React Redux - pass data down to components via props or connect - reactjs

I'm working on React Redux app and I have quite fundamental question about some kind of best practises.
I have MainComponent (kind of container) where I'm fetching data on componentDidMount:
class MainComponent extends React.Component {
componentDidMount(){
this.fetchData()
}
fetchData() {
this.props.fetchDataAction()
}
render() {
return (
<div>
<ChildComponent1 />
<ChildComponent2 />
</div>
)
}
}
export default connect(mapStateToProps,{fetchDataAction})(MainComponent)
How to pass fetched data to ChildComponents? What is the best practise? Two possible solutions are (IMHO - maybe more?)
First solution:
class MainComponent extends React.Component {
...
render() {
return (
<div>
<ChildComponent1 dataOne={this.props.data.one} />
<ChildComponent2 dataTwo={this.props.data.two} />
</div>
)
}
...
Second solution - connect ChildComponents to store which is updated by fetchDataAction() in MainComponent:
class ChildComponent1 extends React.Component {
render() {
return (
<div>
{this.props.one}
</div>
)
}
}
function mapStateToProps(state){
return (
one: state.one
)
}
export default connect(mapStateToProps,null)(ChildComponent1)
Now I use first solution when ChildComponents do not fire actions which update store and second solution when they do. But I'm not sure if it is proper approach.

If you have multiple child components and you have to pass a part of fetched data to different child components ; I would suggest keep the parent component as single point of source.
You can try something like:-
class MainComponent extends React.Component {
constructor(){
super()
this.state = {
data : {}
}
}
componentDidMount(){
this.fetchData()
}
fetchData() {
this.props.fetchDataAction()
}
componentWillReceiveProps(nextProps){
//once your data is fetched your nextProps would be updated
if(nextProps.data != this.props.data && nextProps.data.length>0){
//sets your state with you data--> render is called again
this.setState({data:nextProps.data})
}
render() {
//return null if not data
if(this.state.data.length === 0){
return null
}
return (
// it should have keys as one and two in api response
<div>
<ChildComponent1 data={data.one}/>
<ChildComponent2 data={data.two}/>
</div>
)
}
}
function mapStateToProps(state){
return (
data: state
)
}
export default connect(mapStateToProps,{fetchDataAction})(MainComponent)
I feel all logic stays at one place this way. Say if you plan to add to add few more child components in future,you only need to add a line of code above and few changes in API. However if you read in each component you have connect that component to store again which makes it more complex.
So if you dont have any other logic in your child components apart from getting data I would keeping this logic in the parent component.

Related

How do I implement an onClick method in one child component that updates the text in a sibling component, based on the state in App.js?

Every row in my SideMenuContainer corresponds to an object from schema.json, showing only the name property. The behavior I want is that when a row is clicked, the PaneViewContainer toggles to display the name and other properties of that respective object from the json.
In App.js, the data is passed to SideMenuContainer like so:
render() {
return (
<MainContainer>
<SideMenuContainer genInfoList={this.state.genInfoList}/>
<PaneViewContainer genInfoList={this.state.genInfoList}/>
</MainContainer>
);
}
In SideMenuContainer, every row is populated like this:
render() {
return (
<SideMenuPane>
<SideMenu>
<div>
<h2>GenInfo</h2>
{this.props.genInfoList.map(genInfoElement => {
return (
<SideMenuRow>
{genInfoElement.name}
</SideMenuRow>
);
})}
</div>
</SideMenu>
</SideMenuPane>
);
}
What I want to do is change the genInfoList information being displayed in the PaneViewContainer based on which row is clicked in its sibling, SideMenuContainer.
The entire genInfoList data is being passed to both sibling components from their parent App.js, so I want to change which portion of that data is loaded in the Pane based on the row clicked in the SideMenu.
I thought about using the Context API, but I'm having trouble figuring out how to implement it for this purpose. Any ideas?
If I understand correctly you have your information stored in the parent element of both components then you can just pass a function down as a prop and have all of your logic stored in the parent element.
changeInfoList = id => {
//change your info list based on id or index or whatever
this.setState({
//your new list
})
}
render() {
return (
<MainContainer>
<SideMenuContainer changeInfoList={this.changeInfoList} genInfoList={this.state.genInfoList}/>
<PaneViewContainer genInfoList={this.state.genInfoList}/>
</MainContainer>
);
}
and then call changeInfoList from your component with props
render() {
return (
<SideMenuPane>
<SideMenu>
<div>
<h2>GenInfo</h2>
{this.props.genInfoList.map(genInfoElement => {
return (
<SideMenuRow>
{genInfoElement.name}
<button onClick={this.props.changeInfoList(genInfoElement.id)>CLick Me</button>
</SideMenuRow>
);
})}
</div>
</SideMenu>
</SideMenuPane>
);
}
this is commonplace in react as you should have smart components and dumb components. When you have components not in the same tree or spread far away then the context api is very useful. In your case I don't think its necessary.
Without external state management, you would have to pass down a callback (as props), so the children can update the parent's state.
As the components get far away from each other, this pattern can get annoying (passing down callbacks each time). That's where external state management can help.
Here's a simple (and untested) example using a callback:
class Counter extends React.Component {
constructor() {
super();
this.increment = this.increment.bind(this);
this.state = {count: 0};
}
increment() {
let count = thist.state.count;
this.setState({count: count + 1});
}
render() {
return <div>
<CounterButton increment={this.increment}/>
<CounterDisplay count={this.state.count}/>
</div>;
}
}
class CounterButton extends React.Component {
render() {
let increment = this.props.increment;
return <button onClick={increment}>Plus One</button>;
}
}
class CounterDisplay extends React.Component {
render() {
let count = this.props.count;
return <span>{count}</span>;
}
}

Reactjs coding with parent and child component

I have 3 components, that is 2 child components and one parent component.
I wanted to pass the child component value to parent (only the values not the components enitirely,it should not visible in parent) and this values from parent to another child component.
Any suggestions or logic of how to proceed on this, since I don't have any guidance as of right now I had to ask here. Is the above problem possible.
The code is very complex, so I have not put here.
Thank you
When you say values, do you mean state, props, user input, something else?
If you mean state or props: React has a 1-way data flow, so the easiest way to accomplish this is to actually store the data at a higher level. Either store the data used by the child in the parent and pass it down to the children for consumption, or else use a store that both parent and children have access to. Either way, this will make it much easier for all components to access the data.
If you mean user input: one way you can accomplish this is to pass a callback from the parent component to the child as a prop, and then in the child call that callback when a user does something or changes some value. The callback function can make the data accessible to the parent on that user action, and then you can decide what to do with the data from there.
AksharaDL,
Child to Parent — Use a callback and states
Parent to Child — Use Prop
Also here is another article explaining it: https://medium.com/#ruthmpardee/passing-data-between-react-components-103ad82ebd17
here is the solution.
in parrent component you have a state. and have a setData method to update state. pass setData to ChildOne use props. and data to ChilTwo and use it
class StoreBanner extends React.Component {
constructor() {
this.state = {
data: 'whatever'
}
}
setData = (data) => {
this.setState({data})
}
render() {
return (
<div>
<ChildOne setData={this.setData}/>
<ChildTwo data={this.state.data}/>
</div>
)
}
}
and in ChildOne you can update the parrent state
class ChildOne extends React.Component {
setParentData = () => {
this.props.setData('another')
}
...
}
You can do it like this.
class ParentComp extends React.Component {
constructor() {
super();
this.state = {
theStateToPass: null
}
this.receiveDataFromChild = this.receiveDataFromChild.bind(this);
}
receiveDataFromChild(data) {
this.setState({
theStateToPass: data
})
}
render() {
return (
<div>
<FirstChild updateMe={this.receiveDataFromChild} />
<SecondChild stateFromFirstChild={this.state.theStateToPass} />
</div>
)
}
}
class FirstChild extends React.Component {
constructor(props) {
super(props);
this.callParentMethod = this.callParentMethod.bind(this);
}
callParentMethod(e) {
let someDataToSend = "ABC";
this.props.updateMe(someDataToSend)
}
render() {
return (
<div onClick={this.callParentMethod}>
</div>
)
}
}
class SecondChild extends React.Component {
render() {
return (
<div>
{this.props.stateFromFirstChild}
</div>
)
}
}
however it becomes complex and might lead to one's pulling their hair out. so i would suggest using redux , it keeps the flow simple , you have a reducer , actions and a container. everything goes with a flow and keeps it clean but it does comes with an extra overhead of more code as you will be creating container reducer and actions.

React handle state update

I'm using the react to build some input forms.
While all children inputs have and their own states to store values I have no idea how to process the to a parent.
Here's example:
class FormComponent extends Component {
constructor(props) {
super(props);
this.state = {
title: null,
someAmount: null
}
}
render() {
let me = this;
return (
<div>
<TextField
value={me.state.title}
onChange={(proxy, value) => {
me.setState({title: value})
me.hanleChnage();
}
}
/>
<TextField
value={Number.parseFloat(me.state.someAmount)}
onChange={(proxy, value) => {
if (!isNaN(Number.parseFloat(value))) {
me.setState({someAmount: value})
me.hanleChnage();
}
}
}
/>
</div>
)
}
handleChange() {
//Calling the parent
//State here is outdated
this.props.onUpdate && this.props.onUpdate(this.state);
}
}
export default FormComponent;
Or where I can find some example of usage of compex forms with much inputs in react.
Thanks!
Sounds like you need to consider moving some of your state into the parent components. The React docs have a good article about this.
To summarize, you can pass your hanleChnage(); function as a prop to your child components if you declare the function in your parent.
function handleChange() { //do something... }
...
<ChildComponent parentOnChange={this.handleChange.bind(this) />
As your components grow in complexity, you might consider using Redux for state management, thus serving as a single source for all state in your application.
Set a child property, (e.g. callParentProperty) to reference a function in the parent component (e.g. parentFunction).
class ParentComponent extends Component{
parentFunction(parameter) {
console.log("This is the form value");
console.log(parameter);
}
render() {
return <FormComponent callParentFunctionProperty={this.parentFunction.bind(this)} />
}
}
class FormComponent extends Component {
...
handleChange() {
...
let formValue = this.state.someAmount;
this.props.callParentFunctionProperty(formValue);
}
}

Update same variable from two different components

I want to use the same state variable say count and update and retrieve the updated one.
I wrote the following code as a higher order component consisting of one button and one label . Both updates the count but they have separate instances. So how can I re-align my code to keep the same copy of the variable count.
const HOC = (InnerComponent) => class extends React.Component{
constructor(){
super();
this.state = {
count: 0
}
}
update(){
this.setState({count: this.state.count + 1})
}
render(){
return(
<InnerComponent
{...this.props}
{...this.state}
update = {this.update.bind(this)}
/>
)
}
};
class App extends React.Component {
render() {
return (
<div>
<Button>Button</Button>
<hr />
<LabelHOC>Label</LabelHOC>
</div>
);
}
}
const Button = HOC((props) => <button onClick={props.update}>{props.children} - {props.count}</button>)
class Label extends React.Component{
render(){
return(
<label onMouseMove={this.props.update}>{this.props.children} - {this.props.count}</label>
)
}
}
const LabelHOC = HOC(Label)
export default App;
You need to do some "thinking-in-react".
React is just a rendering library, it renders the state, so you need to do some thinking about where that state should live. It's common for your scenario to start look at some sort of Flux library that can handle this "one source of truth" (keep you state in one place only), like Redux for example. If you're using Redux then the Redux store would hold the "count" state for both components and they could both update and read it, so that would be my suggestion in the long run. But to solve your immediate question, you must let a higher component hold the state and then of course also modify that state, you do that by passing down the state and a update function as props to the children.
This is snippet of how it could look, just send the state (count) and the update function down to the child components. I excluded HOC component because i think it just adds to your confusion here. But i'm sure you can imagine how it would work. :)
class App extends React.Component {
constructor(){
super();
this.state = {
count: 0
}
this.update = this.update.bind(this); //Bind it once
}
update(){
this.setState({count: this.state.count + 1})
}
render() {
return (
<div>
<Button count={this.state.count} update={this.update}>Button</Button>
<hr />
<LabelHOC count={this.state.count} update={this.update}>Label</LabelHOC>
</div>
);
}
}
Good reads from the docs:
Components and props
Data flows down

React.js - setState after calculation based on props

I have a component that receives images as props, performs some calculation on them, and as a result I need to update its class. But if I use setState after the calculation, I get the warning that I shouldn't update state yet... How should I restructure this?
class MyImageGallery extends React.Component {
//[Other React Code]
getImages() {
//Some calculation based on this.props.images, which is coming from the parent component
//NEED TO UPDATE STATE HERE?
}
//componentWillUpdate()? componentDidUpdate()? componentWillMount()? componentDidMount()? {
//I CAN ADD CLASS HERE USING REF, BUT THEN THE COMPONENT'S
// FIRST RENDERED WITHOUT THE CLASS AND IT'S ONLY ADDED LATER
}
render() {
return (
<div ref="galleryWrapper" className={GET FROM STATE????}
<ImageGallery
items={this.getImages()}
/>
</div>
);
} }
You should put your logic into componentWillReceiveProps (https://facebook.github.io/react/docs/component-specs.html#updating-componentwillreceiveprops) so as to do a prop transition before render occurs.
In the end what we did was run the logic in the constructor and then put the class into the initial state:
class MyImageGallery extends React.Component {
constructor(props) {
super(props);
this.getImages = this.getImages.bind(this);
this.images = this.getImages();
this.state = {smallImgsWidthClass: this.smallImgsWidthClass};
}
getImages() {
//Some calculation based on this.props.images, which is coming from the parent component
this.smallImgsWidthClass = '[calculation result]';
return this.props.images;
}
render() {
return (
<div className={this.state.smallImgsWidthClass }
<ImageGallery
items={this.images}
/>
</div>
);
}
}

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