Hy!
I am having an issue with my react code. My task is to call from iTunes API which i do with fetch then I process the data. But I cannot save it as a variable to be able to pass it around later.
import React, { Component } from 'react';
class SearchField extends Component{
constructor(props) {
super(props);
this.state = {value: ''};
this.handleChange = this.handleChange.bind(this);
this.handleSubmit = this.handleSubmit.bind(this);
}
handleChange = (event) => {
this.setState({value: event.target.value});
}
handleSubmit = (event) => {
event.preventDefault();
fetch(`https://itunes.apple.com/search?media=music&term=${this.state.value.toLowerCase()}`)
.then((resp) => resp.json())
.then(searchRes => searchRes.results[0].artistName)
.catch(err => console.log(err));
}
render() {
return(
<section className="hero is-primary">
<div className="hero-body">
<div className="container">
<form onSubmit={this.handleSubmit}>
<input className="input is-primary" type="text" value={this.state.value} onChange={this.handleChange} placeholder="Search for artist" />
<input className="button is-info" type="submit" value="Search" />
</form>
</div>
</div>
</section>
)
}
}
export default SearchField;
I'd have to use the fetched data later, i just need the artist name first.
If I log the value (searchRes.results[0].artistName, i get the correct value, but if i want to save it for later use i only got empty console.log back.
I've tried several approaches but I never get my result back.
Help me out please.
Remember that data flow in React is unidirectional. If you want to share the data around your app the search component should not be the component that fetches the data. That should be left to a parent component (maybe App). That component should have a function that handles the fetch request, and you can then pass a reference to that function down to the search component to call when the button is clicked. Then, once that data is loaded, the parent (App) component can pass all the relevant data down to the child components.
Here's a quick mock-up based on your existing code:
class Search extends {
constructor(props) {
super(props);
this.state = { url: '' };
this.handleKey = this.handleKey.bind(this);
}
handleKey(e) {
const url = e.target.value;
this.setState({ url });
}
render() {
const { url } = this.state;
// grab the function passed down from App
const { fetchData } = this.props;
return (
<input onKeyUp={this.handleKey} value={url} />
// Call that function with the url when the button is clicked
<button onClick={() => fetchData(url)}>Click</button>
)
}
}
class App extends Component {
constructor(props) {
super(props);
this.state = { data: [] };
this.fetchData = this.fetchData.bind(this);
}
// App contains the fetch method
fetchData(url) {
fetch(url)
.then(res => res.json())
// Update the App state with the new data
.then(data => this.setState({ data });
}
render() {
const { data } = this.state;
// Sanity check - if the state is still empty of data, present
// a loading icon or something
if (!data.length) return <Spinner />
// otherwise return the rest of the app components
// passing in the fetch method as a prop for the search component
return (
<OtherComponent data={data} />
<Search fetchData={this.fetchData} />
)
}
}
Please specify what you mean by
but if i want to save it for later use i only got empty console.log back
I think the correct way to handle your problem is by passing a callback function to your component's props that gets called whenever you press search and a search result is found, like this: https://codesandbox.io/s/xpq171n1vz
Edit: Note that while this answer has been accepted and is a way to solve your problem, Andy's answer contains solid and elaborate advice on how to actually structure your components.
Related
I created a simple date picker react js, after that I call API and get some data from API in the console, now I want to fetch API data on the web page.
Here is the code i used to call API function, I want map response data on a web page
import React, { Component } from 'react'
import axios from 'axios'
class PostForm extends Component {
constructor(props) {
super(props)
this.state = {
key: '',
}
console.log(this.state)
}
changeHandler = e => {
this.setState({ [e.target.name]: e.target.value })
}
submitHandler = e => {
e.preventDefault()
axios
.get(`http://127.0.0.1:8000/hvals_hash?key=${this.state.key}`)
.then(response => {
console.log(response.data)
})
.catch(error => {
console.log(error)
})
}
render() {
const { key } = this.state
return (
<center><div>
<form onSubmit={this.submitHandler}>
<div>
<h2> DATE PICKER</h2><br></br>
<input
type="text"
name="key"
value={key}
onChange={this.changeHandler}
/>
</div>
<br></br>
<button type="submit">Submit</button>
</form>
</div></center>
)
}
}
export default PostForm
Here is the explanation for this issue you can refer here,
import React, { Component } from 'react'
import axios from 'axios'
class PostForm extends Component {
constructor(props) {
super(props)
this.state = {
key: '',
// Where data will be saved.
data: [],
}
console.log(this.state)
}
changeHandler = e => {
this.setState({ [e.target.name]: e.target.value })
}
submitHandler = e => {
e.preventDefault()
axios
.get(`http://127.0.0.1:8000/hvals_hash?key=${this.state.key}`)
.then(response => {
// Updating the state to trigger a re-render
this.setState({data: response.data});
console.log(response.data)
})
.catch(error => {
console.log(error)
})
}
render() {
const { key } = this.state
return (
<center><div>
<form onSubmit={this.submitHandler}>
<div>
<h2> DATE PICKER</h2><br></br>
<input
type="text"
name="key"
value={key}
onChange={this.changeHandler}
/>
</div>
<br></br>
<button type="submit">Submit</button>
</form>
<div>
{this.state.data.map((dataObjectToDisplay) => {
return (
<div>
{
<ol>{this.state.data}</ol>
}
</div>
);
})}
</div>
</div></center>
)
}
}
export default PostForm
add a state (add an object property to this.state) and inside the submit handler, after getting the response in Axios, use setState({[name of state]: response.data }).
That takes care of updating the state. As for where to display them, it is up to you.
You can copy the code anywhere inside the render method. If u want to display it under the form, paste it inside the div container after the form.
For better controlling of the state, you can check one of the state-management tools like redux or simply use global context and implement routing using react-router –
Credits to #MrCeRaYA
First you have to save the data somewhere inside the app. Create a state and use setState to update it. Now that you have the latest data, you can use JSX's magic to display them using map.
Example:
<div>
{this.state.data.map((dataObjectToDisplay) => {
return (
<div>
{/* Include your data in a way you want here, you can also replace the div with any other element (li) */}
</div>
);
})}
</div>
<div>
{this.state.data.map((dataObjectToDisplay) => {
return (
<div>
{/* Include your data in a way you want here, you can also replace the div with any other element (li) */}
</div>
);
})}
</div>
I'm using react.js and react-router-dom to create two pages. Form.js is the page where you enter your name in the form, and Confirmation.js is the page where you confirm the name.
I want to share the state of two classes. So, when you jump to another page from the link button, you will send the state at the same time. The sent state is received in the class constructor as this.state = props.history.location.state.
Many have omitted this code.
//Form.js
import React, { Component } from 'react'
import {Link} from 'react-router-dom'
class Form extends Component {
constructor(props) {
super(props);
const histState = props.history.location.state
this.state = histState == undefined ? {name: this.state} : histState
}
render() {
return (
<div>
<input type="text" onChange={this.handleFormInputChanged} value={this.state.name}/>
<Link to={pathname: "/confirmation" , state: this.state}>Send</Link>
</div>
)
}
}
//Confirmation.js
class Confirmation extends Component {
constructor(props) {
super(props);
this.state = props.history.location.state
}
render() {
return (
<div>
<div>Your Name : <span className="name">{this.state.name}</span></div>
<Link to={pathname: "/form" , state: this.state}>Edit</Link>
</div>
)
}
}
Now I can do what I want to do. However, I noticed that when the user pressed the browser back button on the Confirmation.js page, the state was not sent because it jumped to the Form.js page without pressing the Link component.
As a solution, I added the following code to Confirmation.js.
//Confirmation.js
componentWillUnmount() {
this.props.history.push("/form", this.state)
}
However, when I do a browser back this way and receive a state in the class constructor, props.history.location.state is undefined. And strangely, after a while or reloading, props.history.location.state is set to state normally.
//Form.js
constructor(props) {
...
console.log("Form constructor", props.history.location.state)
}
I want to resolve the time it takes for state to be set as the value of props.history.location.state, is there a solution?
You can pass basic parameters as route segments, like /form/:username, or you could use a query parameter like /form?username=Hiroaki, but passing around data more structured or complex via the url or location history seems inadvisable.
I think you'd save yourself a lot of pain by using context or setting up a simple orthogonal store to keep track of it as the user navigates.
Here's a sketch of how you might do it with context. Assuming the provider is above the router in the component hierarchy, the form state will persist through navigation (though not through page reloads). (I haven't tested any of this code. This is just to give you a sense of it.)
const [formState, setFormState] = useState({});
<FormStateContext.Provider value={formState}>
<Form onChange={setFormState} />
</FormStateContext.Provider>
const Form = ({ onChange }) => {
const formState = useContext(FormStateContext);
return (
<input name="username"
value={formState.username}
onChange={(e) => setFormState({ ...formState, username: e.target.value })}
/>
);
}
const Confirmation = () => {
const formState = useContext(FormStateContext);
return (
<div>Your Name: {formState.username}</div>
);
}
If your components aren't that big, you could do something like this instead of using a different route :
import React from "react";
import { render } from "react-dom";
import "./style.css";
const App = () => {
const [state, setState] = React.useState({isConfirmationMode: false});
const handleChange = e => setState({...state, [e.target.name]: e.target.value});
const confirm = () => {
console.log('confirmed');
// Here send you data or whatever you want
// then redirect wherever you want, I just display the form again
setState({...state, isConfirmationMode: false});
}
const cancel = () => {
// juste display the form again
setState({...state, isConfirmationMode: false});
}
const displayForm = () => (
<div>
name : <input type="text" name="name" value={state.name} onChange={handleChange} />
<button onClick={() => setState({...state, isConfirmationMode: true})}>Send</button>
</div>
);
return state.isConfirmationMode ?
<Confirmation name={state.name} confirm={confirm} cancel={cancel} /> :
displayForm()
};
// Here I created 'confirm' and 'cancel', but you might only need 'cancel'
const Confirmation = ({name, confirm, cancel}) => {
return (
<div>
Are you {name} ?<br />
<button onClick={confirm}>Confirm</button>
<button onClick={cancel}>Cancel</button>
</div>
);
}
render(<App />, document.getElementById("root"));
Here is the repro on Stackblitz. The idea is just to either display the form or a confirmation depending on the state of a simple boolean (I separated the confirmation in another component but here it could be part of the first one).
As the title states, I am making an api request, and then returning a component with the contents of the api request as the prop. However, idk why I keep getting this error.
App.js
showPicture = async () =>{
//console.log(KEY)
const response = await picOfTheDay.get('',{
params: {
date:this.date,
hd: true,
api_key: 'KEY'
}
});
//console.log()
this.setState({picDayFullDescription: response}, ()=>{
return <PictureOfTheDay date = {this.state.date} picture= {this.state.picDayFullDescription.url} description={this.state.picDayFullDescription.explanation} />
})
}
render(){
return(
<div>
{/* <PictureOfTheDay date = {this.state.date} picture= {this.state.picDayFullDescription.url} description={this.state.picDayFullDescription.explanation}/> */}
{this.showPicture()}
</div>
)
}
PictureOfTheDay.js
class PictureOfTheDay extends React.Component{
constructor(props){
super(props);
}
render(){
return(
<div>
Hello?
</div>
)
}
}
Can someone please point me to the right direction
Instead of calling the function in the render, I would rather put the component on the render and then call the fetch function on some lifecycle hook like componentDidMount.
This updates the state, hence re-rendering the component and the PictureOfTheDay... If the component does not work with an empty description etc which might be a cause of you wanting to make sure the fields are there, render it conditionally based on the needed information e.g {this.state.picDayFullDescription && ...}
// App.js
componentDidMount() {
this.showPicture();
}
showPicture = async () => {
const response = await picOfTheDay.get("", {
params: {
date: this.date,
hd: true,
api_key: "KEY",
},
});
this.setState({ picDayFullDescription: response });
}
render() {
return (
<div>
<PictureOfTheDay
date={this.state.date}
picture={this.state.picDayFullDescription.url}
description={this.state.picDayFullDescription.explanation}
/>
</div>
);
}
So I am attempting to learn react along with rails (Using rails purely as an API). Im making a simple to-do app and getting stuck when attempting to "Create" a list.
I have a "New List" component shown here, mostly taken from the react forms tutorial:
import React, { Component } from 'react';
import axios from 'axios';
class ListForm extends Component {
constructor(props) {
super(props);
this.state = {
title: '',
description: ''
};
this.handleSubmit = this.handleSubmit.bind(this);
}
handleChange(e) {
this.setState({[e.target.name]: e.target.value});
}
handleSubmit(e) {
console.log("Form submitted with: " + this.state.value)
e.preventDefault();
}
render() {
return (
<form onSubmit={this.handleSubmit}>
<label>
Title:
<input name="title" type="text" value={this.state.value} onChange={this.handleInputChange} />
</label>
<label>
Description:
<textarea name="description" value={this.state.value} onChange={this.handleInputChange} />
</label>
<input type="submit" value="Submit" />
</form>
);
}
}
export default ListForm;
I have my ListContainer shown here
import React, { Component } from 'react';
import axios from 'axios';
import List from './List';
import ListForm from './ListForm'
class ListContainer extends Component {
constructor(props){
super(props)
this.state = {
lists: []
}
this.addNewList = this.addNewList.bind(this)
}
componentDidMount() {
axios.get('/api/v1/lists.json')
.then(response => {
console.log(response)
this.setState({
lists: response.data
})
})
.catch(error => console.log(error))
}
addNewList(title, description) {
axios.post('/api/v1/lists.json', {
title: title,
description: description
})
.then(function (response) {
console.log(response);
const lists = [ ...this.state.lists, response.data ]
console.log(...this.state.lists)
this.setState({lists})
})
.catch(function (error) {
console.log(error);
});
}
render() {
return (
<div className="lists-container">
{this.state.lists.map( list => {
return (<List list={list} key={list.id} />)
})}
<ListForm onSubmit={this.addNewList} />
</div>
)
}
}
export default ListContainer;
My issue comes from a misunderstanding at the callback on submit. I understand that when I do an "onSubmit" on the form it's using addNewList function as a callback....but I really am not understanding how the connection from state in the ListForm is getting into that callback function. I obviously am doing something wrong because it does not work and currently console shows "Form submitted with: undefined" so it's not passing parameters correctly at all.
Im still pretty new to React and very rusty with JS (It's been a bit since i've used it so im sure there are some newbie mistakes here). Also axios is basically a "better" fetch fwiw.
I won't lie either, I don't exactly understand why we do this.handleSubmit = this.handleSubmit.bind(this); for example (along with the other similar ones)
You're so close! We just need to make a few adjustments.
First let's lose the bind statements, and just use arrow functions. Arrow functions have no this object, and so if you call on this inside that function, you will actually access the this object of your class instance. Neat.
Second, let's fix the typo on your handleChange function, so that your inputs are updating the component state properly.
Now, the real solution to your problem. You need to call the addNewList function in your parent component, ListContainer. How do we do that? Lets pass it down to the child component as a prop! You're almost there, but instead of using the keyword onSubmit={this.addNewList}, lets use something like handleSubmit instead. This is because onSubmit is actually a special keyword that will attach an event listener to the child component for submit, and we don't want that.
Now that your child component is taking in your function as a prop. We can call it inside the handleSubmit function. We then pass in the arguments, title and description. Now your child component is able to call the addNewList function in the parent component!
import React, { Component } from 'react';
import axios from 'axios';
import List from './List';
import ListForm from './ListForm'
class ListContainer extends Component {
constructor(props) {
super(props)
this.state = {
lists: []
}
this.addNewList = this.addNewList.bind(this)
}
componentDidMount() {
axios.get('/api/v1/lists.json')
.then(response => {
console.log(response)
this.setState({
lists: response.data
})
})
.catch(error => console.log(error))
}
addNewList(title, description) {
axios.post('/api/v1/lists.json', {
title: title,
description: description
})
.then(function (response) {
console.log(response);
const lists = [...this.state.lists, response.data]
console.log(...this.state.lists)
this.setState({ lists })
})
.catch(function (error) {
console.log(error);
});
}
render() {
return (
<div className="lists-container">
{this.state.lists.map(list => {
return (<List list={list} key={list.id} />)
})}
<ListForm handleSubmit={this.addNewList} />
</div>
)
}
}
export default ListContainer;
import React, { Component } from 'react';
import axios from 'axios';
class ListForm extends Component {
constructor(props) {
super(props);
this.state = {
title: '',
description: ''
};
}
handleChange = (e) => {
this.setState({ [e.target.name]: e.target.value });
}
handleSubmit = (e) => {
this.props.handleSubmit(this.state.title, this.state.description);
e.preventDefault();
}
render() {
return (
<form onSubmit={this.handleSubmit}>
<label>
Title:
<input name="title" type="text" value={this.state.value} onChange={this.handleChange} />
</label>
<label>
Description:
<textarea name="description" value={this.state.value} onChange={this.handleChange} />
</label>
<input type="submit" value="Submit" />
</form>
);
I think you have a typo as well. For the change event you have
<input name="title" type="text" value={this.state.value} onChange={this.handleInputChange} />
So the callback for change is this.handleInputChange. But in your code its called handleChange
But even if you've used the right naming, it will not work, because you need to bind that function as well.
That brings me to your question about this.handleSubmit = this.handleSubmit.bind(this);
The problem here is that when you pass a function as a callback it loses its context. Consider the following
const x = {
log: function() { console.log(this.val) },
val: 10
}
Now you can do
x.log(); // -> print 10
But when you do
y = x.log;
y(); // -> prints undefined
If you pass only the function around it looses its context. To fix this you can bind
x.log = x.log.bind(x);
y = x.log
y(); // -> prints 10
Hope this makes sense :)
Anyway, to come back to you question, you don't have to use bind, there is a better way
class ListForm extends Component {
constructor(props) {
super(props);
this.state = {
title: '',
description: ''
};
}
handleChange = (e) => {
this.setState({[e.target.name]: e.target.value});
}
handleSubmit = (e) => {
console.log("Form submitted with: " + this.state.value)
e.preventDefault();
}
Although not tests, it might work right now!
Change value property of the inputs with this.state.title & this.state.description:
<input name="title" type="text" value={this.state.title} onChange={this.handleInputChange} />
<textarea name="description" value={this.state.description} onChange={this.handleInputChange} />
try printing info using
console.log("Form submitted with: ", this.state)
Regards to the .bind(this) :
When any event fires, an event object is assigned to callback function. So callback function or event handlers loses reference to class and this points to whichever event has been called.
Bind creates a new function that will have this set to the first parameter passed to bind()
Apart from .bind(this) arrow function takes care for this. but it's not preferable for long hierarchy.
I'm new to React and wanted to play around with the fetchAPI. I want to use the GoogleBooks API to display a list of books that matches a query string which the user can enter in an input field.
I've managed to make the call to the Google API and have used setState but I can't get the state to stick. If I want to render the state after fetching the data, the state appears as undefined.
I have a feeling that React renders the HTML first and then sets the state after making the API call.
I'd appreciate if you can have a look at my component.
Thank you!
import React, {Component} from 'react'
class Search extends Component{
constructor(props){
super(props)
this.state = {
books: []
}
this.books = this.state.book
this.title = ''
this.handleChange = (e) => {
this.title = e.target.value
}
this.handleSubmit = (e) => {
let results = '';
e.preventDefault();
const apiKey = 'AIzaSyBuR7JI6Quo9aOc4_ij9gEqoqHtPl-t82g'
fetch(`https://www.googleapis.com/books/v1/volumes?q=${this.title}&key=${apiKey}`)
.then(response => response.json()).then(jsonData => {
this.setState({
books: jsonData
})
console.log(jsonData)
})
}
}
render(){
return(
<div className="col-md-12">
<form onSubmit={this.handleSubmit} className="form-group">
<label>Enter title</label>
<input onChange={this.handleChange} className="form-control" ref="title" type="text" placeholder="Enter title"></input>
<button type="submit" className="btn btn-primary">Submit</button>
</form>
<div>
<li>this.state.books</li>
</div>
</div>
You have:
<li>this.state.books</li>
This is just rendering a string.
Instead, you can use map to show data from book you get from the response.
Here's a working example:
<div>
{
this.state.books.items &&
this.state.books.items.map(book => <li>{book.etag}</li>)
}
</div>