I am trying to make a simple 'Nonogram'/'Picross' game using React to learn UseContext and UseReducer, but am puzzled as to why my top component (App) is not re-rendering when a value it uses changes. Perhaps I am missing something basic, but I've read through documentation and examples online and can't see why it is not re-rendering.
Expectation: User goes on the application, clicks on the squares to change their value (draw a cross by clicking on the squares), and the text underneath the board reads "Congratulations!", as it is based on the value of 'isComplete'
Problem: As above, but 'Keep trying' remains.
I added a button to see the boardState as defined in the UseReducer function, too.
Code is as follows:
App.js
import './App.css';
import { useReducer } from 'react';
import Table from './Table';
import BoardContext from './BoardContext';
import boardReducer from './BoardReducer';
function App() {
//Puzzle layout
const puzzleArray = [
[true, false, true],
[false, true, false],
[true, false, true]
];
//Creating a set of blank arrays to start the game as the userSelection
const generateUserSelection = () => {
const userSelection = [];
puzzleArray.forEach(row => {
let blankRow = [];
row.forEach(square => {
blankRow.push(false)
});
userSelection.push(blankRow);
})
return userSelection;
};
//Initial Context value
const boardInfo = {
puzzleName: "My Puzzle",
puzzleArray: puzzleArray,
userSelection: generateUserSelection(),
isComplete: false
};
const [ boardState, dispatch ] = useReducer(boardReducer, boardInfo)
return (
<BoardContext.Provider value={{board: boardState, dispatch}}>
<div className="App">
<header className="App-header">
<p>
Picross
</p>
<Table />
</header>
<div>
{boardState.isComplete ?
<div>Congratulations!</div>
: <div>Keep trying</div>
}
</div>
<button onClick={() => console.log(boardState)}>boardState</button>
</div>
</BoardContext.Provider>
);
}
export default App;
Table.jsx:
import { useContext, useEffect } from 'react';
import './App.css';
import Square from './Square';
import BoardContext from './BoardContext';
function Table() {
useEffect(() => {console.log('table useEffect')})
const { board } = useContext(BoardContext);
const generateTable = solution => {
const squareLayout = []
for (let i = 0; i < solution.length; i++) {
const squares = []
for (let j = 0; j < solution[i].length; j++) {
squares.push(
<Square
position={{row: i, column: j}}
/>
);
};
squareLayout.push(
<div className="table-row">
{squares}
</div>
);
};
return squareLayout;
};
return (
<div className="grid-container">
{generateTable(board.puzzleArray)}
</div>
);
}
export default Table;
Square.jsx
import { useContext, useState } from 'react';
import './App.css';
import BoardContext from './BoardContext';
function Square(props) {
const { board, dispatch } = useContext(BoardContext)
const [ isSelected, setIsSelected ] = useState(false);
const { position } = props;
const handleToggle = () => {
console.log(board)
board.userSelection[position.row][position.column] = !board.userSelection[position.row][position.column]
dispatch(board);
setIsSelected(!isSelected);
}
return (
<div className={`square ${isSelected ? " selected" : ""}`}
onClick={handleToggle}
>
{position.row}, {position.column}
</div>
);
}
export default Square;
Thanks
Edit: I know for a simple application like this it would be very easy to pass down state through props, but the idea is to practice other hooks, so wanting to avoid it. The ideas I am practicing in this would ideally be extensible to bigger projects in the future.
Edit 2: As requested, here's my BoardReducer.js file:
const boardReducer = (state, updateInfo) => {
let isComplete = false;
if (JSON.stringify(updateInfo.userSelection) === JSON.stringify(state.puzzleArray)) {
isComplete = true;
}
updateInfo.isComplete = isComplete;
return updateInfo;
}
export default boardReducer;
(using JSON.stringify as a cheap way to check matching arrays as it's only a small one for now!)
Issue
You are mutating your state object in a couple places:
const handleToggle = () => {
console.log(board);
board.userSelection[position.row][position.column] = !board.userSelection[position.row][position.column]; // <-- mutation!
dispatch(board);
setIsSelected(!isSelected);
}
And in reducer
const boardReducer = (state, updateInfo) => {
let isComplete = false;
if (JSON.stringify(updateInfo.userSelection) === JSON.stringify(state.puzzleArray)) {
isComplete = true;
}
updateInfo.isComplete = isComplete; // <-- mutation!
return updateInfo; // <-- returning mutated state object
}
Since no new state object is created React doesn't see a state change and doesn't rerender your UI.
Solution
useReducer will typically employ a "redux" pattern where the reducer function consumes the current state and an action to operate on that state, and returns a new state object.
You should dispatch an action that toggles the user selection and checks for a complete board.
Board Reducer
When updating state you should shallow copy any state objects that you are updating into new object references, starting with the entire state object.
const boardReducer = (state, action) => {
if (action.type === "TOGGLE") {
const { position } = action;
const nextState = {
...state,
userSelection: state.userSelection.map((rowEl, row) =>
row === position.row
? rowEl.map((colEl, col) =>
col === position.column ? !colEl : colEl
)
: rowEl
)
};
nextState.isComplete =
JSON.stringify(nextState.userSelection) ===
JSON.stringify(state.puzzleArray);
return nextState;
}
return state;
};
Create an action creator, which is really just a function that returns an action object.
const togglePosition = position => ({
type: "TOGGLE",
position
});
Then the handleToggle should consume/pass the row and column position in a dispatched action.
const handleToggle = () => dispatch(togglePosition(position));
Simple Demo
Demo Code:
const puzzleArray = [
[true, false, true],
[false, true, false],
[true, false, true]
];
const userSelection = Array(3).fill(Array(3).fill(false));
const togglePosition = (row, column) => ({
type: "TOGGLE",
position: { row, column }
});
const boardReducer = (state, action) => {
if (action.type === "TOGGLE") {
const { position } = action;
const nextState = {
...state,
userSelection: state.userSelection.map((rowEl, row) =>
row === position.row
? rowEl.map((colEl, col) =>
col === position.column ? !colEl : colEl
)
: rowEl
)
};
nextState.isComplete =
JSON.stringify(nextState.userSelection) ===
JSON.stringify(state.puzzleArray);
return nextState;
}
return state;
};
export default function App() {
const [boardState, dispatch] = React.useReducer(boardReducer, {
puzzleArray,
userSelection,
isComplete: false
});
const handleClick = (row, column) => () =>
dispatch(togglePosition(row, column));
return (
<div className="App">
<h1>Hello CodeSandbox</h1>
<h2>Start editing to see some magic happen!</h2>
<div>{boardState.isComplete ? "Congratulations!" : "Keep Trying"}</div>
<div>
{boardState.userSelection.map((row, r) => (
<div key={r}>
{row.map((col, c) => (
<span
key={c}
className={classnames("square", { active: col })}
onClick={handleClick(r, c)}
/>
))}
</div>
))}
</div>
</div>
);
}
Related
I have a componenet that wraps its children and slides them in and out based on the stage prop, which represents the active child's index.
As this uses a .map() to wrap each child in a div for styling, I need to give each child a key prop. I want to assign a random key as the children could be anything.
I thought I could just do this
key={`pageSlide-${uuid()}`}
but it causes an infinite loop/React to freeze and I can't figure out why
I have tried
Mapping the children before render and adding a uuid key there, calling it via key={child.uuid}
Creating an array of uuids and assigning them via key={uuids[i]}
Using a custom hook to store the children in a state and assign a uuid prop there
All result in the same issue
Currently I'm just using the child's index as a key key={pageSlide-${i}} which works but is not best practice and I want to learn why this is happening.
I can also assign the key directly to the child in the parent component and then use child.key but this kinda defeats the point of generating the key
(uuid is a function from react-uuid, but the same issue happens with any function including Math.random())
Here is the full component:
import {
Children,
useCallback,
useEffect,
useMemo,
useRef,
useState,
} from "react";
import PropTypes from "prop-types";
import uuid from "react-uuid";
import ProgressBarWithTicks from "./ProgressBarWithTicks";
import { childrenPropType } from "../../../propTypes/childrenPropTypes";
const calculateTranslateX = (i = 0, stage = 0) => {
let translateX = stage === i ? 0 : 100;
if (i < stage) {
translateX = -100;
}
return translateX;
};
const ComponentSlider = ({ stage, children, stageCounter }) => {
const childComponents = Children.toArray(children);
const containerRef = useRef(null);
const [lastResize, setLastResize] = useState(null);
const [currentMaxHeight, setCurrentMaxHeight] = useState(
containerRef.current?.childNodes?.[stage]?.clientHeight
);
const updateMaxHeight = useCallback(
(scrollToTop = true) => {
if (scrollToTop) {
window.scrollTo(0, 0);
}
setCurrentMaxHeight(
Math.max(
containerRef.current?.childNodes?.[stage]?.clientHeight,
window.innerHeight -
(containerRef?.current?.offsetTop || 0) -
48
)
);
},
[stage]
);
useEffect(updateMaxHeight, [stage, updateMaxHeight]);
useEffect(() => updateMaxHeight(false), [lastResize, updateMaxHeight]);
const resizeListener = useMemo(
() => new MutationObserver(() => setLastResize(Date.now())),
[]
);
useEffect(() => {
if (containerRef.current) {
resizeListener.observe(containerRef.current, {
childList: true,
subtree: true,
});
}
}, [resizeListener]);
return (
<div className="w-100">
{stageCounter && (
<ProgressBarWithTicks
currentStage={stage}
stages={childComponents.length}
/>
)}
<div
className="position-relative divSlider align-items-start"
ref={containerRef}
style={{
maxHeight: currentMaxHeight || null,
}}>
{Children.map(childComponents, (child, i) => (
<div
key={`pageSlide-${uuid()}`}
className={`w-100 ${
stage === i ? "opacity-100" : "opacity-0"
} justify-content-center d-flex`}
style={{
zIndex: childComponents.length - i,
transform: `translateX(${calculateTranslateX(
i,
stage
)}%)`,
pointerEvents: stage === i ? null : "none",
cursor: stage === i ? null : "none",
}}>
{child}
</div>
))}
</div>
</div>
);
};
ComponentSlider.propTypes = {
children: childrenPropType.isRequired,
stage: PropTypes.number,
stageCounter: PropTypes.bool,
};
ComponentSlider.defaultProps = {
stage: 0,
stageCounter: false,
};
export default ComponentSlider;
It is only called in this component (twice, happens in both instances)
import { useEffect, useReducer, useState } from "react";
import { useParams } from "react-router-dom";
import {
FaCalendarCheck,
FaCalendarPlus,
FaHandHoldingHeart,
} from "react-icons/fa";
import { IoIosCart } from "react-icons/io";
import { mockMatches } from "../../../templates/mockData";
import { initialSwapFormState } from "../../../templates/initalStates";
import swapReducer from "../../../reducers/swapReducer";
import useFetch from "../../../hooks/useFetch";
import useValidateFields from "../../../hooks/useValidateFields";
import IconWrap from "../../common/IconWrap";
import ComponentSlider from "../../common/transitions/ComponentSlider";
import ConfirmNewSwap from "./ConfirmSwap";
import SwapFormWrapper from "./SwapFormWrapper";
import MatchSwap from "../Matches/MatchSwap";
import SwapOffers from "./SwapOffers";
import CreateNewSwap from "./CreateNewSwap";
import smallNumberToWord from "../../../functions/utils/numberToWord";
import ComponentFader from "../../common/transitions/ComponentFader";
const formStageHeaders = [
"What shift do you want to swap?",
"What shifts can you do instead?",
"Pick a matching shift",
"Good to go!",
];
const NewSwap = () => {
const { swapIdParam } = useParams();
const [formStage, setFormStage] = useState(0);
const [swapId, setSwapId] = useState(swapIdParam || null);
const [newSwap, dispatchNewSwap] = useReducer(swapReducer, {
...initialSwapFormState,
});
const [matches, setMatches] = useState(mockMatches);
const [selectedMatch, setSelectedMatch] = useState(null);
const [validateHook, newSwapValidationErrors] = useValidateFields(newSwap);
const fetchHook = useFetch();
const setStage = (stageIndex) => {
if (!swapId && stageIndex > 1) {
setSwapId(Math.round(Math.random() * 100));
}
if (stageIndex === "reset") {
setSwapId(null);
dispatchNewSwap({ type: "reset" });
}
setFormStage(stageIndex === "reset" ? 0 : stageIndex);
};
const saveMatch = async () => {
const matchResponse = await fetchHook({
type: "addSwap",
options: { body: newSwap },
});
if (matchResponse.success) {
setStage(3);
} else {
setMatches([]);
dispatchNewSwap({ type: "setSwapMatch" });
setStage(1);
}
};
useEffect(() => {
// set matchId of new selected swap
dispatchNewSwap({ type: "setSwapMatch", payload: selectedMatch });
}, [selectedMatch]);
return (
<div>
<div className="my-3">
<div className="d-flex justify-content-center w-100 my-3">
<ComponentSlider stage={formStage}>
<IconWrap colour="primary">
<FaCalendarPlus />
</IconWrap>
<IconWrap colour="danger">
<FaHandHoldingHeart />
</IconWrap>
<IconWrap colour="warning">
<IoIosCart />
</IconWrap>
<IconWrap colour="success">
<FaCalendarCheck />
</IconWrap>
</ComponentSlider>
</div>
<ComponentFader stage={formStage}>
{formStageHeaders.map((x) => (
<h3
key={`stageHeading-${x.id}`}
className="text-center my-3">
{x}
</h3>
))}
</ComponentFader>
</div>
<div className="mx-auto" style={{ maxWidth: "400px" }}>
<ComponentSlider stage={formStage} stageCounter>
<SwapFormWrapper heading="Shift details">
<CreateNewSwap
setSwapId={setSwapId}
newSwap={newSwap}
newSwapValidationErrors={newSwapValidationErrors}
dispatchNewSwap={dispatchNewSwap}
validateFunction={validateHook}
setStage={setStage}
/>
</SwapFormWrapper>
<SwapFormWrapper heading="Swap in return offers">
<p>
You can add up to{" "}
{smallNumberToWord(5).toLowerCase()} offers, and
must have at least one
</p>
<SwapOffers
swapId={swapId}
setStage={setStage}
newSwap={newSwap}
dispatchNewSwap={dispatchNewSwap}
setMatches={setMatches}
/>
</SwapFormWrapper>
<SwapFormWrapper>
<MatchSwap
swapId={swapId}
setStage={setStage}
matches={matches}
selectedMatch={selectedMatch}
setSelectedMatch={setSelectedMatch}
dispatchNewSwap={dispatchNewSwap}
saveMatch={saveMatch}
/>
</SwapFormWrapper>
<SwapFormWrapper>
<ConfirmNewSwap
swapId={swapId}
setStage={setStage}
selectedSwap={selectedMatch}
newSwap={newSwap}
/>
</SwapFormWrapper>
</ComponentSlider>
</div>
</div>
);
};
NewSwap.propTypes = {};
export default NewSwap;
One solution
#Nick Parsons has pointed out I don't even need a key if using React.Children.map(), so this is a non issue
I'd still really like to understand what was causing this problem, aas far as I can tell updateMaxHeight is involved, but I can't quite see the chain that leads to an constant re-rendering
Interstingly if I use useMemo for an array of uuids it works
const uuids = useMemo(
() => Array.from({ length: childComponents.length }).map(() => uuid()),
[childComponents.length]
);
/*...*/
key={uuids[i]}
Whilst I am doing cart in react, I have no idea why I keep getting NaN value - only from a specific object data.
When I have the following data list:
#1 ItemsList.js
export const ItemsList = [
{
id: 1,
name: "VA-11 Hall-A: Cyberpunk Bartender Action",
price: 110000,
image: cover1,
link: "https://store.steampowered.com/app/447530/VA11_HallA_Cyberpunk_Bartender_Action/?l=koreana",
},
...
{
id: 6,
name: "Limbus Company",
price: 110000,
image: cover6,
link: "https://limbuscompany.com/",
},
];
And the following code, please look at the comment line.
#2 Goods.jsx
import React, { useContext } from "react";
import "./Goods.css";
import { DataContext } from "../../components/context/DataContext";
export const Goods = (props) => {
const { id, name, price, image, link } = props.shopItemProps;
const { cartItems, addItemToCart, removeItemFromCart } =
useContext(DataContext);
const cartItemStored = cartItems[id];
return (
<div className="goods">
<div className="goods-id">{id}</div>
<img src={image} alt="thumbnail_image" className="goods-image" />
<div className="goods-name">{name}</div>
<div className="goods-price">${price}</div>
<button>
<a href={link} className="goods-link">
Official Store Page
</a>
</button>
<div className="cart-button">
<button onClick={() => removeItemFromCart(id)}>-</button>
// ★Maybe here? but why do I get NaN only for id:6? Others work well.
{cartItemStored > -1 && <> ({cartItemStored}) </>}
<button onClick={() => addItemToCart(id)}>+</button>
</div>
</div>
);
};
What should I do to solve NaN? There seems to be no way to make that value as int in this case. Or do you see any problem from the above code block?
Edited
Sorry for confusing you. Here are the additional code related.
#3. DataContext.js (where cartItems state exists)
import React, { createContext, useState } from "react";
import { ItemsList } from "../ItemsList";
export const DataContext = createContext(null);
const getDefaultCart = () => {
let cart = {};
for (let i = 1; i < ItemsList.length; i++) {
cart[i] = 0;
}
return cart;
};
export const DataContextProvider = (props) => {
const [cartItems, setCartItems] = useState(getDefaultCart);
const checkoutTotalSum = () => {
let totalAmount = 0;
for (const item in cartItems) {
if (cartItems[item] > 0) {
let itemInfo = ItemsList.find((product) => product.id === Number(item));
totalAmount += cartItems[item] * itemInfo.price;
}
}
return totalAmount;
};
const addItemToCart = (itemId) => {
setCartItems((prev) => ({ ...prev, [itemId]: prev[itemId] + 1 }));
};
const removeItemFromCart = (itemId) => {
setCartItems((prev) => ({ ...prev, [itemId]: prev[itemId] - 1 }));
};
const updateCartItemCount = (newAmount, itemId) => {
setCartItems((prev) => ({ ...prev, [itemId]: newAmount }));
};
const contextValue = {
cartItems,
addItemToCart,
removeItemFromCart,
updateCartItemCount,
checkoutTotalSum,
};
// console.log(cartItems);
return (
<DataContext.Provider value={contextValue}>
{props.children}
</DataContext.Provider>
);
};
The issue is in the function you are using to set the initial value of cartItems, more specifically, in the for loop. This line is the culprit: i < ItemsList.length, when in your case, it should be i <= ItemsList.length. Why? because you are not including the last element of ItemsList on the cart object (you are initializing the i counter with 1 and ItemsList's length is 6).
So, when you call addItemToCart:
const addItemToCart = (itemId) => {
setCartItems((prev) => ({ ...prev, [itemId]: prev[itemId] + 1 }));
};
And try to update the value corresponding to the last element of ItemsList which is 6 in cartItems, you're getting: '6': undefined + 1 because again, you did skip the last element in the for loop. This results in NaN.
You also have the option of initializing i with 0 and preserve this line: i < ItemsList.length, or:
for (let i = 1; i < ItemsList.length + 1; i++) {
...
}
I am working on trying to get this counter for pintsLeft to work. This is my first project with React and I feel that I am either not passing the property of the array correctly or my function code is not set correctly.
^^^^KegDetail.js^^^^
import React from "react";
import PropTypes from "prop-types";
function KegDetail(props){
const { keg, onClickingDelete} = props
return (
<React.Fragment>
<hr/>
<h2>{keg.name} Made By {keg.brewery}</h2>
<p>abv {keg.abv}</p>
<h3>price {keg.price}</h3>
<p>{keg.pintsLeft} total pints left</p> {/* Make this a percentage */}
<hr/>
<button onClick={ props.onClickingEdit }>Update Keg</button>
<button onClick={()=> onClickingDelete(keg.id) }>Delete Keg</button>
<button onClick={()=> this.onSellingPint()}>Sell A Pint!</button>
</React.Fragment>
);
}
KegDetail.propTypes = {
keg: PropTypes.object,
onClickingDelete: PropTypes.func,
onClickingEdit:PropTypes.func,
onSellingPint:PropTypes.func
}
export default KegDetail;
That was my KegDetail.js
import React, {useState} from "react";
import NewKegForm from "./NewKegForm";
import DraftList from "./DraftList";
import KegDetail from "./KegDetail";
import EditKegForm from "./EditKegForm";
class DraftControl extends React.Component {
constructor(props){
super(props);
this.state = {
kegFormVisibleOnPage: false,
fullDraftList: [],
selectedKeg: null,
editing: false,
pints: 127,
};
this.handleClick = this.handleClick.bind(this);
this.handleSellingPint = this.handleSellingPint.bind(this);
}
handleClick = () => {
if (this.state.selectedKeg != null){
this.setState({
kegFormVisibleOnPage: false,
selectedKeg: null,
editing: false
});
} else {
this.setState(prevState => ({
kegFormVisibleOnPage: !prevState.kegFormVisibleOnPage,
}));
}
}
handleSellingPint = () => {
this.setState({
pints:this.state.pints-1
})
};
render() {
let currentlyVisibleState = null;
let buttonText = null;
if (this.state.editing){
currentlyVisibleState = <EditKegForm keg = {this.state.selectedKeg} onEditKeg = {this.handleEditingKegInDraftList} />
buttonText = "Return to the Draft List"
}
else if (this.state.selectedKeg != null){
currentlyVisibleState = <KegDetail keg = {this.state.selectedKeg} onClickingDelete = {this.handleDeletingKeg}
onClickingEdit = {this.handleEditClick} onSellingPint = {this.handleSellingPint}/>
buttonText = "Return to the Keg List"
My DraftControl.js code
I don't know what I am doing wrong. I cant get the keg.pintsLeft to pass a number when I console.log, So I may be targeting it incorrectly.
Thanks again!
Try it like this:
handleSellingPint = () => {
this.setState(prevState => {
return {
pints: prevState.pints-1
}
})
};
edit
Also, you invoke the onSellingPint() in a wrong way.
It's not a class component, so React doesn't know what does this refer to.
The function itself is passed in as a prop, so you should reference it like this: <button onClick={() => props.onSellingPint() />
handleSellingPint = (id) => {
const clonedArray = [...this.state.fullDraftList]
for (let i = 0; i < this.state.fullDraftList.length; i++){
if (clonedArray[i].id === id){
clonedArray[i].pintsLeft -= 1
}
}
this.setState({
fullDraftList: clone
});
}
Is what I came up with.
Since you are alteriting a state within an array, you need to clone the array and work on that array, not the "real" one.
Thanks for all your help!
I've created a simple todo list to learn react and i'm trying to add some additional features. At the moment i'm trying to add buttons that toggle the list of items, so it either shows all the tasks or just those that are completed.
I've written a function to change the state of my visabilityFilter so I can later use this to toggle the items in the list, but it isn't behaving how it should be.
I console log the visabilityFilter variable but it always shows the wrong state before changing to the correct state. e.g. the 'show all' button will console log 'show completed' then if you press it again it will console log 'show all'
App.js
import React, { Component } from 'react';
import './App.css';
import TodoList from './components/TodoList.js'
import VisabilityFilter from './components/VisabilityFilter.js'
export const SHOW_ALL = 'show_all'
export const SHOW_COMPLETED = 'show_completed'
class App extends Component {
constructor (props) {
super(props)
this.state = {
inputValues: {
'newTodo': ''
},
todos: [
{
task: 'My First Todo',
completed: false
}
],
visabilityFilter: SHOW_ALL
}
this.addTodo = this.addTodo.bind(this)
this.handleInputChange = this.handleInputChange.bind(this)
this.handleKeyUp = this.handleKeyUp.bind(this)
this.toggleCompleted = this.toggleCompleted.bind(this)
this.removeTodo = this.removeTodo.bind(this)
this.checkCompleted = this.checkCompleted.bind(this)
this.setVisabilityFilter = this.setVisabilityFilter.bind(this)
}
handleInputChange (e) {
const { inputValues } = this.state
const { id, value } = e.target
this.setState({
inputValues: {
...inputValues,
[id]: value
}
})
}
handleKeyUp (e) {
var code = e.key
if(code === 'Enter') {
this.addTodo(e);
}
}
toggleCompleted (e, index) {
const { todos } = this.state
todos[index].completed = !todos[index].completed
todos.sort((a, b) => b.completed - a.completed)
this.setState({ todos })
}
removeTodo (e, index) {
const { todos } = this.state
this.setState ({ todos: todos.filter((todo, i) => i !== index) })
}
addTodo (e) {
const { todos, inputValues } = this.state
const { dataset } = e.target
if (inputValues[dataset.for] === '') return
const newTodo = { task: inputValues[dataset.for], completed: false }
todos.push(newTodo)
this.setState({
todos,
inputValues: { ...inputValues, [dataset.for]: '' }
})
}
checkCompleted (e, index) {
const { todos } = this.state
return { todos } && todos[index].completed
}
setVisabilityFilter (e) {
const { visabilityFilter } = this.state
const { dataset } = e.target
this.setState({
visabilityFilter: dataset.for
})
console.log ({ visabilityFilter })
}
render() {
const { todos, inputValues, visabilityFilter } = this.state
return (
<div className="App">
<TodoList
todos={todos}
inputValues={inputValues}
addTodo={this.addTodo}
handleInputChange={this.handleInputChange}
removeTodo={this.removeTodo}
toggleCompleted={this.toggleCompleted}
handleKeyUp={this.handleKeyUp}
checkCompleted={this.checkCompleted}
/>
<VisabilityFilter setVisabilityFilter={this.setVisabilityFilter} />
</div>
);
}
}
export default App;
VisabilityFilter.js
import React from 'react'
import { func } from 'prop-types'
import { SHOW_ALL, SHOW_COMPLETED } from '../App'
const VisabilityFilter = props => {
return (
<div>
<button data-for={SHOW_COMPLETED} onClick={ props.setVisabilityFilter } >
Show Completed Tasks
</button>
<button data-for={SHOW_ALL} onClick={ props.setVisabilityFilter }>
Show All Tasks
</button>
</div>
)
}
VisabilityFilter.propTypes = {
setVisabilityFilter: func.isRequired
}
export default VisabilityFilter
setState() is async (React docs), so the state changes won't be applied immediately. If you want to log out the new state,setState() takes in a function as the second argument and performs that function when the state is updated. So:
this.setState({
abc: xyz
},
() => console.log(this.state.abc),
)
Or you can also use componentDidUpdate(), which is recommended
In the functional components, you can use useEffect to track changes in state.
useEffect(() => {
console.log(someState);
},[someState);
I am making a React App for Ping Pong Tournament. Code below.
import React, { Fragment, Component } from "react";
import Button from "./Button";
const playerStylingTrue = {
backgroundColor: "#26C281"
};
class Matches extends Component {
constructor(props) {
super(props);
this.state = {
numOfRounds: "",
numberOfPlayers: this.props.numberOfPlayers,
player1Clicked: false,
player2Clicked: false,
winners: []
}
this.onClickWinnerP1 = this.onClickWinnerP1.bind(this);
this.onClickWinnerP2 = this.onClickWinnerP2.bind(this);
}
numberOfRounds() {
const { numberOfPlayers } = this.state;
const numOfRounds = Math.ceil((Math.log(numberOfPlayers)) /
(Math.log(2)));
this.setState = ({
numOfRounds: numOfRounds
})
};
onClickWinnerP1(player1) {
let player1String = player1.toString()
let { winners } = this.state;
// let findWinner = winners.find(o => o.player1String === player1);
//winners.includes(findWinner) ? null :
this.setState({
player1Clicked: !this.state.player1Clicked,
player2Clicked: this.state.player1Clicked,
winners: [{...winners, player1String, winner:true}]
})
};
onClickWinnerP2(player2) {
let player2String = player2.toString()
let { winners } = this.state;
this.setState({
player2Clicked: !this.state.player2Clicked,
player1Clicked: this.state.player2Clicked,
winners: winners.includes(player2String) ? [...winners] :
[{...winners, player2String, winner:true}]
})
};
render() {
const { pairs } = this.props;
const { winners } = this.state;
console.log(winners)
return (
<Fragment>
<Button
onClick={this.props.onClick}
className={"btn btn-success"}
buttonText={"Create Random Matches 🏓"}
/>
{pairs.map((pair, i) => {
let player1 = [...pair];
let player2 = player1.splice(0, Math.ceil(player1.length /
2));
return (
<div key={i} className="fixture-div">
<ul className="list-unstyled fixture-list">
<li
style={ this.state.winners.includes(player1) ? playerStylingTrue : null}
onClick={() => this.onClickWinnerP1(player1)}
className="hvr-grow fixture">
{player1}
</li>
<span>vs</span>
<li
style={this.state.winners.includes(player2) ? playerStylingTrue : null}
onClick={() => this.onClickWinnerP2(player2)}
className="hvr-grow fixture">
{player2}
</li>
</ul>
</div>
)
})
}
{/* <TwoRounds pairs={pairs}/> */}
</Fragment>
);
}
}
export default Matches;
Currently the onClickWinnerP1 successfully add an object to the state, containing the correct details. However if I click twice or use onClickWinnerP2, is also adds an object to the state, but nested within the object that is already there. And so on, so on. Just keeps nesting.
Any help would be greatly appreciated!
The way you are doing setState in noOfRounds function isn't correct. Instead you should do like below
this.setState({
numOfRounds: numOfRounds
})
Regarding your issue, do something like below in onClickWinnerP1 function to push objects into an array
this.setState(prevState => ({
player1Clicked: !this.state.player1Clicked,
player2Clicked: this.state.player1Clicked,
winners: [...prevState.winners, {player1String, winner:true}]
}))
AND in onClickWinnerP2 function do something like below to push objects into an array
this.setState(prevState => ({
player2Clicked: !this.state.player2Clicked,
player1Clicked: this.state.player2Clicked,
winners: prevState.winners.includes(player2String) ? [...prevState.winners] :
[...prevState.winners, {player2String, winner:true}]
}))