Use memoization to avoid unnecessary renders

packages/concordia-app/src/components/TopicList/TopicListRow/index.jsx

@@ -1,27 +1,44 @@
-import React, { useContext, useEffect, useState } from 'react';
+import React, {
+  memo, useEffect, useMemo, useState,
+} from 'react';
 import { List } from 'semantic-ui-react';
 import PropTypes from 'prop-types';
 import { useDispatch, useSelector } from 'react-redux';
-import AppContext from '../../AppContext';
 import { FETCH_USER_DATABASE } from '../../../redux/actions/peerDbReplicationActions';
+import { breeze } from '../../../redux/store';
+
+const { orbit } = breeze;
 
 const TopicListRow = (props) => {
-  const { topicData, topicId } = props;
+  const { id: topicId, topicCallHash } = props;
-  const { breeze: { orbit } } = useContext(AppContext.Context);
+  const getTopicResults = useSelector((state) => state.contracts.Forum.getTopic);
-  const [topicSubject, setTopicSubject] = useState();
+  const [numberOfReplies, setNumberOfReplies] = useState(null);
+  const [username, setUsername] = useState(null);
+  const [topicAuthor, setTopicAuthor] = useState(null);
+  const [timestamp, setTimestamp] = useState(null);
+  const [topicSubject, setTopicSubject] = useState(null);
   const userAddress = useSelector((state) => state.user.address);
   const topics = useSelector((state) => state.orbitData.topics);
   const dispatch = useDispatch();
 
   useEffect(() => {
-    if (userAddress !== topicData.userAddress) {
+    if (topicCallHash && getTopicResults[topicCallHash] !== undefined) {
+      setTopicAuthor(getTopicResults[topicCallHash].value[0]);
+      setUsername(getTopicResults[topicCallHash].value[1]);
+      setTimestamp(getTopicResults[topicCallHash].value[2] * 1000);
+      setNumberOfReplies(getTopicResults[topicCallHash].value[3].length);
+    }
+  }, [getTopicResults, topicCallHash]);
+
+  useEffect(() => {
+    if (topicAuthor && userAddress !== topicAuthor) {
       dispatch({
         type: FETCH_USER_DATABASE,
         orbit,
-        userAddress: topicData.userAddress,
+        userAddress: topicAuthor,
       });
     }
-  }, [dispatch, orbit, topicData.userAddress, topicId, userAddress]);
+  }, [dispatch, topicAuthor, userAddress]);
 
   useEffect(() => {
     const topicFound = topics
@@ -32,33 +49,28 @@ const TopicListRow = (props) => {
     }
   }, [topicId, topics]);
 
-  return (
+  return useMemo(() => (
       <>
           <List.Header>
               <List.Icon name="right triangle" />
               {topicSubject && topicSubject.subject}
           </List.Header>
           <List.Content>
-              {topicData.username}
+              {username}
-              {topicData.numberOfReplies}
+              {numberOfReplies}
               {' '}
               replies
-              timestamp
+              {timestamp}
           </List.Content>
       </>
-  );
+  ), [topicSubject, username, numberOfReplies, timestamp]);
 };
 
-const TopicData = PropTypes.PropTypes.shape({
-  userAddress: PropTypes.string.isRequired,
-  username: PropTypes.string.isRequired,
-  timestamp: PropTypes.number.isRequired,
-  numberOfReplies: PropTypes.number.isRequired,
-});
-
 TopicListRow.propTypes = {
-  topicData: TopicData.isRequired,
+  id: PropTypes.number.isRequired,
-  topicId: PropTypes.number.isRequired,
+  topicCallHash: PropTypes.string.isRequired,
 };
 
-export default TopicListRow;
+TopicListRow.whyDidYouRender = true;
+
+export default memo(TopicListRow);

packages/concordia-app/src/components/TopicList/index.jsx

@@ -1,72 +1,57 @@
 import React, {
-  useCallback,
+  useEffect, useMemo, useState,
-  useContext, useEffect, useMemo, useState,
 } from 'react';
 import PropTypes from 'prop-types';
 import { useSelector } from 'react-redux';
 import { List } from 'semantic-ui-react';
 import { useHistory } from 'react-router';
-import AppContext from '../AppContext';
 import TopicListRow from './TopicListRow';
 import { PLACEHOLDER_TYPE_TOPIC } from '../../constants/PlaceholderTypes';
 import Placeholder from '../Placeholder';
 import './styles.css';
+import { drizzle } from '../../redux/store';
+
+const { contracts: { Forum: { methods: { getTopic: { cacheCall: getTopicChainData } } } } } = drizzle;
 
 const TopicList = (props) => {
   const { topicIds } = props;
-  const { drizzle: { contracts: { Forum: { methods: { getTopic } } } } } = useContext(AppContext.Context);
   const [getTopicCallHashes, setGetTopicCallHashes] = useState([]);
-  const getTopicResults = useSelector((state) => state.contracts.Forum.getTopic);
+  const drizzleInitialized = useSelector((state) => state.drizzleStatus.initialized);
-  const drizzleStatus = useSelector((state) => state.drizzleStatus);
+  const drizzleInitializationFailed = useSelector((state) => state.drizzleStatus.failed);
   const history = useHistory();
 
   useEffect(() => {
-    // TODO: is the drizzleStatus check necessary?
+    if (drizzleInitialized && !drizzleInitializationFailed) {
-    if (drizzleStatus.initialized && !drizzleStatus.failed) {
+      const newTopicsFound = topicIds
-      const newTopicPosted = topicIds
+        .filter((topicId) => !getTopicCallHashes
-        .some((topicId) => !getTopicCallHashes
           .map((getTopicCallHash) => getTopicCallHash.id)
           .includes(topicId));
 
-      if (newTopicPosted) {
+      if (newTopicsFound.length > 0) {
-        setGetTopicCallHashes(topicIds.map((topicId) => {
+        setGetTopicCallHashes([
-          const foundGetTopicCallHash = getTopicCallHashes.find((getTopicCallHash) => getTopicCallHash.id === topicId);
+          ...getTopicCallHashes,
-
+          ...newTopicsFound
-          if (foundGetTopicCallHash !== undefined) {
+            .map((topicId) => ({
-            return ({ ...foundGetTopicCallHash });
-          }
-
-          return ({
               id: topicId,
-            hash: getTopic.cacheCall(topicId),
+              hash: getTopicChainData(topicId),
-          });
+            })),
-        }));
+        ]);
       }
     }
-  }, [drizzleStatus.failed, drizzleStatus.initialized, getTopic, getTopicCallHashes, topicIds]);
+  }, [drizzleInitializationFailed, drizzleInitialized, getTopicCallHashes, topicIds]);
-
-  const handleTopicClick = useCallback((topicId) => {
-    history.push(`/topics/${topicId}`);
-  }, [history]);
 
   const topics = useMemo(() => topicIds
     .map((topicId) => {
-      const getTopicHash = getTopicCallHashes.find((getTopicCallHash) => getTopicCallHash.id === topicId);
+      const topicHash = getTopicCallHashes.find((getTopicCallHash) => getTopicCallHash.id === topicId);
 
-      if (getTopicHash && getTopicResults[getTopicHash.hash] !== undefined) {
+      const handleTopicClick = () => {
-        const topicData = {
+        history.push(`/topics/${topicId}`);
-          userAddress: getTopicResults[getTopicHash.hash].value[0],
-          username: getTopicResults[getTopicHash.hash].value[1],
-          timestamp: getTopicResults[getTopicHash.hash].value[2] * 1000,
-          numberOfReplies: getTopicResults[getTopicHash.hash].value[3].length,
       };
 
+      if (topicHash) {
         return (
-            <List.Item key={topicId} className="list-item" name={topicId} onClick={() => handleTopicClick(topicId)}>
+            <List.Item key={topicId} className="list-item" name={topicId} onClick={handleTopicClick}>
-                <TopicListRow
+                <TopicListRow id={topicId} topicCallHash={topicHash.hash} />
-                  topicData={topicData}
-                  topicId={topicId}
-                />
             </List.Item>
         );
       }
@@ -79,7 +64,7 @@ const TopicList = (props) => {
               />
           </List.Item>
       );
-    }), [getTopicCallHashes, getTopicResults, handleTopicClick, topicIds]);
+    }), [getTopicCallHashes, history, topicIds]);
 
   return (
       <List selection divided id="topic-list" size="big">
@@ -92,4 +77,6 @@ TopicList.propTypes = {
   topicIds: PropTypes.arrayOf(PropTypes.number).isRequired,
 };
 
+TopicList.whyDidYouRender = true;
+
 export default TopicList;

packages/concordia-app/src/layouts/MainLayout/index.jsx

@@ -1,6 +1,5 @@
 import React from 'react';
 import PropTypes from 'prop-types';
-
 import MainLayoutMenu from './MainLayoutMenu';
 
 const MainLayout = (props) => {

packages/concordia-app/src/views/Home/Board/index.jsx

@@ -46,4 +46,6 @@ Board.propTypes = {
   numberOfTopics: PropTypes.number.isRequired,
 };
 
+Board.whyDidYouRender = true;
+
 export default Board;

packages/concordia-app/src/views/Home/index.jsx

@@ -1,31 +1,34 @@
 import React, {
-  useContext, useEffect, useMemo, useState,
+  memo, useEffect, useMemo, useState,
 } from 'react';
 import { Container } from 'semantic-ui-react';
 import { useSelector } from 'react-redux';
-import AppContext from '../../components/AppContext';
 import Board from './Board';
 import './styles.css';
+import { drizzle } from '../../redux/store';
+
+const { contracts: { Forum: { methods: { getNumberOfTopics } } } } = drizzle;
 
 const Home = () => {
-  const { drizzle: { contracts: { Forum: { methods: { getNumberOfTopics } } } } } = useContext(AppContext.Context);
   const [numberOfTopicsCallHash, setNumberOfTopicsCallHash] = useState('');
   const getNumberOfTopicsResults = useSelector((state) => state.contracts.Forum.getNumberOfTopics);
 
   useEffect(() => {
     setNumberOfTopicsCallHash(getNumberOfTopics.cacheCall());
-  }, [getNumberOfTopics]);
+  }, []);
 
   const numberOfTopics = useMemo(() => (getNumberOfTopicsResults[numberOfTopicsCallHash] !== undefined
     ? parseInt(getNumberOfTopicsResults[numberOfTopicsCallHash].value, 10)
     : null),
   [getNumberOfTopicsResults, numberOfTopicsCallHash]);
 
-  return (
+  return useMemo(() => (
       <Container id="home-container" textAlign="center">
           {numberOfTopics !== null && <Board numberOfTopics={numberOfTopics} />}
       </Container>
-  );
+  ), [numberOfTopics]);
 };
 
-export default Home;
+Home.whyDidYouRender = true;
+
+export default memo(Home);

packages/concordia-app/src/views/Topic/TopicCreate/index.jsx

@@ -1,5 +1,5 @@
 import React, {
-  useCallback, useContext, useEffect, useState,
+  useCallback, useEffect, useState,
 } from 'react';
 import {
   Button, Container, Form, Icon, Input, TextArea,
@@ -7,30 +7,16 @@ import {
 import { useTranslation } from 'react-i18next';
 import { useHistory } from 'react-router';
 import { useSelector } from 'react-redux';
-import AppContext from '../../../components/AppContext';
 import './styles.css';
+import { drizzle, breeze } from '../../../redux/store';
+
+const { contracts: { Forum: { methods: { createTopic } } } } = drizzle;
+const { orbit: { stores } } = breeze;
 
 const TopicCreate = (props) => {
   const { account } = props;
-
-  const {
-    drizzle: {
-      contracts: {
-        Forum: {
-          methods: { createTopic },
-        },
-      },
-    },
-    breeze: {
-      orbit: {
-        stores,
-      },
-    },
-  } = useContext(AppContext.Context);
-
   const transactionStack = useSelector((state) => state.transactionStack);
   const transactions = useSelector((state) => state.transactions);
-
   const [subjectInput, setSubjectInput] = useState('');
   const [messageInput, setMessageInput] = useState('');
   const [topicSubjectInputEmptySubmit, setTopicSubjectInputEmptySubmit] = useState(false);

packages/concordia-app/src/views/Topic/index.jsx

@@ -16,4 +16,6 @@ const Topic = () => {
     );
 };
 
+Topic.whyDidYouRender = true;
+
 export default Topic;