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Change React component visibility based on the state of another component

I have created the following React component. It uses an input box to accept a user's answer to a riddle. As soon as the user's input matches the desired answer, the input box become read-only (a bit of a strange way to use them). It also has an "isHidden" prop to determine whether the riddle is rendered.
class Riddle extends React.Component {
constructor(props) {
super(props);
this.answer = props.answer.toUpperCase();
this.state = {
text: "",
isAnswered: false
};
this.handleChange = this.handleChange.bind(this);
}
handleChange(event) {
let userInput = event.target.value.toUpperCase();
if (userInput == this.answer) {
this.setState({
text: userInput,
isAnswered: true
});
} else {
this.setState({
text: userInput,
isAnswered: false
});
}
}
render() {
if (this.props.isHidden) {
return <div></div>;
} else {
return (
<div>
<p>{this.props.prompt}</p>
<input type="text" value={this.state.text}
readOnly={this.state.isAnswered}></input>
</div>
);
}
}
}
Here it is in practice:
function App() {
return (
<div>
<Riddle prompt='The first three letters in the alphabet.' answer="abc" isHidden="false"/>
</div>
);
}
ReactDOM.render(<App />, document.getElementById('root'));
What I would like to do is have a bunch of these riddles in sequence, but have riddles only be visible when the previous one was solved. The trouble is that I don't know how to cause the visibility update to happen.
I have read about lifting state from children to a parent component, and I've tried to see if I could create a RiddleSequence component with Riddles as its children, and have RiddleSequence manage visibility. My problem is that currently it is part of Riddle's state whether or not it's solved, and I don't know how RiddleSequence can read that information since child state should remain hidden. This seems like a reasonable way to encapsulate Riddle's functionality, but maybe I'm wrong given my goals.
I have also considered making Riddles be children of other riddles they depend on, since I can just pass state/props to children:
<Riddle prompt="first riddle"...>
<Riddle prompt="depends on first riddle"...>
<Riddle prompt="depends on second riddle"...>
</Riddle>
</Riddle>
</Riddle>
But if I have an app with 100 riddles, this seems to get ridiculous. This also reduces flexibility for a more expanded set of features (such as making one riddle depend on a group of 3 riddles).
How can I make the visibility of my Riddle components depend on the state of other riddles?

A simple solution would be to have a container component as you said:
class Riddle extends Component {
constructor(props) {
this.state = {
text: ''
}
this.answer = props.answer.toUpperCase()
}
handleChange = event => {
const userInput = event.target.value.toUpperCase()
const callback = userInput == this.answer ? this.props.onSolved : undefined
this.setState({ text: userInput }, callback)
}
render() {
const { text, isAnswered } = this.state
const { prompt } = this.props
if (this.props.isHidden) {
return null
}
return (
<div>
<p>{prompt}</p>
<input type="text" value={text} readOnly={isAnswered}></input>
</div>
)
}
}
and container should hold visibility like this:
class RiddleSequence extends Component {
state = {}
riddles = [
{
id: 1,
prompt: 'The first three letters in the alphabet.',
answer: 'abc',
prev: null
},
{
id: 2,
prompt: 'The last three letters in the alphabet.',
answer: 'xyz',
prev: 1
}
]
render() {
return (
<div>
{this.riddles.map(r => {
const { id, prev } = r
const visible = !prev || this.state[prev]
return (
<Riddle
key={id}
isHidden={!visible}
onSolved={() => this.setState({ [r.id]: true })}
{...r}
/>
)
})}
</div>
)
}
}

Loop over all instances of component, log each state

I'm building out a simple drum machine application using ReactJS and could use some help understanding how to loop through all instances of a component while outputting each instance's state.
The application UI shows 16 columns of buttons, each containing 4 unique drum rows. There is a "SixteenthNote.js" component which is essentially on column containing each "Drum.js" instance. In the "DrumMachine.js" module, I am outputting "SixteenthNote.js" 16 times to display one full measure of music. When you click on a drum button, that drum's value is pushed into the SixteenthNote' state array. This is all working as intended.
The last part of this is to create a "Play.js" component which, when clicked, will loop through all of the SixteenthNote instances and output each instance's state.
Here is the "DrumMachine.js" module
class DrumMachine extends Component {
constructor(props) {
super(props);
this.buildKit = this.buildColumns.bind(this);
this.buildLabels = this.buildLabels.bind(this);
this.buildAudio = this.buildAudio.bind(this);
this.state = {
placeArray: Array(16).fill(),
drumOptions: [
{type: 'crash', file: crash, title: 'Crash'},
{type: 'kick', file: kick, title: 'Kick'},
{type: 'snare', file: snare, title: 'Snare'},
{type: 'snare-2', file: snare2, title: 'Snare'}
]
}
}
buildLabels() {
const labelList = this.state.drumOptions.map((sound, index) => {
return <SoundLabel title={sound.title} className="drum__label" key={index} />
})
return labelList;
}
buildColumns() {
const buttonList = this.state.placeArray.map((object, index) => {
return <SixteenthNote columnClassName="drum__column" key={index} drumOptions={this.state.drumOptions}/>
});
return buttonList;
}
buildAudio() {
const audioList = this.state.drumOptions.map((audio, index) => {
return <Audio source={audio.file} drum={audio.type} key={index}/>
})
return audioList;
}
render() {
return (
<div>
<div className={this.props.className}>
<div className="label-wrapper">
{this.buildLabels()}
</div>
<div className="drum-wrapper">
{this.buildColumns()}
</div>
</div>
<div className="audio-wrapper">
{this.buildAudio()}
</div>
</div>
)
}
}
Here is "SixteenthNote.js" module
class SixteenthNote extends Component {
constructor(props) {
super(props);
this.buildColumn= this.buildColumn.bind(this);
this.buildDrumOptions = this.buildDrumOptions.bind(this);
this.updateActiveDrumsArray = this.updateActiveDrumsArray.bind(this);
this.state = {
activeDrums: []
}
}
buildDrumOptions() {
return this.props.drumOptions;
}
updateActiveDrumsArray(type) {
let array = this.state.activeDrums;
array.push(type);
this.setState({activeDrums: array});
}
buildColumn() {
const placeArray = this.buildDrumOptions().map((button, index) => {
return <Drum buttonClassName="drum__button" audioClassName="drum__audio" type={button.type} file={button.file} key={index} onClick={() => this.updateActiveDrumsArray(button.type)}/>
})
return placeArray;
}
render() {
return (
<div className={this.props.columnClassName}>
{this.buildColumn()}
</div>
)
}
}
Here is the "Drum.js" module
class Drum extends Component {
constructor(props) {
super(props);
this.clickFunction = this.clickFunction.bind(this);
this.state = {
clicked: false
}
}
drumHit(e) {
document.querySelector(`.audio[data-drum=${this.props.type}]`).play();
this.setState({clicked:true});
}
clickFunction(e) {
this.state.clicked === false ? this.drumHit(e) : this.setState({clicked:false})
}
render() {
const drumType = this.props.type;
const drumFile = this.props.file;
const buttonClasses = `${this.props.buttonClassName} drum-clicked--${this.state.clicked}`
return (
<div onClick={this.props.onClick}>
<button className={buttonClasses} data-type={drumType} onClick={this.clickFunction}></button>
</div>
)
}
}

You will need to contain the information about the activeDrums in your DrumMachine component.
That means:
In your DrumMachine component you create the state activeDrums like you have in your SixteenthNote.js. You will need to put your updateActiveDrumsArray function to your drumMachine component as well.
Then you pass this function to your SixteenthNote component like:
<SixteenthNote columnClassName="drum__column" key={index} drumOptions={this.state.drumOptions} onDrumsClick={this.updateActiveDrumsArray} />
After doing so, you can access that function via props. So, in your SixteenthNote component it should look like:
<Drum buttonClassName="drum__button" audioClassName="drum__audio" type={button.type} file={button.file} key={index} onClick={() => this.props.onDrumsClick(button.type)}/>
(Don't forget to get rid of the unneccessary code.)
With this, you have your activeDrums state in DrumMachine containing all the active drums. This state you can then send to your play component and do the play action there.

React doesn't render all components of array

I want to dynamically add Components, after clicking the "add" button.
For that, I created an array that consists of all the components, and add them on click.
My problem is, that it only renders one component, even though it consists of several ones.
My code looks like this:
class QuestionBlock extends React.Component {
constructor(props) {
super(props);
this.state = {answersArray: []};
}
addPossibleAnswer() {
this.state.answersArray.push(
<PossibleAnswers id={this.state.answersArray.length + 1}/>
)
this.forceUpdate();
}
componentWillMount() {
this.state.answersArray.push(
<PossibleAnswers id={this.state.answersArray.length + 1}/>
)
}
render() {
console.log(this.state.answersArray) // Grows after adding componenets, but they are not rendered.
return (
<div>
{this.state.answersArray}
<AddPossibleAnswer addPossibleAnswer={() => this.addPossibleAnswer()} />
</div>
);
}
}
If you see what I did wrong, I'd be really glad if you could help me out!

Instead of mutating state directly and adding JSX to it, you can instead keep raw data in your state and derive the JSX from that in the render method instead.
Example
class QuestionBlock extends React.Component {
state = { answers: 1 };
addPossibleAnswer = () => {
this.setState(({ answers }) => ({ answers: answers + 1 }));
};
render() {
return (
<div>
{Array.from({ length: this.state.answers }, (_, index) => (
<PossibleAnswers key={index} id={index} />
))}
<AddPossibleAnswer addPossibleAnswer={this.addPossibleAnswer} />
</div>
);
}
}

You don't interact with state like you do. Never mutate the state field. You need to use this.setState:
this.setState(prevState => ({answersArray: prevState.answersArray.concat([
<PossibleAnswers id={prevState.answersArray.length + 1}])}));
Having said that, it is also strange that you store components in state. Usually, you would store data and create the components based on the data in the render method.

You are directly pushing elements to the array without setState so the component won't re-render
Also avoid using tthis.forceUpdate() as much as you can in your application because this is not recommended much
You need to change your code like below. The recommended approach for dealing with arrays in react is using previous state and push to an array
addPossibleAnswer() {
this.setState(prevState => ({
answersArray: [...prevState.answersArray, <PossibleAnswers id={prevState.answersArray.length + 1}/>]
}));
}
componentWillMount() {
this.setState(prevState => ({
answersArray: [...prevState.answersArray, <PossibleAnswers id={prevState.answersArray.length + 1}/>]
}));
}
Also keep in mind that componentWillMount life cycle method is deprecated in react 16. So move the code to componentDidMount instead
Here is the corrected code
class QuestionBlock extends React.Component {
constructor(props) {
super(props);
this.state = {answersArray: []};
}
addPossibleAnswer() {
this.setState(prevState => ({
answersArray: [...prevState.answersArray, <PossibleAnswers id={prevState.answersArray.length + 1}/>]
}));
}
componentDidMount() {
this.setState(prevState => ({
answersArray: [...prevState.answersArray, <PossibleAnswers id={prevState.answersArray.length + 1}/>]
}));
}
render() {
const { answersArray } = this.state;
return (
<div>
{answersArray}
<AddPossibleAnswer addPossibleAnswer={() => this.addPossibleAnswer()} />
</div>
);
}
}

React mapped function running "setState" isn't updating component

I have an app component that takes one nested component. The nested component returns a number of buttons determined by one of its local state variable's lengths. Each button runs a programmatic this.setState() function to show a new set of data onClick. Here's the code described, and my question below:
class App extends React.Component {
render() {
return (
<div className='container'>
<Buttons />
</div>
)
}
}
class Buttons extends React.Component {
state = {
variableState,
count: 0,
chosen: 0,
}
upOne = x => {
this.setState(prevState => ({
count: prevState.count + 1,
chosen: x,
}))
console.log('running')
}
componentDidUpdate() {
console.log('componentupdated')
}
render() {
const {variableState, count, chosen} = this.state
const {upOne} = this
return (
<div>
{
variableState[count].answers.map((s, t) => <button onClick={() => upOne(t + 1)}>{s}</button>)
}
</div>
)
}
}
const variableState = [
{
answers: [
'one',
'two',
'three',
'four',
]
}
]
ReactDOM.render(<App />, document.getElementById('app'))
<div id="app"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
I want to update the <Buttons /> state by incrementing the count by one each time one of the buttons is clicked. This should run setState() which should update the component and run the componentDidUpdate() function. The problem is, the upOne() function runs, but it isn't updating the component and therefore not running the componentDidUpdate() function and I don't know why.
If I get rid of the Array.map() logic and make it a static function like this:
class Buttons extends React.Component {
state = {
variableState,
count: 0,
chosen: 0,
}
upOne = x => {
this.setState(prevState => ({
count: prevState.count + 1,
chosen: x,
}))
console.log('running')
}
componentDidUpdate() {
console.log('componentupdated')
}
render() {
const {variableState, count, chosen} = this.state
const {upOne} = this
return (
<button onClick={() => upOne(1)}>click</button>
)
}
}
It works as I expect it to.
Is this expected behavior or am I missing something?

variableState[count].answers...
Once counts becomes 1, variableState[1] is undefined and undefined.answers does not exists and you'll see an thrown error in your console.
I don't know if the variableStates value that you're showing in your code is the same as you're using on your end, but if you change it to variableState[0].answers..., it works.

How to remove an instance of a React component class instantiated by its parent's state?

(Pardon the verbose question. I'm brand new to React and ES6, and I'm probably overly-convoluting this.)
I am writing an app that contains a button component. This button calls a method onAddChild that creates another component of class ColorModule by adding a value to an array stored in the App's state.
In each newly created ColorModule, I want to include another button that will remove the module. Since this component is created by an array.map method, my thought is that if I can find the index of the array item that corresponds with the component and use that index in array.splice then perhaps that component will be removed (untested theory). That said, I'm not really sure how to find the index where I would use this in my onRemoveModule method.
Two part question: 1) How would I go about finding the index of the array item in my state, and 2) if I'm completely off base or there's a better way to do this altogether, what does that solution look like?
imports...
class App extends Component {
static propTypes = {
children: PropTypes.node,
};
constructor(props) {
super(props);
this.state = {
// Here's the array in question...
moduleList: [1],
};
this.onAddChild = this.onAddChild.bind(this);
this.onRemoveModule = this.onRemoveModule.bind(this);
this.className = bemClassName.bind(null, this.constructor.name);
}
onAddChild(module) {
const moduleList = this.state.moduleList;
this.setState({ moduleList: moduleList.concat(1) });
}
onRemoveModule( e ) {
e.preventDefault();
...¯\_(ツ)_/¯
}
render() {
const { className } = this;
return (
<div className={className('container')}>
<Header onAddChild={this.onAddChild} /> /* Add module button lives here */
<div className="cf">
{this.state.moduleList.map(
( delta, index ) => {
return (
<ColorModule
className="cf"
onRemove={this.onRemoveModule}
key={index}
moduleId={'colorModule' + index}
/>
); /* Remove module button would live in the module itself */
}
)}
</div>
</div>
);
}
}
export default App;

Well this part is pretty easy, all you need to do is pass the index as prop to the ColorModule component and when calling the onRemove method in it you could pass it back to the onRemoveModule. However react optimizes based on keys and its a really good idea to have a unique id given to each module instance.
class App extends Component {
static propTypes = {
children: PropTypes.node,
};
constructor(props) {
super(props);
this.state = {
// Here's the array in question...
moduleList: [1],
};
this.onAddChild = this.onAddChild.bind(this);
this.onRemoveModule = this.onRemoveModule.bind(this);
this.className = bemClassName.bind(null, this.constructor.name);
}
onAddChild(module) {
const moduleList = this.state.moduleList;
this.setState({ moduleList: moduleList.concat(uuid()) }); //uuid must return a unique id everytime to be used as component key
}
onRemoveModule( index ) {
// now with this index you can update the moduleList
}
render() {
const { className } = this;
return (
<div className="cf">
{this.state.moduleList.map(
( delta, index ) => {
return (
<ColorModule
className="cf"
index={index}
onRemove={this.onRemoveModule}
key={delta}
moduleId={'colorModule' + delta}
/>
);
}
)}
</div>
);
}
}
Now in ColorModule component
class ColorModule extends React.Component {
onRemoveClick=() => {
this.props.onRemove(this.props.index);
}
}
Check this answer for more details on how to pass data from Child component to Parent

I ended up solving this problem using some of the guidance here from #ShubhamKhatri (didn't know about unique ID generation!), but I took a slightly different approach and handled the solution using state manipulation in App without needing a new method in my ColorModule component. I also never knew about currying in ES6, so that discovery made passing in the index values needed to manipulate my state array possible
If I'm off-base here or being inefficient, I'm definitely still open to feedback on a better way!
class App extends Component {
constructor(props) {
super(props);
this.state = {
moduleList: [{ id: UniqId(), removeModule: false }],
};
this.onAddChild = this.onAddChild.bind(this);
this.className = bemClassName.bind(null, this.constructor.name);
}
onAddChild(module) {
const moduleList = this.state.moduleList;
this.setState({
moduleList: moduleList.concat({
id: UniqId(),
removeModule: false,
}),
});
}
onRemoveModule = ( i, arr ) => (e) => {
const moduleList = this.state.moduleList;
e.preventDefault();
moduleList[i].removeModule = true;
this.setState({ moduleList: moduleList });
}
render() {
const { className } = this;
return (
<div className={className('container')}>
<Header onAddChild={this.onAddChild} />
<div className="cf">
{this.state.moduleList.map(
( delta, index ) => {
if ( !this.state.moduleList[index].removeModule ) {
return (
<ColorModule
className="cf"
onRemove={this.onRemoveModule( index, this.state.moduleList )}
index={index}
key={delta.id}
moduleId={'colorModule' + delta}
/>
);
}
}
)}
</div>
</div>
);
}
}