Edit. I rewrote the code to be even more minimalist. The below code is a spike test of my issue.
Here is a video of the issue:
https://imgur.com/a/WI2wHMl
I have two components.
The first component is named TextEditor (and it is a text editor) but its content is irrelevant - the component could be anything. A simple div with text would be just as relevant.
The next component is named Workflows and is used to render a collection from IndexDB (using the Dexie.js library). I named this collection "workflows" and the state variable I store them in is named workflows_list_array
What I am trying to do is the following:
When the page loads, I want to check if any workflows have a specific ID . If they do, I store them in workflows_list_array and render them. I don't need help with this part.
However, if no workflows with the aforementioned criteria exist, I want to keep the component named Workflows hidden and render the component named TextEditor. If workflows do exist, I want the TextEditor hidden and to display Workflows
The problem is that even though I have it working, when workflows do exist (when workflows_list_array is populated) the TextEditor "flickers" briefly before being hidden and then the Workflows component is displayed.
I can tell this is an async issue but I can't tell how to fix it.
I posted code below and I tried to keep it to a minimum.
Test.js
import React, {useState, useEffect} from "react";
import db from "../services"
function Workflows(props){
return (
<div>
<ul>
{
props.workflows.map((val,index)=>{
return <li key={index}>{val.content}</li>
})
}
</ul>
</div>
)
}
function TextEditor(){
return (
<div> TextEditor </div>
)
}
function Test(props){
let [workflows_list_array, set_state_of_workflows_list_array] = useState([]);
let [client_id_number, set_client_id_number] = useState(5);
useEffect(() => { // get all workflows of the selected client per its ID
db.workflows.toArray((workflows_list)=>{ // iterate through workflows array
return workflows_list
}).then((workflows_list)=>{
workflows_list.forEach((val)=>{
if(client_id_number === val.client_id){
set_state_of_workflows_list_array((prev)=>{
return [...prev, val]
});
}
});
});
}, []);
return(
<div>
{workflows_list_array.length ? null : <TextEditor/> }
{workflows_list_array.length ? <Workflows workflows={workflows_list_array}/> : null}
</div>
)
}
export default Test
services.js
import Dexie from 'dexie';
import 'dexie-observable';
var workflowMagicUserDB = new Dexie("WorkflowMagicUserDB");
workflowMagicUserDB.version(1).stores({
user: "",
workflows: "++id,client_id,content,title",
clients: "++id,name",
calendar_events: "++id,start,end,title"
});
export default workflowMagicUserDB
Why don't you include a flag which indicates if you have already got data from IndexDB, something like:
function Test(props){
const [loading, setLoading] = React.useState(true);
let [workflows_list_array, set_state_of_workflows_list_array] = useState([]);
let [client_id_number, set_client_id_number] = useState(5);
useEffect(() => {
db.workflows.toArray((workflows_list)=>{
}).then((workflows_list)=>{
}).finally(() => setLoading(false)); //when process finishes, it will update the state, at that moment it will render TextEditor or Workflows
}, []);
if(loading) return <LoadingIndicator/>; // or something else which indicates the app is fetching or processing data
return(
<div>
{workflows_list_array.length ? null : <TextEditor/> }
{workflows_list_array.length ? <Workflows workflows={workflows_list_array}/> : null}
</div>
)
}
export default Test
When the process finishes, finally will be executed and set loading state to false, after that, your app will render TextEditor or Workflows
Related
I have been trying to add "no records found" message after running a search for worker names. But I have not been successful. I either get 20 "no records found" messages or none at all. I am not sure what I am doing wrong, but I have been trying for last 4 hours various methods and work arounds.
I know that this should be simple to implement, but it has been difficult.
Here is a link to my code on codesandbox: https://codesandbox.io/s/fe-hatc-ass-search-n62kw?file=/src/App.js
Any insights would be helpful....
Things I tried were, if else statements, logical operators... etc...
In my opinion the first thing you need to think about is what data do you need and when do you need it. To display no results like you want you are going to need the workers name in the component that is doing the filtering. So you would need it in the orders component. I would merge the worker data with the order data and then you can just filter and manipulate the data after that. That would also stop you from making an api request every time someone changes the input and all you need to do is filter the already fetched data. Then you can check the array length and if it is greater than 0 you can display results else display a no results statement.
So something like the following:
Orders component
import React, { useEffect, useState } from "react";
import "./Orders.css";
import Order from "./Worker";
import axios from "axios";
const Orders = () => {
const [orders, setOrders] = useState([]);
const [results, setResults] = useState([]);
const [searchedWorker, setSearchedWorker] = useState("");
const getOrders = async () => {
const workOrders = await axios.get(
"https://api.hatchways.io/assessment/work_orders"
);
const mappedOrders = await Promise.all(workOrders.data.orders.map(async order => {
const worker = await axios.get(
`https://api.hatchways.io/assessment/workers/${order.workerId}`
);
return {...order, worker: worker.data.worker}
}))
setOrders(mappedOrders);
};
useEffect(() => {
getOrders();
}, []);
useEffect(() => {
const filtered = orders.filter(order => order.worker.name.toLowerCase().includes(searchedWorker));
setResults(filtered)
}, [searchedWorker, orders])
return (
<div>
<h1>Orders</h1>
<input
type="text"
name="workerName"
id="workerName"
placeholder="Filter by workername..."
value={searchedWorker} //property specifies the value associated with the input
onChange={(e) => setSearchedWorker(e.target.value.toLowerCase())}
//onChange captures the entered values and stores it inside our state hooks
//then we pass the searched values as props into the component
/>
<p>Results: {results.length}</p>
{results.length > 0 ? results.map((order) => (
<Order key={order.id} lemon={order} />
)) : <p>No results found</p> }
</div>
);
};
//(if this part is true) && (this part will execute)
//is short for: if(condition){(this part will execute)}
export default Orders;
Then you can simplify your single order component
import React from "react";
const Order = ({ lemon }) => {
return (
<div>
<div className="order">
<p>Work order {lemon.id}</p>
<p>{lemon.description}</p>
<img src={`${lemon.worker.image}`} alt="worker" />
<p>{lemon.worker.name}</p>
<p>{lemon.worker.company}</p>
<p>{lemon.worker.email}</p>
<p>{new Date(lemon.deadline).toLocaleString()}</p>
</div>
</
div>
);
};
export default Order;
Looking at your code, the problem is because you're doing the filtering in each individual <Order> component. The filtering should be done in the parent Orders component and you should only render an <Order> component if a match is found.
Currently, your <Order> component is rendering, even if there's no match.
You could add an state in the Orders.js to count how many items are being presented. However, since each Worker depends on an api call, you would need to have the response (getWorker, in Workers.js) wait for the response in order to make the count. Every time the input value changes, you should reset the counter to 0.
https://codesandbox.io/s/fe-hatc-ass-search-forked-elyjz?file=/src/Worker.js:267-276
Also, as a comment, it is safer to put the functions that are run in useEffect, inside the useEffect, this way it is easier to see if you are missing a dependency.
I'm working on a site where I have a gallery and custom build lightbox. Currently, I'm querying my data with a page query, however, I also use them in other components to display the right images and changing states. It is easier for me to store states in Context API as my data flow both-ways (I need global state) and to avoid props drilling as well.
I've setup my context.provider in gatsby-ssr.js and gatsby-browser.js like this:
const React = require("react");
const { PhotosContextProvider } = require("./src/contexts/photosContext");
exports.wrapRootElement = ({ element }) => {
return <PhotosContextProvider>{element}</PhotosContextProvider>;
};
I've followed official gatsby documentation for wrapping my root component into context provider.
Gallery.js here I fetch my data and set them into global state:
import { usePhotosContext } from "../contexts/photosContext";
const Test = ({ data }) => {
const { contextData, setContextData } = usePhotosContext();
useEffect(() => {
setContextData(data);
}, [data]);
return (
<div>
<h1>hey from test site</h1>
{contextData.allStrapiCategory.allCategories.map((item) => (
<p>{item.name}</p>
))}
<OtherNestedComponents />
</div>
);
};
export const getData = graphql`
query TestQuery {
allStrapiCategory(sort: { fields: name }) {
allCategories: nodes {
name
}
}
}
`;
export default Test;
NOTE: This is just a test query for simplicity
I've double-checked if I get the data and for typos, and everything works, but the problem occurs when I try to render them out. I get type error undefined. I think it's because it takes a moment to setState so on my first render the contextData array is empty, and after the state is set then the component could render.
Do you have any idea how to work around this or am I missing something? Should I use a different type of query? I'm querying all photos so I don't need to set any variables.
EDIT: I've found a solution for this kinda, basically I check if the data exits and I render my component conditionally.
return testData.length === 0 ? (
<div className="hidden">
<h2>Hey from test</h2>
<p>Nothing to render</p>
</div>
) : (
<div>
<h2>Hey from test</h2>
{testData.allStrapiCategory.allCategories.map((item) => (
<p>{item.name}</p>
))}
</div>
);
However, I find this hacky, and kinda repetitive as I'd have to use this in every component that I use that data at. So I'm still looking for other solutions.
Passing this [page queried] data to root provider doesn't make a sense [neither in gatsby nor in apollo] - data duplication, not required in all pages/etc.
... this data is fetched at build time then no need to check length/loading/etc
... you can render provider in page component to pass data to child components using context (without props drilling).
This is how my app looks like right now:
The search and sort functions are working dynamically, as soon as I type a letter, it finds the match but re-renders all of them.
If I type "hunger", it finds the hunger games films, but it's getting images and rendering when it already has them. Is there any way to make this process just for once so I don't wait for every search, every sorting? I use Redux so data is coming from store, store is getting the data from local json file.
I thought about storing on local storage but I couldn't figure it out. As you can see there is no ComponentDidMount or Hooks.
This is the code of this page:
import React from "react";
import "./MoviesAndSeries.css";
import ListShowItem from "./ListShowItem";
import { getVisibleShows } from "../Redux/Selector";
import { connect } from "react-redux";
import FilterShowItems from "./FilterShowItems";
const Movies: React.FC = (props: any) => {
return (
<div className="movies">
<FilterShowItems />
{props.movies.map((movie: any) => {
return <ListShowItem key={Math.random()} {...movie} />;
})}
</div>
);
};
const mapStateToProps = (state: any) => {
return {
movies: getVisibleShows(state.movies, state.filters),
filters: state.filters,
};
};
export default connect(mapStateToProps)(Movies);
You are using Math.random() as keys. The keys change all the time, and React can't know if the items already exist, so it re-renders all of them:
<ListShowItem key={Math.random()} {...movie} />;
Change the key to something stable, and unique, the movie id (if you have one) for example:
<ListShowItem key={movie.id} {...movie} />;
I have been learning js and then React.js over the last few weeks, following tutorials on Codecademy and then Educative.io (to learn with the new hooks, rather than the class-based approach). In an attempt to apply what I have learned I have been messing around creating a number of common website features as React components on a hello-world project.
Most recently I have been trying to make a search component, which uses the Spotify API to search for a track, but have been running into synchronisation issues which I can't quite figure out how to solve using the js synchronisation tools that I know of. I come from a Java background so am more familiar with mutexes/semaphores/reader-writer locks/monitors so it may be that I am missing something obvious. I have been basing the code on this blog post.
In my implementation, I currently have a SongSearch component, which is passed its initial search text as a property, as well as a callback function which is called when the input value is changed. It also contains searchText as state, which is used to change the value of the input.
import * as React from 'react';
interface Props {
initialSearchText: string,
onSearchTextUpdated: (newSearchText: string) => void;
}
export const SongSearch = (props: Props) => {
const [searchText, setSearchText] = React.useState(props.initialSearchText);
const onChange = (e: React.ChangeEvent<HTMLInputElement>) => {
const newSearchText = e.target.value;
setSearchText(newSearchText);
props.onSearchTextUpdated(newSearchText);
}
return <input value={searchText} onChange={onChange}/>;
};
The results are currently just displayed a list in the SearchResults component, the values of which are passed as an array of songs.
import * as React from 'react';
import { SongInfo } from './index';
interface Props {
songs: SongInfo[]
}
export const SearchResults = (props: Props) => {
return (
<ul>
{props.songs.map((song) => {
return <li key={song.uri}>{song.name}</li>
})}
</ul>
);
}
In the App component, I pass a callback function which sets the state attribute searchText to the new value. This then triggers the effect which calls updateSongs(). If we have an auth token, and the search text isn't empty we return the results of the API call, otherwise we return an empty list of songs. The result is used to update the tracks attribute of the state using setTracks().
I have cutdown the code in App.tsx to only the relevant parts:
import SpotifyWebApi from 'spotify-web-api-js';
import React from "react";
// ... (removed irrelevant code)
async function updateSongs(searchText: string): Promise<SongInfo[]>{
if (spotify.getAccessToken()) {
if (searchText === '') {
console.log('Empty search text.');
return [];
} else {
// if access token has been set
const res = await spotify.searchTracks(searchText, {limit: 10});
const tracks = res.tracks.items.map((trackInfo) => {
return {name: trackInfo.name, uri: trackInfo.uri};
});
console.log(tracks);
return tracks;
}
} else {
console.log('Not sending as access token has not yet');
return [];
}
}
function App() {
// ... (removed irrelevant code)
const initialSearchText = 'Search...';
const [tracks, setTracks] = React.useState([] as SongInfo[]);
const [searchText, setSearchText] = React.useState(initialSearchText);
React.useEffect(() => {
updateSongs(searchText)
.then((newSongs) => setTracks(newSongs))
}, [searchText]);
const content = <SearchResults songs={tracks}/>;
return (
<ThemeProvider theme={theme}>
<div style={{ minHeight: '100vh', display: 'flex', flexDirection: 'column' }}>
<Root config={mui_config}>
<Header
renderMenuIcon={(open: boolean) => (open ? <ChevronLeft /> : <MenuRounded />)}
>
<SongSearch initialSearchText={initialSearchText} onSearchTextUpdated={(newSearchText) => {
console.log(`New Search Text: ${newSearchText}`)
setSearchText(newSearchText);
}}/>
</Header>
<Nav
renderIcon={(collapsed: boolean)=>
collapsed ? <ChevronRight /> : <ChevronLeft />
}
classes={drawerStyles}
>
Nav
</Nav>
<StickyFooter contentBody={content} footerHeight={100} footer={footerContent}/>
</Root>
</div>
</ThemeProvider>
);
}
export default App;
The issue that I am having is that when I type in the name of a long song and then hold down backspace sometimes songs remain displayed in the list even when the search text is empty. From inspection of the console logs in the code I can see that the issue arises because the setTracks() is sometimes called out of order, in particular when deleting 'abcdef' quickly setTracks() the result of updateTracks('a') will be called after the result of updateTracks(''). This makes sense as '' does not require any network traffic, but I have spent hours trying to work out how I can synchronise this in javascript with no avail.
Any help on the matter would be greatly appreciated!
In your case the results are coming back differently because you send multiple events, and the ones that come first - fire a response and then you display it.
My solution would be to use a debounce function on the onChange event of the input field. So that the user will first finish typing and then it should start the search. Although there still might be some problems, if one search has started and the user started typing something else then the first one has finished and the second one has started and finished. In this you might find that cancelling a request helpful. Unfortunately you can't cancel a Promise, so you would have to read about RxJS.
Here's a working example using debounce
P.S.
You might find this conference talk helpful to understand how the event loop is working in JS.
I've been getting started with react-redux and finding it a very interesting way to simplify the front end code for an application using many objects that it acquires from a back end service where the objects need to be updated on the front end in approximately real time.
Using a container class largely automates the watching (which updates the objects in the store when they change). Here's an example:
const MethodListContainer = React.createClass({
render(){
return <MethodList {...this.props} />},
componentDidMount(){
this.fetchAndWatch('/list/method')},
componentWillUnmount(){
if (isFunction(this._unwatch)) this._unwatch()},
fetchAndWatch(oId){
this.props.fetchObject(oId).then((obj) => {
this._unwatch = this.props.watchObject(oId);
return obj})}});
In trying to supply the rest of the application with as simple and clear separation as possible, I tried to supply an alternative 'connect' which would automatically supply an appropriate container thus:
const connect = (mapStateToProps, watchObjectId) => (component) => {
const ContainerComponent = React.createClass({
render(){
return <component {...this.props} />
},
componentDidMount(){
this.fetchAndWatch()},
componentWillUnmount(){
if (isFunction(this._unwatch)) this._unwatch()},
fetchAndWatch(){
this.props.fetchObject(watchObjectId).then((obj) => {
this._unwatch = this.props.watchObject(watchObjectId);
return obj})}
});
return reduxConnect(mapStateToProps, actions)(ContainerComponent)
};
This is then used thus:
module.exports = connect(mapStateToProps, '/list/method')(MethodList)
However, component does not get rendered. The container is rendered except that the component does not get instantiated or rendered. The component renders (and updates) as expected if I don't pass it as a parameter and reference it directly instead.
No errors or warnings are generated.
What am I doing wrong?
This is my workaround rather than an explanation for the error:
In connect_obj.js:
"use strict";
import React from 'react';
import {connect} from 'react-redux';
import {actions} from 'redux/main';
import {gets} from 'redux/main';
import {isFunction, omit} from 'lodash';
/*
A connected wrapper that expects an oId property for an object it can get in the store.
It fetches the object and places it on the 'obj' property for its children (this prop will start as null
because the fetch is async). It also ensures that the object is watched while the children are mounted.
*/
const mapStateToProps = (state, ownProps) => ({obj: gets.getObject(state, ownProps.oId)});
function connectObj(Wrapped){
const HOC = React.createClass({
render(){
return <Wrapped {...this.props} />
},
componentDidMount(){
this.fetchAndWatch()},
componentWillUnmount(){
if (isFunction(this._unwatch)) this._unwatch()},
fetchAndWatch(){
const {fetchObject, watchObject, oId} = this.props;
fetchObject(oId).then((obj) => {
this._unwatch = watchObject(oId);
return obj})}});
return connect(mapStateToProps, actions)(HOC)}
export default connectObj;
Then I can use it anywhere thus:
"use strict";
import React from 'react';
import connectObj from 'redux/connect_obj';
const Method = connectObj(React.createClass({
render(){
const {obj, oId} = this.props;
return (obj) ? <p>{obj.id}: {obj.name}/{obj.function}</p> : <p>Fetching {oId}</p>}}));
So connectObj achieves my goal of creating a project wide replacement for setting up the connect explicitly along with a container component to watch/unwatch the objects. This saves quite a lot of boiler plate and gives us a single place to maintain the setup and connection of the store to the components whose job is just to present the objects that may change over time (through updates from the service).
I still don't understand why my first attempt does not work and this workaround does not support injecting other state props (as all the actions are available there is no need to worry about the dispatches).
Try using a different variable name for the component parameter.
const connect = (mapStateToProps, watchObjectId) => (MyComponent) => {
const ContainerComponent = React.createClass({
render() {
return <MyComponent {...this.props} obj={this.state.obj} />
}
...
fetchAndWatch() {
fetchObject(watchObjectId).then(obj => {
this._unwatch = watchObject(watchObjectId);
this.setState({obj});
})
}
});
...
}
I think the problem might be because the component is in lower case (<component {...this.props} />). JSX treats lowercase elements as DOM element and capitalized as React element.
Edit:
If you need to access the obj data, you'll have to pass it as props to the component. Updated the code snippet