I am trying to add an array of to my state of beer. What I am looking to accomplish is based on the users choice of favorite beers it adds those specific values on to the state.
the error I am receiving is that 'undefined is not a function' that points to my function to add the state.
import React, { Component } from 'react';
import { View, Text, Picker, StyleSheet } from 'react-native'
class BeerPicker extends Component {
constructor(props){
super(props);
this.state = {
beer: []
};
}
addBeer(newbeer){ <== function throws error
this.setState((state) => {
beer: state.addBeer.push(newbeer)
});
}
render() {
return (
<View>
<Picker selectedValue = {this.state.beer} onValueChange = {this.addBeer}>
<Picker.Item label = "IPA" value = "ipa" />
<Picker.Item label = "Pilsner" value = "pilsner" />
<Picker.Item label = "Stout" value = "stout" />
</Picker>
<Text style = {styles.text}>{this.state.beer}</Text>
</View>
)
}
}
export default BeerPicker;
const styles = StyleSheet.create({
text: {
fontSize: 30,
alignSelf: 'center',
color: 'red'
}
})
Fairly new to React Native so any input would be much accomplished!
The callback to Picker gives you itemValue and itemIndex, you'll have to push this in your beer array and do a bind in constructor
constructor(props){
super(props);
this.state = {
beer: []
};
this.addBeer = this.addBeer.bind(this);
}
addBeer(itemValue, itemIndex){
this.setState((state) => {
beer: [...state.beer, itemValue]
});
}
his problem seems to be context.
try using bind inside your constructor.
this.addBeer = this.addBeer.bind(this);
constructor(props){
super(props);
this.state = {
beer: []
};
this.addBeer = this.addBeer.bind(this);
}
You need to bind addBeer inside your constructor and additionally change your addBeer function to this:
addBeer(newbeer) {
this.setState({
beer: [...this.state.addBeer, newbeer]
});
}
Along with adding this.addBeer = this.addBeer.bind(this) to your constructor...you should also not make it a habit to use a mutator such as .push() in set state.
Try replacing addBeer() with:
addBeer(newbeer){
this.setState({
beer: [...this.state.beer, newbeer]
});
}
Related
I am trying to update the state in a method start() and then passing the state's value to MyComponent.
My component works ok, and the state updates ok when I'm setting it within the class, but when I'm trying to pass it from start method - it doesn't work. getting "TypeError: this.setState is not a function"
Edited - fixed binding but something still doesn't work.
What can be the problem?
export default class App extends Component{
constructor (props){
super(props);
this.state = {
val: false
}
this.start= this.start.bind(this)
}
start() {
this.setState({ val: true })
}
render(){
return (
<View>
<Button
title='start'
onPress={this.start}>
</Button>
<MyComponent value={this.state.val}> </MyComponent>
</View>
);
}
}
this is MyComponent:
class MyComponent extends Component {
constructor(props){
super(props)
this.state={}
this.state.custum={
backgroundColor: 'red'
}
let intervalid;
if (this.props.value){
setTimeout(() => {
this.setState( {
custum:{
backgroundColor: 'green'
}
})
}, 1000);
setTimeout(() => {
this.setState( {
custum:{
backgroundColor: 'red'
}
})
}, 2000);
}
}
render() {
return (
<View style={[styles.old, this.state.custum]}>
</View>
);
}
}
var styles = StyleSheet.create({
old:{
padding: 5,
height: 80,
width: 80,
borderRadius:160,
},
})
export default MyComponent;
You have to bind the context to your function.
constructor (props){
super(props);
this.state = {
val: false
}
this.start = this.start.bind(this)
}
or just you can an arrow function, without binding
start = () => {
this.setState({ val: true })
}
bind start method to the component other 'this' will be undefined for the start function
export default class App extends Component{
constructor (props){
super(props);
this.state = {
val: false
}
this.start = this.start.bind(this)
}
start() {
this.setState({ val: true })
}
render(){
return (
<View>
<Button
title='start'
onPress={this.start}>
</Button>
<MyComponent value={this.state.val}> </MyComponent>
</View>
);
}
}
You need to make start function to be binded through constructor or ES6 arrow function.
export default class App extends Component{
constructor (props){
super(props);
this.state = {
val: false
}
}
start = () => {
this.setState({ val: true })
}
render(){
return (
<View>
<Button
title='start'
onPress={this.start}>
</Button>
<MyComponent value={this.state.val}> </MyComponent>
</View>
);
}
}
You have to bind the method with this. Just add
this.start = this.start.bind(this)
after this.state in the constructor.
EDIT
And also try to move custom inside state in MyComponent like this:
this.state={
custum: {
backgroundColor: 'red'
}
}
and remove
this.state.custum={
backgroundColor: 'red'
}
As you can't just set state like this.
I have a component where when I click on an icon, I execute a function that modify a state and then i can check the state and modify the icon. In that comonent, I am mapping datas and it renders several items.
But when I click on one icon all the icons of the components change too.
Here is the code for the component
export default class DiscoveryComponent extends Component {
constructor(props) {
super(props)
this.state = {
starSelected: false
};
}
static propTypes = {
discoveries: PropTypes.array.isRequired
};
onPressStar() {
this.setState({ starSelected: !this.state.starSelected })
}
render() {
return (
this.props.discoveries.map((discovery, index) => {
return (
<Card key={index} style={{flex: 0}}>
<CardItem>
<TouchableOpacity style={[styles.star]}>
<Icon style={[styles.iconStar]} name={(this.state.starSelected == true)?'star':'star-outline'} onPress={this.onPressStar.bind(this)}/>
</TouchableOpacity>
</CardItem>
</Card>
)
})
);
}
}
And here is the code for my screen that uses the component
export default class DiscoveryItem extends Component {
constructor(props) {
super(props);
this.state = {
discoveries: [],
loading: true
};
}
componentDidMount() {
firebase.database().ref("discoveries/").on('value', (snapshot) => {
let data = snapshot.val();
let discoveries = Object.values(data);
this.setState({discoveries: discoveries, loading: false});
});
}
render() {
return (
<Container>
<Content>
<DiscoveryComponent discoveries={this.state.discoveries} />
</Content>
</Container>
)
}
}
Your initiation is correct but you are missing INDEX of each item. Inside this.onPressStar() method check if item's index = currentItem. Also don't forget to set item id = index onpress.
I hope this has given you idea how to handle it.
You have to turn your stars into an Array and index them:
change your constructor:
constructor(props) {
super(props)
this.state = {
starSelected: []
};
}
change your onPressStar function to :
onPressStar(index) {
this.setState({ starSelected[index]: !this.state.starSelected })
}
and your icon to
<Icon style={[styles.iconStar]} name={(this.state.starSelected[index] == true)?'star':'star-outline'} onPress={()=>this.onPressStar(index)}/>
Well, the problem is that you have a single 'starSelected' value that all of your rendered items in your map function are listening to. So when it becomes true for one, it becomes true for all.
You should probably maintain selected state in the top level component, and pass down the discovery, whether its selected, and how to toggle being selected as props to a render function for each discovery.
export default class DiscoveryItem extends Component {
constructor(props) {
super(props);
this.state = {
discoveries: [],
selectedDiscoveries: [] // NEW
loading: true
};
}
toggleDiscovery = (discoveryId) => {
this.setState(prevState => {
const {selectedDiscoveries} = prevstate
const discoveryIndex = selectedDiscoveries.findIndex(id => id === discoveryId)
if (discoveryIndex === -1) { //not found
selectedDiscoveries.push(discoveryId) // add id to selected list
} else {
selectedDiscoveries.splice(discoveryIndex, 1) // remove from selected list
}
return {selectedDiscoveries}
}
}
componentDidMount() {
firebase.database().ref("discoveries/").on('value', (snapshot) => {
let data = snapshot.val();
let discoveries = Object.values(data);
this.setState({discoveries: discoveries, loading: false});
});
}
render() {
return (
<Container>
<Content>
{
this.state.discoveries.map(d => {
return <DiscoveryComponent key={d.id} discovery={d} selected={selectedDiscoveries.includes(d.id)} toggleSelected={this.toggleDiscovery} />
//<DiscoveryComponent discoveries={this.state.discoveries} />
</Content>
</Container>
)
}
}
You can then use your DiscoveryComponent to render for each one, and you're now maintaining state at the top level, and passing down the discovery, if it is selected, and the toggle function as props.
Also, I think you may be able to get snapshot.docs() from firebase (I'm not sure as I use firestore) which then makes sure that the document Id is included in the value. If snapshot.val() doesn't include the id, then you should figure out how to include that to make sure that you use the id as both key in the map function as well as for the selectedDiscoveries array.
Hope that helps
It works now, thanks.
I've made a mix between Malik and Rodrigo's answer.
Here is the code of my component now
export default class DiscoveryComponent extends Component {
constructor(props) {
super(props)
this.state = {
tabStarSelected: []
};
}
static propTypes = {
discoveries: PropTypes.array.isRequired
};
onPressStar(index) {
let tab = this.state.tabStarSelected;
if (tabStar.includes(index)) {
tabStar.splice( tabStar.indexOf(index), 1 );
}
else {
tabStar.push(index);
}
this.setState({ tabStarSelected: tab })
}
render() {
return (
this.props.discoveries.map((discovery, index) => {
return (
<Card key={index} style={{flex: 0}}>
<CardItem>
<Left>
<Body>
<Text note>{discovery.category}</Text>
<Text style={[styles.title]}>{discovery.title}</Text>
</Body>
</Left>
<TouchableOpacity style={[styles.star]}>
<Icon style={[styles.iconStar]} name={(this.state.tabStarSelected[index] == index)?'star':'star-outline'} onPress={()=>this.onPressStar(index)}/>
</TouchableOpacity>
</CardItem>
</Card>
)
})
);
}
}
I've been using React native for a month now but it's my first time to use a CheckBox in my application. So, lately I've been struggling to check a specific checkbox inside a Flatlist but now I can.
But upon testing my checkboxs I did notice that once I check a specific a CheckBox(or more than 1 checkbox) it doesn't UNCHECK.
So, my goal is to make a CheckBox that can check(ofcourse) and also uncheck, if ever a user mischeck or mistap a CheckBox.
Here's my code
export default class tables extends Component {
constructor(props){
super(props)
this.state = {
...
check: false
}
}
checkBox_Test = (item, index) => {
let { check } = this.state;
check[index] = !check[index];
this.setState({ check: check })
alert("now the value is " + !this.state.check);
alert("now the value is " + item.tbl_id);
console.log(item.tbl_id)
}
render() {
return(
<View>
....
<Flatlist
....
<CheckBox
value = { this.state.check }
onChange = {() => this.checkBox_Test(item) }
/>
....
/>
<View/>
)
}
}
Method 1: Make check an object
export default class tables extends Component {
constructor(props){
super(props)
this.state = {
...
check: {}
}
}
checkBox_Test = (id) => {
const checkCopy = {...this.state.check}
if (checkCopy[id]) checkCopy[id] = false;
else checkCopy[id] = true;
this.setState({ check: checkCopy });
}
render() {
return(
<View>
....
<Flatlist
....
<CheckBox
value = { this.state.check[item.tbl_id] }
onChange = {() => this.checkBox_Test(item.tbl_id) }
/>
....
/>
<View/>
)
}
}
Method 2: Make a separate item for each FlatList item
class ListItem extends Component {
constructor(props){
super(props)
this.state = {
...
check: false
}
}
checkBox_Test = (id) => {
this.setState((prevState) => ({ check: !prevState.check }));
}
render() {
return(
<View>
<CheckBox
value = { this.state.check }
onChange = { this.checkBox_Test }
/>
</View>
)
}
}
Let me know if it works for you
I'm new to react native. I am trying to get 'Key' without using the onpress in button.
I just want to get a 'key', when i could open component. How it could be possible?
import React, { Component } from 'react';
import {
AppRegistry,
StyleSheet,
Text,
TextInput,
Button,
View,
AsyncStorage
} from 'react-native';
export default class History extends Component {
constructor(props) {
super(props);
this.state = {
myKey: null
}
}
async getKey() {
try {
const value = await AsyncStorage.getItem('#MySuperStore:key');
this.setState({ myKey: value });
} catch (error) {
console.log("Error retrieving data" + error);
}
}
render() {
return (
<View style={styles.container}>
<Button
style={styles.formButton}
onPress={this.getKey.bind(this)}
title="Get Key"
color="#2196f3"
accessibilityLabel="Get Key"
/>
<Text >
Stored key is = {this.state.myKey}
</Text>
</View>
)
}
}
const styles = StyleSheet.create({
container: {
padding: 30,
flex: 1,
backgroundColor: '#F5FCFF',
},
});
I am able to get a key with onpress but i want without onpress. Please suggest.
You can simply get your key value with componentDidMount. As you should know, when the App runs and comes to the current screen, there is a flow of methods will be called before and after rendering the render function. So ComponentDidMount comes after render function is called. So since you need to only display the key value, just follow below code.
constructor(props) {
super(props);
this.state = {
myKey:''
}
}
getKey = async() => {
try {
const value = await AsyncStorage.getItem('#MySuperStore:key');
this.setState({ myKey: value });
} catch (error) {
console.log("Error retrieving data" + error);
}
}
componentDidMount(){
this.getKey();
}
render() {
return (
<View style={styles.container}>
<Button
style={styles.formButton}
onPress={this.getKey.bind(this)}
title="Get Key"
color="#2196f3"
accessibilityLabel="Get Key"
/>
<Text >
Stored key is {this.state.myKey}
</Text>
</View>
)
}
Whenever render function being called, in that time, still key value is not set. So, this.state.myKey would be just Stored key is. But after that, once the componentDidMount called, it sets the myKey value and change states. Which will trig render function to render everything again. That would show your key value within the text component eventually without touching any button.
I am trying to make a simple clock that starts and stops on the press of a button. Here I have set a variable equal to a setInterval so that I can clear it later on. But for some reason, it is being called without the button being pressed.
Here the autoInc should have been called ideally when I pressed the "Start" button but it gets called anyway.
import React, { Component } from "react";
import { Text, View, Button } from "react-native";
export default class Counter extends Component {
increaser = () => {
this.setState(prePre => {
return { counter: prePre.counter + 1 };
});
};
constructor(props) {
super(props);
this.state = {
counter: 0,
wantToShow: true
};
autoInc = setInterval(this.increaser, 1000);
}
render() {
if (this.state.wantToShow)
return (
<View>
<Text style={{ color: "red", fontSize: 50, textAlign: "center" }}>
{this.state.counter}
</Text>
<Button title="Start" onPress={this.autoInc} />
</View>
);
}
}
A full react example here, you just have to translate functions in react native.
Create a variable this.interval=null in your constructor, assign to this the interval in the startFn , then just remove it with window.clearInterval(this.interval);
export default class App extends Component {
constructor(props) {
super(props);
this.interval = null;
}
componentDidMount() {}
startFn = () => {
console.log("assign and start the interval");
this.interval = setInterval(this.callbackFn, 1000);
};
stopFn = () => {
console.log("clear interval");
window.clearInterval(this.interval);
};
callbackFn = () => {
console.log("interval callback function");
};
render(props, { results = [] }) {
return (
<div>
<h1>Example</h1>
<button onClick={this.startFn}>start Interval</button>
<button onClick={this.stopFn}>stop Interval</button>
</div>
);
}
}
Codesandbox example here: https://codesandbox.io/s/j737qj23r5
In your constructor, you call setInterval(this.increaser,1000) and then assign its return value to the global property autoInc.
this.autoInc is undefined in your render function.
It looks like
autoInc = setInterval(this.increaser,1000)
is simply incorrectly written and what you want instead is:
this.autoInc = () => setInterval(this.increaser,1000)