I am using React's Context API to share data that most of my components need.
The Context is initially defined, but shortly receives data from the Firebase database (please see IdeaContext.tsx). I define the context in a functional component and the display component, which returns a small card based on the information received.
However, the component doesn't render when I start the development server with Yarn. Instead, in order to get it to render, I have to write console.log('something') inside the display component and then it suddenly re-renders. However, when I refresh the server, it again doesn't render.
How can I make my component render immediately (or at least after the context updates with the data from the database?)
Code:
Context Definition:
import React, { createContext, useEffect, useState } from "react";
import { IdeaContextType, Idea } from "../t";
import {ideasRef} from './firebase'
function getIdeas() {
var arr: Array<Idea> = [];
ideasRef.on('value', (snapshot) => {
let items = snapshot.val()
snapshot.forEach( (idea) => {
const obj = idea.val()
arr.push({
title: obj.title,
description: obj.description,
keyID: obj.keyID
})
console.log(arr)
})
})
return arr
}
const IdeaContextDefaultValues: IdeaContextType = {
ideas: [],
setIdeas: () => {},
};
const IdeaContext = createContext<IdeaContextType>(IdeaContextDefaultValues)
const IdeaContextProvider: React.FC = ({ children }) => {
const [ideas, setIdeas] = useState<Array<Idea>>(
IdeaContextDefaultValues.ideas);
useEffect( ()=> {
console.log('getting info')
setIdeas(getIdeas())
}, [])
useEffect( () => {
console.log('idea change: ', ideas)
}, [ideas])
return (
<IdeaContext.Provider value={{ ideas, setIdeas }}>
{children}
</IdeaContext.Provider>
);
};
Displayer and Card Component
import React, { FC, ReactElement, useContext } from "react";
import IdeaCreator from "./IdeaCreator";
import { IdeaContext } from "./IdeaContext";
import { Idea } from "../t";
import { Link } from "react-router-dom";
const IdeaPost:React.FC<Idea> = ({title, keyID, description}):ReactElement => {
console.log('Received',title,description,keyID)
return (
<div className="max-w-sm rounded overflow-hidden shadow-lg">
<img
className="w-full"
src="#"
alt="Oopsy daisy"
/>
<div className="px-6 py-4">
<div className="font-bold text-xl mb-2"> <Link to={"ideas/" + keyID} key= {keyID}> {title}</Link> </div>
<p className="text-gray-700 text-base">{description}</p>
</div>
</div>
);
};
const IdeaDisplay:FC<any> = (props:any):ReactElement => {
const { ideas, setIdeas } = useContext(IdeaContext)
console.log('Ideas in display: ', ideas)
console.log('test') //This is what I comment and uncommend to get it to show
return (
<div className="flex flex-wrap ">
{ideas.map((idea) => {
console.log(idea)
console.log('Sending',idea.title,idea.description,idea.keyID)
console.log(typeof idea.keyID)
return (
<IdeaPost
title={idea.title}
description={idea.description}
keyID = {idea.keyID}
key = {idea.keyID * 100}
/>
);
})}
</div>
);
};
export default IdeaDisplay;
Solution Code:
import React, { createContext, useEffect, useState } from "react";
import { IdeaContextType, Idea } from "../t";
import {ideasRef} from './firebase'
async function getIdeas() {
var arr: Array<Idea> = [];
const snapshot = await ideasRef.once("value");
snapshot.forEach((idea) => {
const obj = idea.val();
arr.push({
title: obj.title,
description: obj.description,
keyID: obj.keyID,
});
console.log(arr);
});
return arr
}
const IdeaContextDefaultValues: IdeaContextType = {
ideas: [],
setIdeas: () => {},
};
const IdeaContext = createContext<IdeaContextType>(IdeaContextDefaultValues)
const IdeaContextProvider: React.FC = ({ children }) => {
const [ideas, setIdeas] = useState<Array<Idea>>(
IdeaContextDefaultValues.ideas);
useEffect(() => {
console.log("getting info");
const setup = async () => {
const ideas = await getIdeas();
setIdeas(ideas);
};
setup()
}, []);
useEffect( () => {
console.log('idea change: ', ideas)
const updateDatabase = async () => {
await ideasRef.update(ideas)
console.log('updated database')
}
updateDatabase()
}, [ideas])
return (
<IdeaContext.Provider value={{ ideas, setIdeas }}>
{children}
</IdeaContext.Provider>
);
};
export {IdeaContext, IdeaContextProvider}
First of all you would need to use once and not on if you want to get the data only once. If you want to use a realtime listener you could send the setIdeas to your function. Also try to be carefull with async/away calls to the Firebase sdk. Your code could look like this:
import React, { createContext, useEffect, useState } from "react";
import { IdeaContextType, Idea } from "../t";
import { ideasRef } from "./firebase";
async function getIdeas() {
var arr: Array<Idea> = [];
const snapshot = await ideasRef.once("value");
let items = snapshot.val();
snapshot.forEach((idea) => {
const obj = idea.val();
arr.push({
title: obj.title,
description: obj.description,
keyID: obj.keyID,
});
console.log(arr);
});
return arr;
}
const IdeaContextDefaultValues: IdeaContextType = {
ideas: [],
setIdeas: () => {},
};
const IdeaContext = createContext < IdeaContextType > IdeaContextDefaultValues;
const IdeaContextProvider: React.FC = ({ children }) => {
const [ideas, setIdeas] =
useState < Array < Idea >> IdeaContextDefaultValues.ideas;
useEffect(() => {
console.log("getting info");
const getData = async () => {
const ideas = await getIdeas();
setIdeas(ideas);
};
}, []);
useEffect(() => {
console.log("idea change: ", ideas);
}, [ideas]);
return (
<IdeaContext.Provider value={{ ideas, setIdeas }}>
{children}
</IdeaContext.Provider>
);
};
Related
I have a NextJS application that is using the ShopifyBuy SDK. I have been successfully able to implement a solution where I am able to fetch the products from Store and display them to the User. The user is also able to go to a product page and add the product to the cart.
However, when the user refreshes the page, the cart is reset, and the data does not persist. The code is below:
context/cart.js:
import { createContext, useContext, useEffect, useReducer } from "react";
import client from "../lib/client";
import Cookies from "js-cookie";
const CartStateContext = createContext();
const CartDispatchContext = createContext();
const SET_CART = "SET_CART";
const initalState = {
lineItems: [],
totalPrice: 0,
webUrl: "",
id: "",
};
const reducer = (state, action) => {
switch (action.type) {
case SET_CART:
return { ...state, ...action.payload };
default:
throw new Error(`Unknown action: ${action.type}`);
}
};
export const CartProvider = ({ children }) => {
const savedState = Cookies.get("cartState");
const [state, dispatch] = useReducer(reducer, savedState || initalState);
useEffect(() => {
Cookies.set("cartState", state, { expires: 7 });
}, [state]);
useEffect(() => {
getCart();
}, []);
const setCart = (payload) => dispatch({ type: SET_CART, payload });
const getCart = async () => {
try {
const cart = await client.checkout.create();
setCart(cart);
} catch (err) {
console.log(err);
}
};
return (
<CartDispatchContext.Provider value={{ setCart }}>
<CartStateContext.Provider value={{ state }}>
{children}
</CartStateContext.Provider>
</CartDispatchContext.Provider>
);
};
export const useCartState = () => useContext(CartStateContext);
export const useCartDispatch = () => useContext(CartDispatchContext);
products/[handle].tsx:
import React, { useState, useEffect } from "react";
import client from "../../lib/client";
import { useCartDispatch, useCartState } from "../../context/cart";
import Link from "next/link";
import cookie from "js-cookie";
export const getStaticPaths = async () => {
const res = await client.product.fetchAll();
const paths = res.map((product: any) => {
return {
params: { handle: product.handle.toString() },
};
});
return {
paths,
fallback: false,
};
};
export const getStaticProps = async (context: any) => {
const handle = context.params.handle;
const res = await client.product.fetchByHandle(handle);
const product = JSON.stringify(res);
return {
props: {
product,
},
};
};
function Product({ product }: any) {
const { state } = useCartState();
const { setCart } = useCartDispatch();
const addToCart = async () => {
const checkoutId = state.id;
const lineItemsToAdd = [
{
variantId: product.variants[0].id,
quantity: 1,
},
];
const res = await client.checkout.addLineItems(checkoutId, lineItemsToAdd);
setCart(res);
};
product = JSON.parse(product);
return (
<div>
<div className=" flex-col text-2xl font-bold m-8 flex items-center justify-center ">
<h1>{product.title}</h1>
<button onClick={addToCart}>Add to Cart</button>
<Link href="/cart">Checkout</Link>
</div>
</div>
);
}
export default Product;
pages/cart/index.tsx:
import React, { useEffect } from "react";
import { useCartState, useCartDispatch } from "../../context/cart";
import client from "../../lib/client";
function Cart() {
const { state } = useCartState();
return (
<div>
<h1>Cart</h1>
{state.lineItems &&
state.lineItems.map((item: any) => {
return (
<div key={item.id}>
<h2>{item.title}</h2>
<p>{item.variant.title}</p>
<p>{item.quantity}</p>
</div>
);
})}
</div>
);
}
export default Cart;
I have tried using a library called js-cookie and also localStorage. I'm not sure where the problem lies or if the solutions that I've tried are wrong.
P.S.: I'm fairly new to NextJS and Typescript so go easy on the syntax. This code is for a personal project. Thanks in advance!
Answering this because I ended up coming up with a solution that works for me, at least.
Here it is:
const getCart = async () => {
try {
const checkoutId = Cookies.get("checkoutId");
let cart;
if (checkoutId) {
cart = await client.checkout.fetch(checkoutId);
} else {
cart = await client.checkout.create();
Cookies.set("checkoutId", cart.id);
}
setCart(cart);
} catch (err) {
console.log(err);
}
};
From my understanding, what this does is the following:
Check the cookies to see if one exists called "checkoutId"
If it exists, fetch the cart using that checkoutId
Otherwise, create a new cart and create a cookie using the cart.id that is returned in the response
Then, inside my individual Product page ([handle].tsx), I'm doing the following:
const addToCart = async () => {
const checkoutId = state.id;
const lineItemsToAdd = [
{
variantId: product.variants[0].id,
quantity: 1,
},
];
const res = await client.checkout.addLineItems(checkoutId, lineItemsToAdd);
console.log(res);
if (cookie.get("checkoutId") === undefined) {
cookie.set("checkoutId", res.id);
}
setCart(res);
};
Using cookies to store your object cart, as far as I know, is not a good idea. You could use localStorage, like so:
import { createContext, useContext, useEffect, useReducer } from "react";
import client from "../lib/client";
const CartStateContext = createContext();
const CartDispatchContext = createContext();
const SET_CART = "SET_CART";
const initalState =
typeof localStorage !== "undefined" && localStorage.getItem("cartState")
? JSON.parse(localStorage.getItem("cartState"))
: {
lineItems: [],
totalPrice: 0,
webUrl: "",
id: "",
};
const reducer = (state, action) => {
switch (action.type) {
case SET_CART:
return { ...state, ...action.payload };
default:
throw new Error(`Unknown action: ${action.type}`);
}
};
export const CartProvider = ({ children }) => {
const [state, dispatch] = useReducer(reducer, initalState);
useEffect(() => {
localStorage.set("cartState", JSON.stringify(state));
}, [state]);
useEffect(() => {
getCart();
}, []);
const setCart = (payload) => dispatch({ type: SET_CART, payload });
const getCart = async () => {
try {
const cart = await client.checkout.create();
setCart(cart);
} catch (err) {
console.log(err);
}
};
return (
<CartDispatchContext.Provider value={{ setCart }}>
<CartStateContext.Provider value={{ state }}>{children}</CartStateContext.Provider>
</CartDispatchContext.Provider>
);
};
export const useCartState = () => useContext(CartStateContext);
export const useCartDispatch = () => useContext(CartDispatchContext);
I'm developing a pokedex using pokeAPI through react, but I'm developing a feature where I can favorite pokemons and with that through a context, I can store the names of these pokemons in a global array. I've already managed to test and verify that the pokemon names are going to this "database" array inside the pokeDatabase const in my context, but my goal now is to pass this array to localstorage so that the browser recognizes these favorite pokemons instead of disappearing every time I refresh the page, my solution was to try to create a useEffect inside the context so that every time I refresh my application, this information is saved in localStorage, but without success. What better way to achieve this?
context:
import { createContext } from "react";
const CatchContext = createContext({
pokemons: null,
});
export default CatchContext;
provider
import React, { useEffect } from "react";
import CatchContext from "./Context";
const pokeDatabase = {
database: [],
};
const CatchProvider = ({ children }) => {
useEffect(() => {
const dataStorage = async () => {
await localStorage.setItem('pokemons', JSON.stringify(pokeDatabase.database));
}
dataStorage();
}, [])
return (
<CatchContext.Provider value={{ pokemons: pokeDatabase }}>
{children}
</CatchContext.Provider>
);
}
export default CatchProvider;
pageAddPokemon
import * as C from './styles';
import { useContext, useEffect, useState } from 'react';
import { useApi } from '../../hooks/useApi';
import { useNavigate, useParams } from 'react-router-dom';
import PokeInfo from '../../components/PokeInfo';
import AddCircleOutlineIcon from '#mui/icons-material/AddCircleOutline';
import DoNotDisturbOnIcon from '#mui/icons-material/DoNotDisturbOn';
import CatchContext from '../../context/Context';
const SinglePokemon = () => {
const api = useApi();
const { pokemons } = useContext(CatchContext);
const { name } = useParams();
const navigate = useNavigate();
const handleHompage = () => {
navigate('/');
}
const [loading, setLoading] = useState(false);
const [imgDatabase, setImgDatabase] = useState('');
const [infoPokemon, setInfoPokemon] = useState([]);
const [pokemonTypes, setPokemonTypes] = useState([]);
const [isCatch, setIsCatch] = useState(false);
useEffect(() => {
const singlePokemon = async () => {
const pokemon = await api.getPokemon(name);
setLoading(true);
setImgDatabase(pokemon.sprites);
setInfoPokemon(pokemon);
setPokemonTypes(pokemon.types);
setLoading(false);
console.log(pokemons.database);
}
singlePokemon();
verifyPokemonInDatabase();
}, []);
const verifyPokemonInDatabase = () => {
if (pokemons.database[infoPokemon.name]) {
return setIsCatch(true);
} else {
return setIsCatch(false);
}
}
const handleCatchAdd = async () => {
if (isCatch === false) {
if (!pokemons.database[infoPokemon.name]);
pokemons.database.push(infoPokemon.name);
setIsCatch(true);
}
}
const handleCatchRemove = async () => {
if (isCatch === true) {
if (!pokemons.database[infoPokemon.name]);
pokemons.database.splice(pokemons.database.indexOf(toString(infoPokemon.name)), 1);
setIsCatch(false);
}
}
return (
<C.Container>
<PokeInfo
name={infoPokemon.name}
/>
<C.Card>
<C.Info>
<C.Imgs>
<img src={imgDatabase.front_default} alt="" />
<img src={imgDatabase.back_default} alt="" />
</C.Imgs>
<h2 id='types'>Tipos</h2>
{pokemonTypes.map(type => {
return (
<C.Types>
<h2>{type.type.name}</h2>
</C.Types>
)
})}
{isCatch ? (
<DoNotDisturbOnIcon id='iconCatched' onClick={handleCatchRemove}/>
): <AddCircleOutlineIcon id='icon' onClick={handleCatchAdd}/>}
</C.Info>
</C.Card>
<C.Return>
<button onClick={handleHompage}>Retornar a Pokédex</button>
</C.Return>
</C.Container>
)
}
export default SinglePokemon;
I am trying to optimize my react application, while profiling my application I found that when I click on Add to cart page my whole page is getting re-rendered. Could anyone help me with, how to avoid that and why it is happening?
FYR, GitHub repo:https://github.com/sandeep8080/shopping-cart-assignment
import { useCallback, useEffect, useState } from "react";
import { useDispatch, useSelector } from "react-redux";
import SideBar from "../../components/sideBar/SideBar";
import { getProductsData } from "../../redux/action/products";
import ProductCard from '../../components/productCard/ProductCard';
import './products.css';
import { getCategoryData } from "../../redux/action/category";
import Cart from "../cart/cart";
import Modal from '../../components/modal/Modal';
import { useHistory, useParams } from "react-router";
const ProductsPage = () => {
const dispatch = useDispatch();
const router = useHistory();
const { id } = useParams();
console.log(` product comp : ${id}`);
const productsData = useSelector(data => data.Products.products);
const sideBarData = useSelector(data => {
const listItems = data.Categories.CategoriesItems;
const activeListItems = listItems.filter(item => item.enabled === true);
return activeListItems;
});
const openCart = useSelector(state => state.CartDetails.isOpen);
const [fProductData, setFProductData] = useState([]);
useEffect(() => {
dispatch(getProductsData());
dispatch(getCategoryData());
}, []);
useEffect(() => {
if (id) {
filterDataByCategory(id);
} else {
setFProductData(productsData);
}
}, [productsData, id]);
// Function to filter out the data based on category
const filterDataByCategory = (id) => {
console.log("Filter data function called")
const filterData = productsData.filter(item => item.category === id);
setFProductData(filterData);
};
const handleClickProduct = useCallback((id) => {
filterDataByCategory(id);
router.push(`/products/${id}`);
}, [id]);
return (
<div className='product-main'>
<SideBar
sideBarData={sideBarData}
handleClickProduct={handleClickProduct}
/>
<div className='product-container'>
<div className='product-row'>
{
(fProductData).map((product) => {
return (
<div key={product.id} className='card-wrapper' >
<ProductCard key={product.id} {...product} />
</div>
)
})
}
</div>
</div>
{
openCart &&
<Modal>
<Cart />
</Modal>
}
</div >
)
};
export default ProductsPage;
// Product Card component
import './ProductCard.css';
import Button from '../button/Button';
import React from 'react';
import { useDispatch } from 'react-redux';
import { updateCart } from '../../redux/action/cart';
import priceFromatter from '../../lib/priceFromatter';
const ProductCard = ({ name, price, description, imageURL, id }) => {
const dispatch = useDispatch();
const handleClick = () => {
console.log('product clicked', id);
dispatch(updateCart(id, 'add'));
};
let imgURL = `../../${imageURL}`;
// imgURL = imgURL.replace(/([^:]\/)\/+/g, "$1");
// const image = React.lazy(() => import (`${imgURL}`));
// console.log(image);
return (
<article className='card-container'>
<h6 className='card-header'>
{name}
</h6>
<div className='content-container'>
<img
className='content-img'
// src={require(`${imgURL}`).default}
src={imageURL}
/>
<div className='content'>
<p className='content-desc'>{description}</p>
<div className='content-footer'>
<p>{priceFromatter(price)}</p>
<Button btnText='Add To Cart' handleClick={() => handleClick(id)} />
</div>
</div>
</div>
</article>
)
};
export default ProductCard;
import { callApi } from "../../lib/api";
import { actions } from '../actionContants/actionConstant';
export const toggleCart = (isToggle) => {
return {
type: actions.OPEN_CART,
payload: isToggle,
}
};
export const updateCart = (id, operation) => {
return async (dispatch, getState) => {
const productList = getState().Products.products;
const cartItems = getState().CartDetails.cartItems;
const currItem = productList.find(({ id: currentItemId }) => currentItemId === id);
const isItemInCart = cartItems.find(({ id }) => id === currItem.id);
let finalItem = [];
if (!isItemInCart) {
finalItem = [...cartItems, { ...currItem, count: 1 }]
} else {
finalItem = cartItems.map(item => {
if (item.id === currItem.id) {
operation === 'add' ? item.count = item.count + 1 : item.count = item.count - 1
}
return item;
}).filter(({ count }) => count)
}
try {
const result = await callApi.post('/addToCart', id);
result && dispatch({
type: actions.UPDATE_TO_CART,
payload: finalItem
})
} catch (error) {
console.log(error)
}
}
};
In products.js change the following block of code:
const sideBarData = useSelector(data => {
const listItems = data.Categories.CategoriesItems;
const activeListItems = listItems.filter(item => item.enabled === true);
return activeListItems;
});
to:
const sideBarData = useSelector(data => {
const listItems = data.Categories.CategoriesItems;
const activeListItems = listItems.filter(item => item.enabled === true);
return activeListItems;
}, shallowEqual);
useSelector will force a component to re-render when the selector returns a new reference that is different than the previous reference (it uses the === operator). Ref: https://react-redux.js.org/api/hooks#equality-comparisons-and-updates. As you are filtering the array returned from the store, it will always be a different object reference to the one in the store.
The use of shallowEqual as the equalityFn to useSelector() can be used to change the comparison and prevent an unnecessary re-render of the <ProductsPage> component.
did you try using e.preventDefault() otherwise the answer above might work
React console logs the data variable before the filter function is finished. I want to load the data into the data variable if the blog id matched the params id. But data variable is console logged before the function is finished.
import React, { useContext, useEffect, useState } from "react";
import { BlogDataContext } from "../contexts/BlogDataContext";
export default function BlogPage({ match }) {
var Id = match.params.id;
const context = useContext(BlogDataContext);
const [Blog, setBlog] = useState();
useEffect(() => {
var data = context.filter((b) => {
return b._id === Id;
});
console.log(data);
setBlog(data);
}, []);
return (
<div style={{ color: "red" }} className="BlogPage">
hello
</div>
);
}
Try to put context in useEffect dependency array:
import React, { useContext, useEffect, useState } from "react";
import { BlogDataContext } from "../contexts/BlogDataContext";
export default function BlogPage({ match }) {
var Id = match.params.id;
const context = useContext(BlogDataContext);
const [Blog, setBlog] = useState();
useEffect(() => {
var data = context.filter((b) => {
return b._id === Id;
});
console.log(data);
setBlog(data);
}, [context]);
return (
<div style={{ color: "red" }} className="BlogPage">
hello
</div>
);
}
I am checking to see if isFetchingData then don't render yet but its not re-rendering once isFetchingData is set to false. I have the useEffect in the context and i would hope that would re-render once isFetchingData is set to false. Any ideas?
When I refresh the page it renders with the data. So I think its to do with re-rendering.
I am using react context to get the data and exposing functions to filter that data and get me what i need.
Context:
import React, { useEffect, useState } from 'react';
import getAllEmployees from 'my-services/employee/getAllEmployees';
import { arrayOf, node, oneOfType } from 'prop-types';
export const EmployeeContext = React.createContext({
allEmployees: [],
getActiveEmployees: () => [],
getTerminatedEmployees: () => []
});
const EmployeesProvider = ({ children }) => {
const [isFetchingData, setIsFetchingData] = useState(true);
const [allEmployees, setAllEmployees] = useState({});
useEffect(() => {
getAllEmployees().then(
//doing something
).then(employees => {
setAllEmployees(employees);
setIsFetchingData(false);
});
}, [isFetchingData])
const context = {
isFetchingData,
allEmployees,
getActiveEmployees: () =>
allEmployees.filter(x => x.status === 'Current'),
getTerminatedEmployees: () =>
allEmployees.filter(x => x.status === 'Terminated')
};
return (
<EmployeeContext.Provider value={context}>{children}</EmployeeContext.Provider>
);
};
EmployeesProvider.propTypes = {
children: oneOfType([node, arrayOf(node)])
};
EmployeesProvider.defaultProps = {
children: undefined
};
export default EmployeesProvider;
Component:
import React, { useContext } from 'react';
import styled from 'styled-components';
import { EmployeeContext } from 'my-contexts/EmployeeContext';
import EmployeeCard from '../../../components/EmployeeCard';
const EmployeesTab = () => {
const {
getActiveEmployees,
getTerminatedEmployees,
isFetchingData
} = useContext(EmployeeContext);
let activeEmployees = [];
let terminatedEmployees = [];
if (!isFetchingData) {
activeEmployees = getActiveEmployees();
terminatedEmployees = getTerminatedEmployees();
}
if(isFetchingData) {
return <p>Loading</p>;
}
return (
<Outer>
<TopHeader>
<H3>Employees ({activeEmployees.length})</H3>
</TopHeader>
<Wrapper>
{activeEmployees.map(employee => {
return (
<EmployeeCard
id={employee.id}
guid={employee.guid}
firstName={employee.name.first}
lastName={employee.name.last}
jobTitle={employee.jobTitle}
/>
);
})}
</Wrapper>
<H3>Terminated employees({terminatedEmployees.length})</H3>
<Wrapper>
{terminatedEmployees.map(employee => {
return (
<EmployeeCard
id={employee.id}
guid={employee.guid}
firstName={employee.name.first}
lastName={employee.name.last}
jobTitle={employee.jobTitle}
/>
);
})}
</Wrapper>
</Outer>
);
};
export default EmployeesTab;
I think many problems may exist.
At first, please check whether whole component is closed by context Provider.
For example
<EmployeesProvider>
<EmployeesTab/>
<EmployeesProvider/>
Please check this problem.