Develop Reference

Troubles with state

I'm just started to learn react, and i have a question
Well, i can impact on state from one component to another. But can i do it in reverse?
Here's what i mean:
import React from 'react';
import Butt from './Button';
class Checkbox extends React.Component {
constructor(props) {
super();
}
render() {
return (
<div>
<Butt arg={13} />
</div>
);
}
}
export default Checkbox;
import React from 'react';
class Butt extends React.Component {
constructor(props) {
super();
this.state = {
s1: props.arg,
};
}
add = () => {
let val = this.state.s1;
val++;
this.setState({ s1: val });
};
render() {
return (
<div>
<label>
<label>
<button onClick={this.add}>add</button>
<div>{this.state.s1}</div>
</label>
</label>
</div>
);
}
}
export default Butt;
Sorry for my silly question. Thanks in advance :)

I am not sure about your question, but in react, there is a one-way flow (from parent to child) for transferring information (props, states, or ...). If you want to have access to states everywhere or set them in each direction you should use Redux or context or any other state management.

You're updating the Butt state from inside Butt so this will work fine. It won't change the value of this.props.arg though, if that's what you're asking.
Props are always non-mutable.
What you can do is have two components share the state of their parent...
class Parent extends React.Component {
state = {
val = 0
}
render () {
return (
<>
<Child1
val={this.state.val}
onChange={newVal => this.setState({ val: newVal })}
/>
<Child2
val={this.state.val}
onChange={newVal => this.setState({ val: newVal })}
/>
</>
)
}
}
Then inside the child components pass the updated value to onChange...
class Child1 extends React.Component {
handleChange() {
this.props.onChange(this.props.val + 1)
}
render() {
return (
<Button onClick={() => this.handleChange()}>
Update value
</Button>
)
}
}
This way you're just passing a new value from Child to Parent and letting Parent decide what to do with it.
Whether Child1 or Child2 sends the new value, both children will get updated when Parent calls this.setState({ val: newVal }) and changes this.state.val.

Cannot update the app state from custom component using React and Redux

I have the following Codesandbox.io:
https://codesandbox.io/s/qxkq5vvm1q
which is a basic ReactJS / Redux application.
The key components here are:
a Select which gets its values something like through this way: Redux (state manager) -> PanelMaterialSize (container) -> Select
one Updater component which takes care of update the values available on the Select through Redux
Alert button, which when clicked should alert the value stored on the store
What should happen is:
when the user changes an option on the Select, that value should be stored on the store. This is actually happening properly - OK
if the Select gets its values changed (for example because the Updater component), then it should automatically change the value stored on the store with the value it is showing (something similar as if the user changes the value on it). Unfortunately this is not happening - The Goal
Here are some of the codes:
./src/controls/Select/Select.js
import React, { Component } from "react";
import "./Select.scss";
class Select extends Component {
constructor(props) {
super(props);
let { name, data, className, ...controlProps } = this.props;
this.name = name;
this.data = data;
this.controlProps = controlProps;
this.state = {
[name]: data,
className
};
}
render() {
let data = this.state[this.name];
return (
<div className="control-select" {...this.controlProps}>
<div className="custom-dropdown custom-dropdown--grey">
<select className="custom-dropdown__select custom-dropdown__select--grey">
{this.props.data.length > 0 &&
this.props.data.map((elem, index) => {
return (
<option value={elem.value} key={index}>
{elem.text}
</option>
);
})}
</select>
</div>
</div>
);
}
}
export default Select;
src/controls/PanelMaterialSize/PanelMaterialSize.js
import React, { Component } from "react";
import { connect } from "react-redux";
import "./PanelMaterialSize.scss";
import Select from "../Select/Select";
import { setThemeList, setSelectedTheme } from "../../store/AppConfig/actions";
class PanelMaterialSize extends Component {
constructor(props) {
super(props);
this.state = {
selection: "",
options: []
};
}
handleChange = e => {
let target = e.target;
let value = target.value;
this.props.setSelectedTheme(value);
};
render() {
return (
<div className="partial-designer-panel-material-size">
<div>
<div className="label-input">
<div className="label">THEME</div>
<div className="input">
<Select
name="selection"
value={this.state.selection}
data={this.props.themeList}
style={{ width: "100%" }}
onChange={this.handleChange}
/>
</div>
</div>
</div>
</div>
);
}
}
const mapStateToProps = appState => {
return {
themeList: appState.appConfig.themeList,
selectedTheme: appState.appConfig.selectedTheme,
};
};
const mapDispatchToProps = dispatch => {
return {
setThemeList: themeList => dispatch(setThemeList(themeList)),
setSelectedTheme: selectedTheme => dispatch(setSelectedTheme(selectedTheme)),
};
};
export default connect(
mapStateToProps,
mapDispatchToProps
)(PanelMaterialSize);
Any idea on how to make the point 2 work?
If possible, please, provide back your solution on a forked Codesandbox.io.
Thanks!

Updater component is producing new list of themes every 3seconds
It must also dispatch setSelectedTheme action to update selected theme in application state

ReactJS instant Search with input

Im making my first react project. Im new in JS, HTML, CSS and even web app programming.
What i want to do it is a Search input label. Now its look like this:
Like you can see i have some list of objects and text input.
I Have two components, my ProjectList.js with Search.js component...
class ProjectsList extends Component {
render() {
return (
<div>
<Search projects={this.props.projects} />
<ListGroup>
{this.props.projects.map(project => {
return <Project project={project} key={project.id} />;
})}
</ListGroup>
</div>
);
}
}
export default ProjectsList;
... and ProjectList.js displays Project.js:
How looks Search.js (its not ended component)
class Search extends Component {
state = {
query: ""
};
handleInputChange = () => {
this.setState({
query: this.search.value
});
};
render() {
return (
<form>
<input
ref={input => (this.search = input)}
onChange={this.handleInputChange}
/>
<p />
</form>
);
}
}
export default Search;
My project have name property. Could you tell me how to code Search.js component poperly, to change displaying projects dynamically based on input in text label? for example, return Project only, if text from input match (i want to search it dynamically, when i start typing m... it shows all projects started on m etc).
How to make that Search input properly? How to make it to be universal, for example to Search in another list of objects? And how to get input from Search back to Parent component?
For now, in react dev tools whatever i type there i get length: 0
Thanks for any advices!
EDIT:
If needed, my Project.js component:
class Project extends Component {
state = {
showDetails: false
};
constructor(props) {
super(props);
this.state = {
showDetails: false
};
}
toggleShowProjects = () => {
this.setState(prevState => ({
showDetails: !prevState.showDetails
}));
};
render() {
return (
<ButtonToolbar>
<ListGroupItem className="spread">
{this.props.project.name}
</ListGroupItem>
<Button onClick={this.toggleShowProjects} bsStyle="primary">
Details
</Button>
{this.state.showDetails && (
<ProjectDetails project={this.props.project} />
)}
</ButtonToolbar>
);
}
}
export default Project;

To create a "generic" search box, perhaps you could do something like the following:
class Search extends React.Component {
componentDidMount() {
const { projects, filterProject, onUpdateProjects } = this.props;
onUpdateProjects(projects);
}
handleInputChange = (event) => {
const query = event.currentTarget.value;
const { projects, filterProject, onUpdateProjects } = this.props;
const filteredProjects = projects.filter(project => !query || filterProject(query, project));
onUpdateProjects(filteredProjects);
};
render() {
return (
<form>
<input onChange={this.handleInputChange} />
</form>
);
}
}
This revised version of Search takes some additional props which allows it to be reused as required. In addition to the projects prop, you also pass filterProject and onUpdateProjects callbacks which are provided by calling code. The filterProject callback allows you to provide custom filtering logic for each <Search/> component rendered. The onUpdateProjects callback basically returns the "filtered list" of projects, suitable for rendering in the parent component (ie <ProjectList/>).
The only other significant change here is the addition of visibleProjects to the state of <ProjectList/> which tracks the visible (ie filtered) projects from the original list of projects passed to <ProjectList/>:
class Project extends React.Component {
render() {
return (
<div>{ this.props.project }</div>
);
}
}
class ProjectsList extends React.Component {
componentWillMount() {
this.setState({ visibleProjects : [] })
}
render() {
return (
<div>
<Search projects={this.props.projects} filterProject={ (query,project) => (project == query) } onUpdateProjects={ projects => this.setState({ visibleProjects : projects }) } />
<div>
{this.state.visibleProjects.map(project => {
return <Project project={project} key={project.id} />;
})}
</div>
</div>
);
}
}
class Search extends React.Component {
componentDidMount() {
const { projects, filterProject, onUpdateProjects } = this.props;
onUpdateProjects(projects);
}
handleInputChange = (event) => {
const query = event.currentTarget.value;
const { projects, filterProject, onUpdateProjects } = this.props;
const filteredProjects = projects.filter(project => !query || filterProject(query, project));
onUpdateProjects(filteredProjects);
};
render() {
return (
<form>
<input onChange={this.handleInputChange} />
</form>
);
}
}
ReactDOM.render(
<ProjectsList projects={[0,1,2,3]} />,
document.getElementById('react')
);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.0.0/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.0.0/umd/react-dom.production.min.js"></script>
<div id="react"></div>

I will assumes both your Search and ProjectList component have a common parent that contains the list of your projects.
If so, you should pass a function into your Search component props, your Search component will then call this function when the user typed something in the search bar. This will help your parent element decide what your ProjectsLists needs to render :
handleInputChange = () => {
this.props.userSearchInput(this.search.value);
this.setState({
query: this.search.value
});
};
And now, here is what the parent element needs to include :
searchChanged = searchString => {
const filteredProjects = this.state.projects.filter(project => project.name.includes(searchString))
this.setState({ filteredProjects })
}
With this function, you will filter out the projects that includes the string the user typed in their names, you will then only need to put this array in your state and pass it to your ProjectsList component props
You can find the documentation of the String includes function here
You can now add this function to the props of your Search component when creating it :
<Search userSearchInput={searchChanged}/>
And pass the filtered array into your ProjectsList props :
<ProjectsList projects={this.state.filteredProjects}/>
Side note : Try to avoid using refs, the onCHnage function will send an "event" object to your function, containing everything about what the user typed :
handleInputChange = event => {
const { value } = event.target
this.props.userSearchInput(value);
this.setState({
query: value
});
};
You can now remove the ref from your code

Updating state in react js

I have this code that renders a dropdown component from material ui and it's populated with data coming from a WS.
I set an initial value that is the firs element coming from the WS so when I render the page for the first time I can see the correct value in the dropdown.
My issue is when I try to select a different value on the dropdown, I'm not able to do it and I think is because I'm not updating the state, I have a method called "handleChange" but I'm missing something there but don't know what.
This is the code and hope someone can help with this, I'm new to react and still to practice much more.
import React, { Component } from 'react';
import DropDownMenu from 'material-ui/DropDownMenu';
import MenuItem from 'material-ui/MenuItem';
export default class WebserviceTest extends Component {
constructor() {
super();
this.state = {
data: [],
selected: ''
};
this.renderOptions = this.renderOptions.bind(this);
this.handleChange = this.handleChange.bind(this);
}
componentDidMount() {
const url = 'https://randomuser.me/api/?results=4';
fetch(url)
.then(Response => Response.json())
.then(findResponse => {
console.log(findResponse);
this.setState({
data: findResponse.results,
selected: findResponse.results[0].name.first
});
console.log('----- ', this.setState.selected);
});
}
handleChange(value) {
this.setState({ selected: (value) });
}
renderOptions() {
return this.state.data.map((dt, i) => {
return (
<MenuItem
key={i}
value={dt.name.first}
primaryText={dt.name.first} />
);
});
}
render() {
return (
<div>
<DropDownMenu value={this.state.selected} onChange={this.handleChange}>
{this.renderOptions()}
</DropDownMenu>
</div>
);
}
}
Any help will be very welcome!
Thanks in advance..

In material UI dropdown, the selected value appears as third argument. So use something like this for your handleChange method
handleChange(event, index, value) {
this.setState({ selected: (value) });
}
Ref: http://www.material-ui.com/#/components/dropdown-menu#properties

Programmatically open a route with state in react

I have two types of item, one of which can contain data similar to the other.
Currently when form is used to save an item it saves it then uses browserHistory.push to show the next page.
But I wish add a button that will
save the currently item
redirect them to the form to add the other item type,
partially fill out this form with the data from the first item.
Is there a way to do this using react and not using local storage or session variables?

You should take a look to Redux (or other Flux based libraries) to store data between components and routes, avoiding the excessive prop nesting.

browserHistory.push won't work. It only moves you to a certain location but it doesn't update the application state. You need to update application state, which then will reflect into location update, but not in the opposite direction. Keep in mind that, in React, data comes first, and its representation, even though mutable, doesn't change the data back. The same applies to the location.
To make the redirect alone work, I'd recommend wrapping your component into withRouter higher-order component.
import React, { Component } from 'react';
import { withRouter } from 'react-router';
class MyComponent extends Component {
render() {
return (
<div>
<button
onClick={() => this.props.router.push('/new-location')}>
Click me to go to /new-location
</button>
</div>
);
}
}
But if you need to pass data from one component to another, and the two aren't in hierarchy, I'd agree with Alomsimoy and recommend using Redux. But if, for some reason, it's not an option, you can store this data in a component that is parent to both forms:
class FormA extends Component {
render() {
return (
<form onSubmit={() => this.props.onSubmit()}>
<input
type="text"
value={this.props.inputA}
onChange={(event) => this.props.handleChangeA(event)} />
</form>
);
}
}
class FormB extends Component {
render() {
return (
<form onSubmit={() => this.props.onSubmit()}>
<input
type="text"
value={this.props.inputB}
onChange={(event) => this.props.handleChangeB(event)} />
</form>
);
}
}
while their parent would rule the location and state updates:
class Forms extends Component {
constructor() {
super();
this.state = {};
}
handleChange(name, value) {
this.setState({
[name]: value
});
}
renderForm() {
const {
params: {
stepId
}
} = this.props;
if (stepId === 'step-a') { // <- will be returned for location /form/step-a
return (
<FormA
inputA={this.state.inputA}
handleChangeA={(event) => this.handleChange('inputA', event.target.value)}
onSubmit={() => this.props.router.push('/form/step-b')} />
);
} else if (stepId === 'step-b') { // <- will be returned for location /form/step-b
return (
<FormB
inputB={this.state.inputB}
handleChangeB={{(event) => this.handleChange('inputA', event.target.value)} />
);
}
}
render() {
const {
children
} = this.props;
console.log(this.state); // track changes
return (
<div>
{this.renderForm()}
<button
onClick={() => this.props.router.push('/new-location')}>
Click me to go to /new-location
</button>
</div>
);
}
}
export default withRouter(Forms);
so the route for them would look like
<Route path="form/:stepId" component={Forms} />