I know this could be a noob question but I'm learning React for a few months and now I'm stucked with this problem. I got this code over here:
import React, { useCallback, useEffect, useRef, useState } from 'react'
import ReactTags from 'react-tag-autocomplete'
const TagsHandler = ({ tagPlaceholder, suggestions }) => {
const [tags, setTags] = useState([])
const reactTags = useRef()
const onDelete = useCallback(
(tagIndex) => {
setTags(tags.filter((_, i) => i !== tagIndex))
},
[tags]
)
const onAddition = useCallback(
(newTag) => {
setTags([...tags, newTag])
},
[tags]
)
useEffect(() => {
suggestions.map((suggestion) => {
suggestion.disabled = tags.some((tag) => tag.id === suggestion.id)
})
}, [tags])
return (
<ReactTags
ref={reactTags}
tags={tags}
suggestions={suggestions}
onDelete={onDelete}
onAddition={onAddition}
placeholderText={tagPlaceholder}
/>
)
}
export default TagsHandler
Which implements a tag list inside my parent component. This parent component has a bool value which enables a save button. I should enable this button whenever a user adds or removes a tag to the list. My question is: how can I handle this bool from the child component? I've read about Redux but I'd like to avoid using it. I was thinking about a SetState function or a callback but I can't figure out the syntax.
Any help would be really appreciated, thanks :)
You can simply create a function in your parent component: toggleButton, and pass the function to your child component.
function Parent = (props) => {
const [isToggle, setIsToggle] = useState(false);
const toggleButton = () => {
setIsToggle(!isToggle)
}
return <Child toggled={isToggle} toggle={toggleButton} />
}
So the general approach is as follows:
In the Parent.jsx:
const [childrenActive, setChildrenActive] = useState(false)
// later in the render function
<Children setIsActive={(newActive) => setChildrenActive(newActive)} />
In the Children.jsx:
const Children = ({ setIsActive }) => {
return <button onClick={() => setIsActive(true)}>Click me</button>
}
So, as you have guessed, we pass a callback function. I would avoid passing setState directly because it makes your component less flexible.
In the parent component, the function that is responsible for changing that bool variable, you pass as a prop to the child component. At the child component you get that props and you can update if you want.
Related
I'm having an issue with react memo when using nextjs. In the _app e.g. I have a button imported:
import { ChildComponent } from './ChildComponent';
export const Button = ({ classN }: { classN?: string }) => {
const [counter, setCounter] = useState(1);
const Parent = () => {
<button onClick={() => setCounter(counter + 1)}>Click me</button>
}
return (
<div>
{counter}
<Parent />
<ChildComponent />
</div>
);
};
Child component:
import React from 'react';
export const ChildComponent = React.memo(
() => {
React.useEffect(() => {
console.log('rerender child component');
}, []);
return <p>Prevent rerender</p>;
},
() => false
);
I made one working in React couldn't figure it out in my own app:
https://codesandbox.io/s/objective-goldwasser-83vb4?file=/src/ChildComponent.js
The second argument of React.memo() must be a function that returns true if the component don't need to be rerendered and false otherwise - or in the original definition, if the old props and the new props are equal or not.
So, in your code, the solution should be just change the second argument to:
export const ChildComponent = React.memo(
() => { ... },
// this
() => true
);
Which is gonna tell React that "the props didn't change and thus don't need to rerender this component".
So my issue was that I made a function called Button and returned inside a button or Link. So I had a mouseEnter inside the button which would update the state and handle the function outside the function. Kinda embarrassing. This fixed it. So the only change was I moved usestate and handlemousehover inside the button function.
const Button = () => {
const [hover, setHover] = useState(false);
const handleMouseHover = (e: React.MouseEvent<HTMLElement>) => {
if (e.type === 'mouseenter') {
setHover(true);
} else if (e.type === 'mouseleave') setHover(false);
};
return (
<StyledPrimaryButton
onMouseEnter={(e) => handleMouseHover(e)}
onMouseLeave={(e) => handleMouseHover(e)}
>
<StyledTypography
tag="span"
size="typo-20"
>
{title}
</StyledTypography>
<ChildComponent />
</StyledPrimaryButton>
);
};
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.
I am transfer an props from father component to child component.
On the child component I want to check if the father component is deliver the props,
If he does, i"m putting it on the state, If not I ignore it.
if(Object.keys(instituteObject).length > 0)
{
setInnerInstitute(instituteObject)
}
For some reason the setInnerInstitute() take me to infinite loop.
I don't know why is that happening and how to fix it.
getInstitutesById() - Is the api call to fetch the objects.
Father component(EditInstitute):
const EditInstitute = props => {
const {id} = props.match.params;
const [institute, setInstitute] = useState({})
useEffect(() => { //act like componentDidMount
getInstitutesById({id}).then((response) => {
setInstitute(response)
})
// eslint-disable-next-line react-hooks/exhaustive-deps
}, [])
return (
<React.Fragment>
<InstituteForm instituteObject={institute.object}/>
</React.Fragment>
)
}
Child component(InstituteForm):
const InstituteForm = (props) => {
const {instituteObject = {}} = props // if not exist default value = {}
const [innerInstitute, setInnerInstitute] = useState({})
if (Object.keys(instituteObject).length > 0) // if exists update the state.
{
setInnerInstitute(instituteObject)
}
return (
<React.Fragment>
not yet.
</React.Fragment>
)
}
Thanks
I think the way you are changing your InstituteForm's state causing this error. You can try using the useEffect hook to change your innerInstitute based on instituteObject. That's why you need to also add instituteObject in the dependency array of that useEffect hook.
import { useEffect, useState } from "react"
const InstituteForm = (props) => {
const {instituteObject = {}} = props // if not exist default value = {}
const [innerInstitute, setInnerInstitute] = useState({})
useEffect(() => {
// this is be evoked only when instituteObject changes
if (Object.keys(instituteObject).length > 0){
setInnerInstitute(instituteObject)
}
}, [instituteObject])
return (
<React.Fragment>
not yet.
</React.Fragment>
)
}
When I enter into a router that refers to this Component, my browser just crashes. I've made some console tests and notices that when the response.data.message is up, it continually re-renders the page. Can someone help me?
import React from 'react'
import "./UsernameStory.css";
import Axios from "axios";
const UsernameStory = ({match}) => {
const [statue , setStatue] = React.useState("");
const [stories , setStories] = React.useState([]);
const fetchUsername = () => {
const urls = match.params.username;
Axios.post("http://localhost:8080/"+urls, {
}).then((response) => {
if(response.data.statue)
{
setStatue(response.data.statue);
}
if(response.data.message){
setStories(response.data.message);
}
})
}
return (
<div>
{fetchUsername()}
<p>{statue}</p>
<ul>
{stories.map((story , key) => (<li key={key}>{story.username}</li>))}
</ul>
</div>
)
}
export default UsernameStory
On every render, fetchUsername() is called and results in updating statue and stories, which results in another rerender, and thus leads to an infinite loop of rerendering (since every render triggers a state update).
A better practice for handling functions with side-effects like fetching data is to put the fetchUsername in useEffect.
const UsernameStory = ({match}) => {
const [statue , setStatue] = React.useState("");
const [stories , setStories] = React.useState([]);
useEffect(() => {
const urls = match.params.username;
Axios.post("http://localhost:8080/"+urls, {})
.then((response) => {
if(response.data.statue)
{
setStatue(response.data.statue);
}
if(response.data.message){
setStories(response.data.message);
}
});
}, []); // An empty denpendency array allows you to fetch the data once on mount
return (
<div>
<p>{statue}</p>
<ul>
{stories.map((story , key) => (<li key={key}>{story.username}</li>))}
</ul>
</div>
)
}
export default UsernameStory
You can't call function fetchUsername() inside return statement. It
will go in infinite loop.
You can't directly set the state of two variable as setStatue(response.data.statue) & setStories(response.data.message) respectively
use the useEffect hooks and set the status inside that hooks with conditional rendering to avoid looping.
call the fetchUsername() just before the return statement.
I looked at your code carefully. As you can see in this code, the fetchUsername() function is executed when the component is first rendered.
When you call setState() in the fetchUsername function, your component's state variable is updated. The problem is that when the state variable is updated, the component is rendered again. Then the fetchUsername function will be called again, right?
Try the useEffect Hook.
The example code is attached.
eg code
How about trying to change the way you call the fetchUsername() function with the useEffect hook instead?
import React, { useEffect } from 'react'
import "./UsernameStory.css";
import Axios from "axios";
const UsernameStory = ({match}) => {
const [statue , setStatue] = React.useState("");
const [stories , setStories] = React.useState([]);
useEffect(() => {
const fetchUsername = () => {
const urls = match.params.username;
Axios.post("http://localhost:8080/"+urls, {
}).then((response) => {
if(response.data.statue)
{
setStatue(response.data.statue);
}
if(response.data.message){
setStories(response.data.message);
}
})
}
fetchUsername();
// clean up here
return () => {
// something you wanna do when this component being unmounted
// console.log('unmounted')
}
}, [])
return (
<div>
<p>{statue}</p>
<ul>
{stories.map((story , key) => (<li key={key}>{story.username}</li>))}
</ul>
</div>
)
}
export default UsernameStory
But, sometimes your code just doesn't need a cleanup in some scenarios, you could read more about this here: Using the Effect Hook - React Documentation.
Below is my code.
CHILD COMPONENT
const onSave = () => {
var val = value
props.onSave();
}
<div onClick={() => { onSave() }}>
<CheckButton variant="contained" text-align='center' />
</div>
PARENT COMPONENT
export const Card = (props) => {
const onSave = (val) => { [I WANT TO ACCESS val within here] }
}
<TextInputContainer onSave={() => onSave()} />
Is there any way I can access that variable val inside the parent component? The code is truncated big-time. The actual code uses Redux.
The createRef of react helps u to access the value of a react component:
Reference (https://pt-br.reactjs.org/docs/hooks-reference.html)
constructor () {this.CheckButtonRef = createRef()}
onSave = () => {props.onSave(this.CheckButtonRef.current.value)}
<CheckButton ref = {this.CheckButtonRef}/>