I have a parent ButtonGroup component and the child buttonItem component:
//ButtonGroup Component (Parent)
clicky(){
//capture the props of the clicked button, ie, caption and disabled here.
}
render() {
return (
<div onClick={this.clicky}>
{this.props.children}
</div>
)
}
//buttonItem component:
render() {
return (
<button disabled={this.props.disabled}>{this.props.caption}</button>
)
}
//final render
<ButtonGroupComponent>
<buttonItem caption="Nothing"/>
<buttonItem caption="Something" disabled={true}/>
<buttonItem caption="Refresh"/>
</ButtonGroupComponent>
from the above code is there any way i can capture the props of the clicked child buttonItem?
In your case, you need to merge this.props.children with your custom prop. So, I suggest you use React.Children to operate with it.
By the way, after adding new prop you need to return this child, so cloneElement will help you with this.
Inside import section of ButtonGroupComponent:
import React, { Children, Component, cloneElement } from 'react';
Its render function will look like this:
render() {
const childrenWithCustomHandler = Children.map(this.props.children, itemChild => {
// Arguments of cloneElement (component, [customProps], [customChildren])
return cloneElement(itemChild, { onClickItem: this.clicky })
}
);
return <div>{childrenWithCustomHandler}</div>;
}
And the code of buttonItem component will look like:
return (
<button
disabled={this.props.disabled}
onClick={() => {
this.props.onClickItem({ ...this.props });
}}
>
{this.props.caption}
</button>
)
I used Spread operator to clone the object, so if you will want to change props in your clicky function, the child won't be rendered.
Related
I'm stuck because of many multiple solutions to the problem I have, but no clear explanation for a beginner like me.
I'm building my first todo list app.
I have an App file and a ToDo child component.
From the child Todo, I'm calling the deleteTodo method, included within my parent app component, using props, but the console doesn't display any result when I click on the button.
What am I missing?
ToDo.js (full code)
import React, { Component } from 'react';
class ToDo extends Component { //define a class that extends Component
render() {
return (
<li>
<span>{ this.props.description }</span>
<button onClick ={this.props.deleteTodo}>Delete</button>
</li>
);
}
}
export default ToDo; //the component is made to export the data
App.js (for full code: https://jsfiddle.net/apjc6gk4/)
[...]
deleteTodo() {
console.log("to do deleted");
}
[...]
You need pass deleteTodo to ToDo comoponent
<ToDo key={ index }
deleteTodo={this.deleteTodo.bind(this)}
description={ todo.description }
isCompleted={ todo.isCompleted }
toggleComplete={ () => this.toggleComplete(index)}
isDeleted={todo.isDeleted}/>
You are not passing deleteTodo method as prop to Todo component
<ToDo key={ index } description={ todo.description } isCompleted={ todo.isCompleted } toggleComplete={ () => this.toggleComplete(index)} isDeleted = {todo.isDeleted}/>
Pass this method as prop to Todo component, and then call it
<ToDo key={ index } description={ todo.description } isCompleted={ todo.isCompleted } toggleComplete={ () => this.toggleComplete(index)} isDeleted = {todo.isDeleted} deleteTodo={this.deleteTodo.bind(this)}/>
In my case, following steps help me same as your case.
I hope to help you with my steps.
Define function in parent component to receive props from child component.
In parent component, pass function name to child component by props.
In child component, call props function when button clicked.
You can see result in the parent component from child.
I have imported a component from a different file and I want to reset my timer if I click on the imported component's elements. Is there a way to tackle this issue or should I write both components in single jsx ?
import {SampleComponent} from "../SampleComponent";
<div>
<SampleComponent onClick = {?????????}/>
</div>
What you can do here is,
import {SampleComponent} from "../SampleComponent";
<div onClick={??????}>
<SampleComponent/>
</div>
Or you can pass the function from your parent component and add click event on top node of the child component.
<div>
<SampleComponent onHandleClick={() => ??????}/>
</div>
If you want to call a function in parent component, whenever an event (such as in your case an onClick event) occurs in a child component, you will need to pass the parent function as a props.
Here's what it will look like:
class ParentComponent extends React.Component {
handleClick = () => { ... }
render {
return (
<SampleComponent onClick={this.handleClick} />
)
}
}
And here is how your SampleComponent will be:
class SampleComponent extends React.Component {
render {
return (
<div onClick={this.props.onClick}> //to call the function on whole component
<button onClick={this.props.onClick}>Click Me</button> //to call the function on a specific element
</div>
)
}
}
What I have understand so far from your question is that you want to call a function in SampleComponent whenever a click event occurs on it (on SampleComponent).
To do this, here is how your SampleComponent will look like :
class SampleComponent extends React.Component {
.
.
render() {
handleClick = () => { ... }
return (
<div onClick={this.handleClick}>
...
</div>
)
}
Note: For this you don't need to add onClick in parent.
resetTimerHandler = (timer)=>{
timer = 0; or this.setState({timer: 0}) // how ever you are defining timer
}
render(){
let displayTimer;
this.updateTimer(displayTimer)// However you are updating timer
return(
<SampleComponent onClick={this.resetTimerHandler.bind(this,displayTimer)} />)
Without knowing how you are updating your timer I can't really give a specific answer but you should be able to apply this dummy code.
It's hard to answer your question specifically without more context (like what timer are you wanting to reset). But the answer is no, you do not need to implement both components in the same file. This is fundamental to react to pass props like what you tried to do in your question.
Here is an example.
Say your SampleComponent looks like the following:
// SampleComponent.jsx
function SampleComponent({ onClick }) { // the argument is an object full of the props being passed in
return (
<button onClick={(event) => onClick(event)}>Click Me!</button>
);
}
and the component that is using SampleComponent looks like this:
import SampleComponent from '../SampleComponent';
function resetTimer() {
// Add logic to reset timer here
}
function TimerHandler() {
return (
<SampleComponent onClick={() => resetTimer()} />
);
}
Now when you click the button rendered by SampleComponent, the onClick handler passed from TimerHandler will be called.
A prop on a React component is really just an argument passed into a function :)
(this question differs to 'is it possible to use a component inside another', this question is 'can I define a component inside the definition of another', it is not a duplicate of 'Can I write Component inside Component in React?')
Is it possible to define a component inside the definition of another component? This way I can use the props of the outside component in the inner component. It would keep the code more concise. Something like the following...
class AComponent extends Component {
CustomButton = (props) => {
let { disabled, ...otherProps } = props // <-- props of the inner component
const {isDisabled, currentClassName} = this.props // <-- props of the main component
return (
<button
className={className}
disabled={isDisabled}
{...otherProps}>
</button>
)
}
render() {
return (
<div>
<CustomButton>Add something</CustomButton>
<CustomButton>Delete something</CustomButton>
<CustomButton>Edit</CustomButton>
</div>
)
}
}
If the custom button was defined on its own (the usual way of defining components) I would have to do something like below which is ok but more verbose and less dry as I repeat the definition of {...buttonProps} for each component
let buttonProps = {
className: this.props.currentClassName,
disabled: this.props.disabled
}
return (
<div>
<button {...buttonProps}>Add something</button>
<button {...buttonProps}>Delete something</button>
<button {...buttonProps}>Edit</button>
</div>
)
While yes, it's possible to define one function component inside another function component, this is not recommended.
Referring to the ReactJs docs:
reactjs.org/docs/components-and-props
reactjs.org/docs/conditional-rendering
Most, if not all, examples show child components being defined outside of the parent component.
Defining a component inside another will cause the child component to be re-created on mount and unmount of the parent, which could cause unexpected behavior if the child is using props from the parent, and cannot handle if those props are suddenly undefined.
It's best to define components separately.
Yes! I needed to define the function component in the render method...which makes sense
class AComponent extends Component {
render() {
const ButtonLocal = (props) => {
const {isDisabled, currentClassName} = this.props
return (
<Button
disabled={isDisabled}
className={currentClassName}
{...buttonProps}>
</Button>
)
}
return (
<div>
<ButtonLocal>Add something</ButtonLocal>
<ButtonLocal>Delete something</ButtonLocal>
<ButtonLocal>Edit</ButtonLocal>
</div>
)
}
}
Very much possible to add components inside a parent component. Consider following example:
<ParentComponent style={styles}>
<ChildComponent style={styles} {...props} />
</ParentComponent>
I have a piece of code
import React, {Component} from 'react';
class App extends Component {
render() {
return (
<Container>
<Child/>
</Container>
)
}
}
class Container extends Component {
render() {
console.log('Container render');
return (
<div onClick={() => this.setState({})}>
{this.props.children}
</div>
)
}
}
class Child extends Component {
render() {
console.log('Child render');
return <h1>Hi</h1>
}
}
export default App;
When clicking on 'Hi' msg, only Container component keeps re-rendering but Child component is not re-rendered.
Why is Child component not re-rendered on Container state change?
I would reason, that it doesn't happen due to it being a property of Container component, but still this.props.child is evaluated to a Child component in JSX, so not sure.
<div onClick={() => this.setState({})}>
{this.props.children}
</div>
Full example https://codesandbox.io/s/529lq0rv2n (check console log)
The question is quite old, but since you didn't seem to get a satisfying answer I'll give it a shot too.
As you have observed by yourself, changing
// Scenario A
<div onClick={() => this.setState({})}>
{this.props.children}
</div>
to
// Scenario B
<div onClick={() => this.setState({})}>
<Child />
</div>
will in fact, end up with
Container render
Child render
in the console, every time you click.
Now, to quote you
As fas as I understand, if setState() is triggered, render function of
Container component is called and all child elements should be
re-rendered.
You seemed to be very close to understanding what is happening here.
So far, you are correct, since the Container's render is executed, so must the components returned from it call their own render methods.
Now, as you also said, correctly,
<Child />
// is equal to
React.createElement(Child, {/*props*/}, /*children*/)
In essence, what you get from the above is just an object describing what to show on the screen, a React Element.
The key here is to understand when the React.createElement(Child, {/*props*/}, /*children*/) execution happened, in each of the scenarios above.
So let's see what is happening:
class App extends Component {
render() {
return (
<Container>
<Child/>
</Container>
)
}
}
class Container extends Component {
render() {
console.log('Container render');
return (
<div onClick={() => this.setState({})}>
{this.props.children}
</div>
)
}
}
class Child extends Component {
render() {
console.log('Child render');
return <h1>Hi</h1>
}
}
You can rewrite the return value of App like this:
<Container>
<Child/>
</Container>
// is equal to
React.createElement(
Container,
{},
React.createElement(
Child,
{},
{}
)
)
// which is equal to a React Element object, something like
{
type: Container,
props: {
children: {
type: Child, // |
props: {}, // +---> Take note of this object here
children: {} // |
}
}
}
And you can also rewrite the return value of Container like this:
<div onClick={() => this.setState({})}>
{this.props.children}
</div>
// is equal to
React.createElement(
'div',
{onClick: () => this.setState({})},
this.props.children
)
// which is equal to React Element
{
type: 'div',
props: {
children: this.props.children
}
}
Now, this.props.children is the same thing as the one included in the App's returned React Element:
{
type: Child,
props: {},
children: {}
}
And to be exact, these two things are referentially the same, meaning it's the exact same thing in memory, in both cases.
Now, no matter how many times Container get's re-rendered, since its children are always referentially the same thing between renders (because that React Element was created in the App level and it has no reason to change), they don't get re-rendered.
In short, React doesn't bother to render a React Element again if it is referentially (===) equal to what it was in the previous render.
Now, if you were to change the Container you would have:
<div onClick={() => this.setState({})}>
<Child />
</div>
// is equal to
React.createElement(
'div',
{onClick: () => this.setState({})},
React.createElement(
Child,
{},
{}
)
)
// which is equal to
{
type: 'div',
props: {
children: {
type: Child,
props: {},
children: {}
}
}
}
However in this case, if you were to re-render Container, it will have to re-execute
React.createElement(
Child,
{},
{}
)
for every render. This will result in React Elements that are referentially different between renders, so React will actually re-render the Child component as well, even though the end result will be the same.
Reference
The <Child /> component is not re-rendered because the props have not changed. React uses the concept of Virtual DOM which is a representation of your components and their data.
If the props of a component do not change the component is not re-rendered. This is what keeps React fast.
In you example there are no props sent down to Child, so it will never be re-rendered. If you want it to re-render each time (why would you ?), you can for example use a pure function
const Child = () => <h1>Hi</h1>;
Change {this.props.children} to <Child /> in Container component, (now you can remove <Child /> from App component).
If you are clicking the div you will get both the 'Child render' and 'Container render' in console.
(In this example your child is static component. Then there is no point for the re-rendering.)
I have a component whose state is passed as a prop to a child component. I noticed that even if the Parent's state is changed, the child component is not re-rendered.
Based on the official React Documentation for utilizing shouldComponentUpdate:
"The first time the inner component gets rendered, it will have { foo:
'bar' } as the value prop. If the user clicks on the anchor, the
parent component's state will get updated to { value: { foo: 'barbar'
} }, triggering the re-rendering process of the inner component, which
will receive { foo: 'barbar' } as the new value for the prop.
The problem is that since the parent and inner components share a
reference to the same object, when the object gets mutated on line 2
of the onClick function, the prop the inner component had will change.
So, when the re-rendering process starts, and shouldComponentUpdate
gets invoked, this.props.value.foo will be equal to
nextProps.value.foo, because in fact, this.props.value references the
same object as nextProps.value.
Consequently, since we'll miss the change on the prop and short
circuit the re-rendering process, the UI won't get updated from 'bar'
to 'barbar'."
If I can't use shouldComponentUpdate, how would I force the child component to re-render based on a change of props from the Parent?
Parent Component
I want the child component to rerender based on the boolean given to showDropzone.
<Dropzone
onDrop={this.onDrop}
clearFile = {this.clearFile}
showDropzone = {this.state.filePresent}/>
Child Component
export default class Dropzone extends Component {
constructor(props) {
super(props);
}
render() {
const { onDrop } = this.props;
const {showDropzone} = this.props;
const {clearFile} = this.props;
return (
<div className="file-adder">
<div className="preview">
{{showDropzone}?
<Dropzone
onDrop={onDrop}
ref="dropzone">
</Dropzone>
:<button type="button"
className="btn btn-primary"
onClick={clearFile}>
Clear File</button>}
</div>
</div>
);
}
}
I'am sorry but your code has a lot of errors
First (This is a tip) inside:
const { onDrop } = this.props;
const { showDropzone } = this.props;
const { clearFile } = this.props;
You can write just one line
const { onDrop, showDropzone, clearFile } = this.props;
Now your problems starts from here:
You used showDropzone inside curly brackets and this is your
problem remove them
Your mistake {{showDropzone}? firstOption : anotherOption }
Will be { showDropzone? firstOption : anotherOption }
Another mistake:
You used the Dropzone component inside itself and this is a big mistake
You can't use Dropzone component here {{showDropzone}? <Dropzone {...}/> : anotherOption } You can use it from another component
Finally i tried to format your code to make it like this
Parent Component
{ this.state.filePresent
? <Dropzone onDrop={this.onDrop} />
: <button
type="button"
className="btn btn-primary"
onClick={clearFile}
children="Clear File"
/>
}
Child Compnent
class Dropzone extends Component {
render() {
const { onDrop } = this.props;
return (
<div className="file-adder">
<div className="preview" onDrop={onDrop} ref="dropzone">
<p>Hi! This is Dropzone component</p>
</div>
</div>
);
}
}
export default Dropzone;
In child component you have used "showZone" instead of "showDropzone".
Thanks