[key] then
+				connections[key] = factory(value, key)
+			end
+		end
+	end
+
+	local unsubscribe, flush = subscribe(atom, update)
+
+	local function cleanup()
+		unsubscribe()
+		for _, disconnect in connections do
+			disconnect()
+		end
+	end
+
+	update(atom:get())
+
+	return cleanup, flush
+end
+
+return observe