The Parent (MyList in my example) component renders an array thru a Child (MyComponent) component. Parent decides to change properties in the array, what is React way of triggering child re-rendering?
All I came up with is this.setState({}); in Parent after tweaking the data. Is this a hack or a React way of triggering an update?
JS Fiddle: https://jsfiddle.net/69z2wepo/7601/
var items = [
{id: 1, highlighted: false, text: "item1"},
{id: 2, highlighted: true, text: "item2"},
{id: 3, highlighted: false, text: "item3"},
];
var MyComponent = React.createClass({
render: function() {
return <div className={this.props.highlighted ? 'light-it-up' : ''}>{this.props.text}</div>;
}
});
var MyList = React.createClass({
toggleHighlight: function() {
this.props.items.forEach(function(v){
v.highlighted = !v.highlighted;
});
// Children must re-render
// IS THIS CORRECT?
this.setState({});
},
render: function() {
return <div>
<button onClick={this.toggleHighlight}>Toggle highlight</button>
{this.props.items.map(function(item) {
return <MyComponent key={item.id} text={item.text} highlighted={item.highlighted}/>;
})}
</div>;
}
});
React.render(<MyList items={items}/>, document.getElementById('container'));
The problem here is that you're storing state in this.props instead of this.state. Since this component is mutating items, items is state and should be stored in this.state. (Here's a good article on props vs. state.) This solves your rendering problem, because when you update items you'll call setState, which will automatically trigger a re-render.
Here's what your component would look like using state instead of props:
var MyList = React.createClass({
getInitialState: function() {
return { items: this.props.initialItems };
},
toggleHighlight: function() {
var newItems = this.state.items.map(function (item) {
item.highlighted = !item.highlighted;
return item;
});
this.setState({ items: newItems });
},
render: function() {
return (
<div>
<button onClick={this.toggleHighlight}>Toggle highlight</button>
{ this.state.items.map(function(item) {
return <MyComponent key={item.id} text={item.text}
highlighted={item.highlighted}/>;
}) }
</div>
);
}
});
React.render( <MyList initialItems={initialItems}/>,
document.getElementById('container') );
Note that I renamed the items prop to initialItems, because it makes it clear that MyList will mutate it. This is recommended by the documentation.
You can see the updated fiddle here: https://jsfiddle.net/kxrf5329/
I have found a nice solution using key attribute for re-render with React Hook. If we changed key property of a child component or some portion of React Component, it will re-render entirely. It will use when you need to re-render some portion of React Component of re-render a child component. Here is a example. I will re-render the full component.
import React, { useState, useEffect } from "react";
import { PrEditInput } from "./shared";
const BucketInput = ({ bucketPrice = [], handleBucketsUpdate, mood }) => {
const data = Array.isArray(bucketPrice) ? bucketPrice : [];
const [state, setState] = useState(Date.now());
useEffect(() => {
setState(Date.now());
}, [mood, bucketPrice]);
return (
<span key={state}>
{data.map((item) => (
<PrEditInput
key={item.id}
label={item?.bucket?.name}
name={item.bucketId}
defaultValue={item.price}
onChange={handleBucketsUpdate}
mood={mood}
/>
))}
</span>
);
};
export default BucketInput;
An easy option to re-render a child is to update a unique key attribute every time you need a re-render.
<ChildComponent key={this.state.updatedKey}/>