Extract useRoomState hook into hooks directory

src/components/views/right_panel/PinnedMessagesCard.tsx

@@ -28,6 +28,7 @@ import { useEventEmitter } from "../../../hooks/useEventEmitter";
 import PinningUtils from "../../../utils/PinningUtils";
 import { useAsyncMemo } from "../../../hooks/useAsyncMemo";
 import PinnedEventTile from "../rooms/PinnedEventTile";
+import { useRoomState } from "../../../hooks/useRoomState";
 
 interface IProps {
     room: Room;
@@ -75,24 +76,6 @@ export const useReadPinnedEvents = (room: Room): Set<string> => {
     return readPinnedEvents;
 };
 
-const useRoomState = <T extends any>(room: Room, mapper: (state: RoomState) => T): T => {
-    const [value, setValue] = useState<T>(room ? mapper(room.currentState) : undefined);
-
-    const update = useCallback(() => {
-        if (!room) return;
-        setValue(mapper(room.currentState));
-    }, [room, mapper]);
-
-    useEventEmitter(room?.currentState, "RoomState.events", update);
-    useEffect(() => {
-        update();
-        return () => {
-            setValue(undefined);
-        };
-    }, [update]);
-    return value;
-};
-
 const PinnedMessagesCard = ({ room, onClose }: IProps) => {
     const cli = useContext(MatrixClientContext);
     const canUnpin = useRoomState(room, state => state.mayClientSendStateEvent(EventType.RoomPinnedEvents, cli));

src/hooks/useRoomState.ts

@@ -0,0 +1,40 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { useCallback, useEffect, useState } from "react";
+import { Room } from "matrix-js-sdk/src/models/room";
+import { RoomState } from "matrix-js-sdk/src/models/room-state";
+
+import { useEventEmitter } from "./useEventEmitter";
+
+// Hook to simplify watching Matrix Room state
+export const useRoomState = <T extends any>(room: Room, mapper: (state: RoomState) => T): T => {
+    const [value, setValue] = useState<T>(room ? mapper(room.currentState) : undefined);
+
+    const update = useCallback(() => {
+        if (!room) return;
+        setValue(mapper(room.currentState));
+    }, [room, mapper]);
+
+    useEventEmitter(room?.currentState, "RoomState.events", update);
+    useEffect(() => {
+        update();
+        return () => {
+            setValue(undefined);
+        };
+    }, [update]);
+    return value;
+};