I'm new to React and am tripping over this issue.
Have read couple of tutorials and questions here to find out about how Parent & Child Components should communicate. However, I am unable to get the data to populate the fields + make it editable at the same time. I'll try explain further in code below:
Parent Component:
...imports...
export default class Parent extends Component {
constructor(props) {
this.state = {
data: null
};
}
componentDidMount() {
API.getData()
.then((response) => {
this.setState({ data: response });
// returns an object: { name: 'Name goes here' }
})
}
render() {
return (
<Fragment>
<ChildComponentA data={this.state.data} />
<ChildComponentB data={this.state.data} />
</Fragment>
);
}
}
Input Hook: (source: https://rangle.io/blog/simplifying-controlled-inputs-with-hooks/)
import { useState } from "react";
export const useInput = initialValue => {
const [value, setValue] = useState(initialValue);
return {
value,
setValue,
reset: () => setValue(""),
bind: {
value,
onChange: event => {
setValue(event.target.value);
}
}
};
};
ChildComponent:* (This works to allow me to type input)
import { Input } from 'reactstrap';
import { useInput } from './input-hook';
export default function(props) {
const { value, setValue, bind, reset } = useInput('');
return (
<Fragment>
<Input type="input" name="name" {...bind} />
</Fragment>
);
}
ChildComponent Component:
(Trying to bind API data - Input still editable but data is still not populated even though it is correctly received.. The API data takes awhile to be received, so the initial value is undefined)
import { Input } from 'reactstrap';
import { useInput } from './input-hook';
export default function(props) {
const { value, setValue, bind, reset } = useInput(props.data && props.data.name || '');
return (
<Fragment>
<Input type="input" name="name" {...bind} />
</Fragment>
);
}
ChildComponent Component:
(Trying to use useEffect to bind the data works but input field cannot be typed..)
I believe this is because useEffect() is trigged every time we type.. and props.data.name is rebinding its original value
import { Input } from 'reactstrap';
import { useInput } from './input-hook';
export default function(props) {
const { value, setValue, bind, reset } = useInput(props.data && props.data.name || '');
useEffect(() => {
if(props.data) {
setValue(props.data.name);
}
});
return (
<Fragment>
<Input type="input" name="name" {...bind} />
</Fragment>
);
}
I can think of a few tricks like making sure it binds only once etc.. But I'm not sure if it is the correct approach. Could someone share some insights of what I could be doing wrong? And what should be the correct practice to do this.
To iterate, I'm trying to bind API data (which takes awhile to load) in parent, and passing them down as props to its children. These children have forms and I would like to populate them with these API data when it becomes available and yet remain editable after.
Thanks!
Basic way to create your Parent/Child Component structure is below, I believe. You don't need a class-based component for what you are trying to achieve. Just add an empty array as a second argument to your useEffect hook and it will work as a componentDidMount life-cycle method.
Parent component:
import React, {useState, useEffect} from 'react';
export default const Parent = () => {
const [data, setData] = useState({});
const [input, setInput] = useState({});
const inputHandler = input => setInput(input);
useEffect(() => {
axios.get('url')
.then(response => setData(response))
.catch(error => console.log(error));
}, []);
return <ChildComponent data={data} input={input} inputHandler={inputHandler} />;
};
Child Component:
import React from 'react';
export default const ChildComponent = props => {
return (
<div>
<h1>{props.data.name}</h1>
<input onChange={(e) => props.inputHandler(e.target.value)} value={props.input} />
</div>
);
};
Related
I'm getting a placeholder value through props in my input component and I need to send the input value back to the main class. I'm using React but I'm not getting it. Follow my code.... The value I need to send is the value of 'usuario'
import React, { useState } from 'react';
import { EntradaDados } from './styled';
const PesqDados = ({placeholder, usuario}) => {
const [usuario, SetUsuario] = useState('')
const setValor =(e)=>{
SetUsuario(e.target.value);
}
console.log(usuario);
return(
<EntradaDados
onChange={setValor}
placeholder={placeholder}
>
</EntradaDados>
);
}
export default PesqDados;
You need to add a callback prop (onUsuarioChange) to your PesqDados component and call it with the new usuario. You have two options:
Call it from a useEffect with usuario as dependency (assuming usuario could get updated from somewhere other than setValor.
Call it from setValor, assuming that's the only place where usuario is going to get updated from.
This is how this should look:
import React, { useState } from 'react';
import { EntradaDados } from './styled';
const PesqDados = ({
placeholder,
usuario,
onUsuarioChange
}) => {
const [usuario, setUsuario] = useState('');
// Option 1:
useEffect(() => {
onUsuarioChange(usuario);
}, [usuario]);
const setValor = (e) => {
const nextUsuario = e.target.value;
setUsuario(nextUsuario);
// Option 2:
onUsuarioChange(nextUsuario);
};
return (
<EntradaDados
onChange={ setValor }
placeholder={ placeholder } />
);
}
export default PesqDados;
After studying properly, I found that I don't need to implement the function in the component page. I just needed to create a hook that calls the component's OnChange property on the component's page and then create a function just in the place where the component is installed. In this case, App.js.
Page Component....
const PesqDados = ({placeholder, Dados}) => {
return(
<EntradaDados
onChange={Dados}
placeholder={placeholder}
>
</EntradaDados>
);
}
export default PesqDados;
Page App.js
function App() {
const [usuario, SetUsuario] = useState('Aguardando Dados...')
const setValor =(e)=>{
SetUsuario(e.target.value);
}
const teste = ()=>{
alert("O usuário digitado foi : "+usuario)
};
return (
<>
<div className='divRepos'>
<div className='bloco'>
<div className='pesquisar'>
<p>{usuario}</p>
<PesqDados
placeholder={"Digite um username válido"}
Dados={setValor}
/>
<Button nomeBotao={"Pesquisar Perfil"}
onClick={teste}/>
</div>
...
I am gathering posts (called latestFeed) from my backend with an API call. These posts are all mapped to components and have comments. The comments need to be opened and closed independently of each other. I'm governing this mechanic by assigning a piece of state called showComment to each comment. showComment is generated at the parent level as dictated by the Rules of Hooks.
Here is the parent component.
import React, { useState, useEffect } from "react";
import { getLatestFeed } from "../services/axios";
import Child from "./Child";
const Parent= () => {
const [latestFeed, setLatestFeed] = useState("loading");
const [showComment, setShowComment] = useState(false);
useEffect(async () => {
const newLatestFeed = await getLatestFeed(page);
setLatestFeed(newLatestFeed);
}, []);
const handleComment = () => {
showComment ? setShowComment(false) : setShowComment(true);
};
return (
<div className="dashboardWrapper">
<Child posts={latestFeed} showComment={showComment} handleComment={handleComment} />
</div>
);
};
export default Parent;
latestFeed is constructed along with showComment. After latestFeed comes back with an array of posts in the useEffect hook, it is passed to the child show here:
import React, { useState } from "react";
const RenderText = ({ post, showComment, handleComment }) => {
return (
<div key={post._id} className="postWrapper">
<p>{post.title}</p>
<p>{post.body}</p>
<Comments id={post._id} showComment={showComment} handleComment={() => handleComment(post)} />
</div>
);
};
const Child = ({ posts, showComment, handleComment }) => {
return (
<div>
{posts.map((post) => {
<RenderPosts posts={posts} showComment={showComment} handleComment={handleComment} />;
})}
</div>
);
};
export default Child;
However, whenever I trigger handleComments, all comments open for all posts. I'd like them to be only the comment that was clicked.
Thanks!
You're attempting to use a single state where you claim you want multiple independent states. Define the state directly where you need it.
In order to do that, remove
const [showComment, setShowComment] = useState(false);
const handleComment = () => {
showComment ? setShowComment(false) : setShowComment(true);
};
from Parent, remove the showComment and handleComment props from Child and RenderText, then add
const [showComment, handleComment] = useReducer(state => !state, false);
to RenderText.
Component A
const query = ....
getData(query);
Component B
//here I want to call it using component's A argument
You would probably have a parent around these two components. You can use the parent to share the function:
function Parent() {
const [ dataWithQuery, setDataWithQuery ] = useState(null);
return (
<>
<ComponentA setDataWithQuery={ setDataWithQuery } />
<ComponentB dataWithQuery={ dataWithQuery } />
</>
);
}
and in Component A you'd have:
function ComponentA({ setDataWithQuery }) {
const yourQueryHere = '...'
function getData(query) { ... }
useEffect(() => {
setDataWithQuery(() => getData(yourQueryHere));
}, []);
...
}
Notice the line where I setDataWithQuery(...), I created a new function that calls getData with your query variable. This is how you save the function parameter to be used outside of ComponentA.
and in Component B you'd have:
function ComponentB({ dataWithQuery }) {
useEffect(() => {
if(dataWithQuery != null) {
const data = dataWithQuery();
}
}, [ dataWithQuery ]);
...
}
But there is no real reason to structure like this. Why not pass up the query from ComponentA to a parent, get the data from the parent using that query, then pass that data to ComponentB?
Edit: you could also look up React Contexts for sharing without passing up and down parent/child. There would still need to be a parent around.
Do you mean, you want to pass a query down to ComponentA, get the data from within it, then use that data in ComponentB?
If that is not what you want and you want to use the same query in each one, then just keep the query parameter in the component above them post and pass them down in props.
If the former is what you want:
Parent Component:
import "./styles.css";
import ComponentA from "./ComponentA";
import ComponentB from "./ComponentB";
import { useState } from "react";
export default function App() {
const [query, setQuery] = useState("get some data");
const [data, setData] = useState({});
return (
<div className="App">
<ComponentA query={query} setData={setData} />
<ComponentB data={data} />
</div>
);
Component A
import React, { useEffect } from "react";
function ComponentA({ query, setData }) {
useEffect(() => {
if (query !== "") {
getData(query);
}
}, [query]);
async function getData(query) {
//do some stuff
const result = { id: "1", message: "I am data" };
setData(result);
}
return (
<div>
<h1>I am component A</h1>
</div>
);
}
export default ComponentA;
ComponentB
function ComponentB({ data }) {
function doSomethingWithComponentAData() {
//do stuff with the data from componentA
}
return (
<div>
<h1>I am Component B, I got data: {data.id}</h1>
</div>
);
}
export default ComponentB;
Try this:
// Component A
export const getData = () => { // ... }
// Component B
import { getData } from './ComponentA'
const result = getData()
I have the below common component
import PropTypes from 'prop-types';
import Input from '../component/Input'; //internal component
const CustomInput = props => {
const { label, updateInputField } = props;
return (
<Input
label={label}
changeField={updateInputField}
)
}
CustomInput.propTypes = {
label: PropTypes.string,
updateInputField: PropTypes.func
}
export default CustomInput;
Now i am using these component at several places like below
<CustomInput
label="401Balance"
updateInputField={inputFieldHandler}
/>
so this one works.. but there are some places where I am not using the updateInputField as a prop. for e.g.
<CustomInput
label="savingsBalance"
/>
How do i not pass the prop and ensure it doesnot fail. Can someone please suggest.
You could either set a default value to secure the case if no function was passed:
const { label, updateInputField = () => {} } = props;
or (probably a better approach) - create a separate function and add a simple condition:
const CustomInput = props => {
const { label, updateInputField } = props;
const fn = () => {
if (updateInputField) {
updateInputField();
}
};
return (
<Input
label={label}
changeField={fn}
/>
);
}
import React, { useState } from "react";
import Child from "./Child";
import "./styles.css";
export default function App() {
let [state, setState] = useState({
value: ""
});
let handleChange = input => {
setState(prevValue => {
return { value: input };
});
console.log(state.value);
};
return (
<div className="App">
<h1>{state.value}</h1>
<Child handleChange={handleChange} value={state.value} />
</div>
);
}
import React from "react";
function Child(props) {
return (
<input
type="text"
placeholder="type..."
onChange={e => {
let newValue = e.target.value;
props.handleChange(newValue);
}}
value={props.value}
/>
);
}
export default Child;
Here I am passing the data from the input field to the parent component. However, while displaying it on the page with the h1 tag, I am able to see the latest state. But while using console.log() the output is the previous state. How do I solve this in the functional React component?
React state updates are asynchronous, i.e. queued up for the next render, so the log is displaying the state value from the current render cycle. You can use an effect to log the value when it updates. This way you log the same state.value as is being rendered, in the same render cycle.
export default function App() {
const [state, setState] = useState({
value: ""
});
useEffect(() => {
console.log(state.value);
}, [state.value]);
let handleChange = input => {
setState(prevValue => {
return { value: input };
});
};
return (
<div className="App">
<h1>{state.value}</h1>
<Child handleChange={handleChange} value={state.value} />
</div>
);
}
Two solution for you:
- use input value in the handleChange function
let handleChange = input => {
setState(prevValue => {
return { value: input };
});
console.log(state.value);
};
use a useEffect on the state
useEffect(()=>{
console.log(state.value)
},[state])
Maybe it is helpful for others I found this way...
I want all updated projects in my state as soon as I added them
so that I use use effect hook like this.
useEffect(() => {
[temp_variable] = projects //projects get from useSelector
let newFormValues = {...data}; //data from useState
newFormValues.Projects = pro; //update my data object
setData(newFormValues); //set data using useState
},[projects])