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How to make reusable component in react-native and call them inside other component?

I have a modal component that I want to reuse in future component.
For this reason I want to have it in its own file.
I don't manage to call the component inside the other properly though.
Here is my last attempt of it.
The Modal component code:
export const FlyingDescription = (cityDescription) => {
const [modalVisible, setModalVisible] = useState(false);
return (
<View>
<Modal
animation="slide"
transparent={true}
visible={modalVisible}
onRequestClose={() => setModalVisible(!modalVisible)}
>
<View style={styleBoxParent}>
<View style={styleBoxChildren}>
<LinearGradient
style={styleLinearGradient}
colors={['#136a8a', '#267871']}
start={[0, 0.65]}
>
<Text style={styleText}>{cityDescription}</Text>
<Pressable
onPress={() => setModalVisible(!modalVisible)}
>
<Text style={styleText}>Close</Text>
</Pressable>
</LinearGradient>
</View>
</View>
</Modal>
</View>
);
};
The component where I want to call the Modal component:
import FlyingDescription from './FlyingDescription.js';
var utils = require('./utils');
export default class SearchScreen extends React.Component {
constructor(props) {
super(props);
this.navigation = props.navigation;
this.state = {
searchInput: '',
item : {},
renderSearch: false,
renderFlyingDescription: false,
};
this.errorMessage = 'Search for cities...';
}
resetState = () => {
this.setState({
item: {},
renderable: false,
}); }
setSearchInput = (value) => {
this.setState({
searchInput: value
});
}
searchCity = () => {
this.resetState();
utils.fetchWeather(this.state.searchInput).then(response => {
if (response.cod == 200) {
console.log(response);
this.setItemState(
{
name: response.name,
temp: Math.ceil(response.main.temp),
type: response.weather[0].main,
desc: 'Humidity: ' + response.main.humidity + '% - ' + response.weather[0].main
}
);
this.setRenderSearch();
}
});
}
setItemState = (newItem) => {
this.setState(
{
item: newItem,
}
);
}
setRenderSearch = () => {
this.setState(
{
renderSearch: true,
}
);
}
render = () => {
return(
<View style={utils.style.container}>
<StatusBar barStyle="light-content" />
<Text style={utils.style.titleContainer}>☀️ CityWeather</Text>
<View style={{alignItems: 'center', width:'90%'}}>
<Text>Search for a city</Text>
<TextInput
onChangeText={(value) => this.setSearchInput(value)}
value={this.searchInput}
style={{ width: '80%', padding: 15, margin: 5, backgroundColor: 'black', color: 'white' }}
/>
<TouchableHighlight
style={{backgroundColor: 'grey', padding: 20, borderRadius: 8}}
onPress={this.searchCity}
>
<Text style={{fontSize: 14, color:'white'}}>Search</Text>
</TouchableHighlight>
</View>
{ this.state.renderSearch ? (
<TouchableHighlight
underlayColor="white"
onPress={ () => this.setState({renderFlyingDescription: true})}
>
<LinearGradient
colors={['rgba(0,0,0,0.05)', 'rgba(0,0,0,0)']}
start={[0, 0.5]}
>
<View style={utils.style.row}>
<Text style={[utils.getTempRange(this.state.item.temp), utils.style.temp]}>
{utils.getEmoji(this.state.item.type)} {this.state.item.temp} °C
</Text>
<Text style={utils.style.cityName}>{this.state.item.name}</Text>
</View>
</LinearGradient>
</TouchableHighlight>
) : (
// WHERE I WANT TO RENDER MY MODAL COMPONENT
<View style={{flex: 1, justifyContent: 'center', alignItems: 'center', fontSize: 32}}>
<Text>{this.errorMessage}</Text>
</View>
)
}
{
renderFlyingDescription(this.state.renderFlyingDescription, this.state.item.desc)
}
</View>
);
}
}
export function renderFlyingDescription(isInterpretable, cityDescription) {
if(isInterpretable) {
return <FlyingDescription cityDescription={cityDescription} />
}
}

Navigation issue undefined is not an object (evaluating '_this2.props.navigation.navigate')

Hey guys I'm having an issue with navigation:
I select an item from the menuoption
I then call the 'testFunction'
Function will call an alert function so it is working
When I add the navigation part I get the error below:
undefined is not an object (evaluating '_this2.props.navigation.navigate')
Here is the import code:
import { NavigationScreenProp } from "react-navigation";
Here is where it is added to props:
interface NotificationDropdownProps {
navigation: NavigationScreenProp<any,any>
}
Here is where code is rendered:
class NotificationDropdown extends React.Component<Props, NotificationDropdownState> {
testFunction = () => {
this.props.navigation.navigate('Leagues')
};
<MenuOption
onSelect={() =>
{
if(notification.type == INotificationType.SYSTEM){
this.testFunction()
}
}
}
customStyles={{ optionWrapper: { padding: 0, margin: 0, zIndex: 100000000 } }}>
<View style={[styles.notificationContainer]} >
<View style={styles.iconArea}>
<View style={[styles.iconCircle]}>
<Icon name={this.getIconType(notification.type)}
color={this.notificationColor(notification.type)} size={26} />
</View>
</View>
<View style={styles.notificationData} >
<Text style={styles.notificationTxt}>{notification.text}</Text>
<Text style={styles.notificationDate}>{this.getDate(new Date(notification.dateCreated))}</Text>
</View>
</View>
</MenuOption>
Render:
render() {
return (
<Menu
renderer={Popover} rendererProps={{ placement: 'bottom', preferredPlacement: 'bottom' }}
opened={this.state.opened}
onBackdropPress={() => this.togglePopup()}
onClose={() => {
this.setState({ showEmpty: true });
// Store.dispatch(SetNotificationSeen());
}}
onOpen={() => {
Store.dispatch(SetNumberSeen(this.props.notifications.length));
}}
>
<MenuTrigger onPress={() => this.togglePopup()}>
<View style={{ padding: 10 }}>
<Icon name='ios-notifications-outline' color={'rgba(0,0,0,0.6)'} size={25} /></View>
</MenuTrigger>
<MenuOptions customStyles={{
optionsContainer: {
width: Dimensions.get('window').width * 0.75,
zIndex: 100000000,
elevation: 8,
borderRadius: 20
}
}}>
<View style={{ padding: 10 }}>
<Text style={{
fontSize: 20,
marginLeft: 10,
color: 'rgba(0,0,0,0.6)',
fontWeight: 'bold',
paddingBottom: 5
}}>Notifications</Text>
{this.props.notifications.length > 0 ? <FlatList
contentContainerStyle={{ borderRadius: 10 }}
// only allow 5 notifications
data={this.props.notifications.slice(0,5)}
renderItem={({ item }) => this.renderNotification(item)}
style={{ maxHeight: 200, zIndex: 5 }}
keyExtractor={this.keyExtractor}
/> : <Text style={styles.noNotifications}>No Notifications!</Text>}
</View>
</MenuOptions>
</Menu>
);
}
What am I missing? any help is welcome
Here is where the is called from the header.tsx
<View style={styles.icon}>
<NotificationDropdown />
{this.props.numberSeen < this.props.notificationCount ? <Badge value={this.props.notificationCount - this.props.numberSeen > 99 ? '99+' : this.props.notificationCount - this.props.numberSeen}
status="error" containerStyle={styles.badge} /> : null}
</View>

Ok so it seems that NavigationDropDown doesn't have the navigation props.
What you need is to pass the navigation props explicitly as it is not a screen component.
in the headercomponent.tsx
<View style={styles.icon}>
<NotificationDropdown navigation={this.props.navigation} />
{this.props.numberSeen < this.props.notificationCount ? <Badge value={this.props.notificationCount - this.props.numberSeen > 99 ? '99+' : this.props.notificationCount - this.props.numberSeen}
status="error" containerStyle={styles.badge} /> : null}
</View>
I assume that you have the navigation props in the headercomponent.tsx

how do i get and show the total sum objects that arrive from my JSON in a footer at the bottom of the screen?

At my example, the function “getData” loading my data, but after the loading, I try to print and show the total sum of the objects that came from JSON in a footer at the bottom of the screen.
and I don't really know how to do it.
I don't understand how to solve this issue coz I have tried many ways.
This is my example:
export default class MainScreen extends Component {
constructor(props) {
super(props);
this.state = { data: [] };
}
getData = () => {
this.setState({ isLoading: true })
axios.get("https://rallycoding.herokuapp.com/api/music_albums")
.then(res => {
this.setState({
isLoading: false,
data: res.data
});
console.log(res.data);
});
}
componentDidMount() {
this.props.navigation.setParams({getData: this.getData}); //Here I set the function to parameter
this.getData()
}
renderItem(item) {
const { title, artist} = item.item;
return (
<TouchableOpacity
onPress={() => this.props.navigation.navigate("Settings")}
>
<Card
containerStyle={{
borderColor: "black",
padding: 20,
height: 100,
backgroundColor: "#e6e6ff",
borderBottomEndRadius: 10,
borderTopRightRadius: 10,
borderBottomStartRadius: 10,
}}
>
<View
style={{
paddingVertical: 15,
paddingHorizontal: 10,
flexDirection: "row",
justifyContent: "space-between",
alignItems: "center"
}}
>
<Icon name="chevron-right" size={30} color={"grey"} justifyContent={"space-between"} />
<Text style={styles.name}>
{title+ " " + artist}
</Text>
{/* <Text style={styles.vertical} numberOfLines={2}></Text> */}
</View>
</Card>
</TouchableOpacity>
);
}
render() {
if (this.state.isLoading) {
return (
<View style={{ flex: 1, paddingTop: 230 }}>
<Text
style={{ alignSelf: "center", fontWeight: "bold", fontSize: 20 }}
>
loading data...
</Text>
<ActivityIndicator size={'large'} color={'#08cbfc'} />
</View>
);
}
return (
<View style={styles.container}>
<FlatList
data={this.state.data}
renderItem={this.renderItem.bind(this)}
keyExtractor={item => item.id}
/>
</View>
);
}
}
/////////////////////////////////////////////////////////
MainScreen.navigationOptions = navData => {
return {
headerTitle: 'melon',
headerRight: (
<HeaderButtons HeaderButtonComponent={HeaderButton}>
<Item
title=**"sync button"**
iconName={Platform.OS === "android" ? "md-sync" : "ios-sync"}
onPress={() => {
navData.navigation.navigate("getData");
}}
/>
</HeaderButtons>
)
};
};

If type of data is array you can get total number of elements by this.state.data.length
If type of data is object you can get total number of elements by Object.keys(data).length

React Native Picker Placeholder

I have a custom iOS Picker Modal component and I want to add placeholder on it, is there anyway to do that? And my pickers are generated by map function, here is my picker code
class PickerWrapper extends React.Component {
constructor(props) {
super(props);
this.state = {
type_absen: '',
modal: false
}
}
render() {
let picker;
let iosPickerModal = (
<Modal isVisible={this.state.modal} hideModalContentWhileAnimating={true} backdropColor={color.white} backdropOpacity={0.9} animationIn="zoomInDown" animationOut="zoomOutUp" animationInTiming={200} animationOutTiming={200} onBackButtonPress={() => this.setState({ modal: false })} onBackdropPress={() => this.setState({ modal: false })} >
<View style={{ backgroundColor: color.white, width: 0.9 * windowWidth(), height: 0.3 * windowHeight(), justifyContent: 'center' }}>
<Picker
selectedValue={this.state.type_absen}
onValueChange={(itemValue, itemIndex) => {
this.setState({ type_absen: itemValue });
this.setState({ modal: false });
setTimeout(() => this.props.onSelect(itemValue), 1200);
}}
>
{this.props.items.map((item, key) => <Picker.Item label={item.description} value={item.id} key={item.id} />)}
</Picker>
</View>
</Modal>);
if (Platform.OS === 'ios') {
var idx = this.props.items.findIndex(item => item.id === this.state.type_absen);
return (
<View style={this.props.style}>
{iosPickerModal}
<TouchableOpacity onPress={() => this.setState({ modal: true })}>
<View style={{ flexDirection: 'row', height: this.props.height ? this.props.height : normalize(40), width: this.props.width ? this.props.width : 0.68 * windowWidth(), borderWidth: 1, borderColor: color.blue, alignItems: 'center', borderRadius: 5 }}>
<Text style={{ fontSize: fontSize.regular, marginRight: 30 }}> {idx !== -1 ? this.props.items[idx].description : this.state.type_absen}</Text>
<IconWrapper name='md-arrow-dropdown' type='ionicon' color={color.light_grey} size={20} onPress={() => this.setState({ modal: true })} style={{ position: 'absolute', right: 10 }} />
</View>
</TouchableOpacity>
</View >);
}
}

unshift defualt value and label in the items array then check it in onValueChange
iosPickerModal = () => {
let makeitems = this.props.items;
// unshift defualt value and label
makeitems.unshift({
label: 'Please select an option...',
value: '-1',
});
return (
<Modal isVisible={this.state.modal} hideModalContentWhileAnimating={true} backdropColor={color.white} backdropOpacity={0.9} animationIn="zoomInDown" animationOut="zoomOutUp" animationInTiming={200} animationOutTiming={200} onBackButtonPress={() => this.setState({ modal: false })} onBackdropPress={() => this.setState({ modal: false })} >
<View style={{ backgroundColor: color.white, width: 0.9 * windowWidth(), height: 0.3 * windowHeight(), justifyContent: 'center' }}>
<Picker
selectedValue={this.state.type_absen}
onValueChange={(itemValue, itemIndex) => {
if (itemValue === '-1') return null;
this.setState({ type_absen: itemValue });
this.setState({ modal: false });
setTimeout(() => this.props.onSelect(itemValue), 1200);
}}
>
{makeitems.map((item, key) => <Picker.Item label={item.description} value={item.id} key={item.id} />)}
</Picker>
</View>
</Modal>)
};
render(){
if (Platform.OS === 'ios') {
var idx = this.props.items.findIndex(item => item.id === this.state.type_absen);
return (
<View style={this.props.style}>
{this.iosPickerModal}
<TouchableOpacity onPress={() => this.setState({ modal: true })}>
<View style={{ flexDirection: 'row', height: this.props.height ? this.props.height : normalize(40), width: this.props.width ? this.props.width : 0.68 * windowWidth(), borderWidth: 1, borderColor: color.blue, alignItems: 'center', borderRadius: 5 }}>
<Text style={{ fontSize: fontSize.regular, marginRight: 30 }}> {idx !== -1 ? this.props.items[idx].description : this.state.type_absen}</Text>
<IconWrapper name='md-arrow-dropdown' type='ionicon' color={color.light_grey} size={20} onPress={() => this.setState({ modal: true })} style={{ position: 'absolute', right: 10 }} />
</View>
</TouchableOpacity>
</View >);
}
}

Child component inside modal unexpectedly resets to default state, React Native

I have a parent component--LeagueSelect--and a child component TeamSelect.
LeagueSelect is a React Native modal.
When I open LeagueSelect, make adjustments in the LeagueSelect modal, collapse the modal, and open it again, the state changes are preserved.
If I open LeagueSelect, make adjustments to TeamSelect in the LeagueSelect modal, collapse the modal, and open it again, the state changes are not preserved.
To provide context, when the modal (LeagueSelect) is open, this is what it looks like; the first red box is part of LeagueSelect, and the second red box is part of TeamSelect:
This is my LeagueSelect component; I think the issue is happening in setModalVisible, because the console logs read the correct state when I console.log the state on componentWillUnmount:
class LeagueSelect extends Component {
constructor(props) {
super(props)
this.state = {
modalVisible: false,
checked: [],
checkedLeagues: [],
uncheckedLeagues: [],
checkMessage: '',
firstString: []
}
}
setModalVisible(visible) {
this.setState({modalVisible: visible})
if(this.state.checked.length === 0) {
this.props.league.map(
(v, i) => {
this.state.checked.push(true)
this.state.checkedLeagues.push(v.acronym)
}
)
}
this.setState({ checkMessage: '' })
matchedTeams = []
if(undefined !== this.props.teamObject) {
this.props.teamObject.map(
(v, i) => {
if(this.state.checkedLeagues.includes(v.league.acronym)){
matchedTeams.push(v.team_name)
}
}
)
}
queryString = []
//encodes the teams that have their leagues selected
matchedTeams.map(
(v, i) => {
if (queryString.length < 1) {
queryString.push(`?team=${v}`)
} else if (queryString.length >= 1 ) {
queryString.push(`&team=${v}`)
}
}
)
queryString = queryString !== undefined ? queryString.join('') : ''
axios.get(`http://localhost:4000/reports${queryString}`)
.then(response => {
this.props.loadCards(response.data)
})
}
componentDidMount() {
this.props.loadLeagues()
this.props.loadTeams()
}
componentDidUpdate(){
console.log(this.props.checkedLeagues)
console.log('in league - in update - checked Teams', this.props.checkedTeams)
this.props.changeLeagues(this.props.league, this.state.checkedLeagues, this.props.checkedTeams, this.props.queryTeams, this.props.teamObject)
}
render(){
return (
<View style={{ position: 'relative'}}>
<Modal
animationType="slide"
transparent={false}
visible={this.state.modalVisible}
onRequestClose={() => {
Alert.alert('Modal has been closed.');
}}
>
<View
style={{
marginTop: 100
}}
>
<TouchableHighlight
onPress={() => {
this.setModalVisible(!this.state.modalVisible);
}}
>
<Image
source={require('../assets/exit.png')}
style={{
height: 20,
width: 20,
left: 320,
resizeMode: 'contain'
}}
/>
</TouchableHighlight>
<Text
style={{
paddingTop: 8,
paddingLeft: 5,
fontSize: 15,
fontFamily: 'Helvetica',
fontSize: 13
}}
>LEAGUE SELECT</Text>
<View
style={{
flexDirection:"row",
paddingLeft: 10
}}
>
{this.props.league === null ?'' : this.props.league.map(
(v, i) => {
return(
<View
key={i}
style={{
alignSelf: 'flex-end',
flexDirection:"row",
top: 4,
paddingRight: 10
}}
>
<Check
checked={this.state.checked[i]}
index={i}
value={v.acronym}
changeCheck={this.changeCheck}
style={{
paddingRight: 10
}}
/>
</View>
)
}
)}
</View>
<Text
style={{
paddingLeft: 10,
paddingTop: 12,
fontStyle: 'italic',
color: '#F4AF0D'
}}
>{this.state.checkMessage}</Text>
<TeamSelect />
</View>
</Modal>
<TouchableHighlight
onPress={() => {
this.setModalVisible(true);
}}>
<Icon
style={{
position: 'absolute',
top: -34,
right: 10,
fontSize: 25,
color: 'grey'
}}
name='settings'
/>
</TouchableHighlight>
</View>
);
}
}
function mapStateToProps(state) {
return {
league: state.league.league,
team: state.team.team,
checkedLeagues: state.league.checkedLeagues,
checkedTeams: state.league.checkedTeams,
queryTeams: state.league.queryTeams,
teamObject: state.league.teamObject
}
}
export default connect(mapStateToProps, { loadCards, loadLeagues, loadTeams, changeLeagues })(LeagueSelect)
This is the TeamSelect component where the second red box's selections are made:
class TeamSelect extends Component {
constructor(props) {
super(props)
this.state = {
checked: [],
checkedTeams: [],
teamObject: [],
queryString: [],
accordionStatus: [true, true, true]
}
}
componentDidMount(){
console.log('did mount - checked Teams State', this.state.checkedTeams)
//updates checked teams on load
if(this.state.count === false && this.state.checkedTeams.length === 0 && this.state.checked.length === 0){
this.setState({ count: true})
this.props.team.map(
(v, i) => {
if(this.props.checkedLeagues.includes(v.league.acronym)) {
this.state.checked.push(true)
this.state.checkedTeams.push(v.team_name)
this.state.teamObject.push(v)
} else if (this.state.checkedTeams !== undefined) {
this.state.checked.push(false)
}
}
)
this.forceUpdate()
}
}
componentWillUnmount(){console.log("unmount - count", this.state.count)
console.log('will unmount - checked Teams State', this.state.checkedTeams)
}
componentDidUpdate(){
this.props.changeLeagues(this.props.league, this.props.checkedLeagues, this.state.checkedTeams, this.state.queryString, this.state.teamObject)
}
changeCheck = (index, name, teamObject) => {
//updates checked team state
//prevents all teams being unselected
if(name === this.state.checkedTeams[0]) {
this.setState({ checkMessage: `Don't you want something to look at?` })
} else {
if(!this.state.checkedTeams.includes(name)){
this.state.checkedTeams[this.state.checkedTeams.length] = name
this.setState({ checkedTeams: [...this.state.checkedTeams] })
//sets team object with new team object
this.state.teamObject[this.state.teamObject.length] = teamObject
this.setState({ teamObject: this.state.teamObject })
} else {
newChecked = this.state.checkedTeams.filter(v => { return v !== name})
this.setState({ checkedTeams: newChecked })
//removes team object and sets new state
newObjectChecked = this.state.teamObject.filter(v => { return v.team_name !== teamObject.team_name})
this.setState({ teamObject: newObjectChecked })
}
//updates checkbox for specific space
this.state.checked[index] = !this.state.checked[index]
this.setState({ checked: this.state.checked })
}
}
changeTeamSelect = (index) => {
this.state.accordionStatus[index] = !this.state.accordionStatus[index]
this.setState({ accordionStatus: this.state.accordionStatus})
}
render(){
return(
<View>
<View>
<Text
style={{
fontFamily: 'Helvetica',
fontSize: 13,
paddingLeft: 5,
paddingBottom: 5
}}
onPress={()=> this.changeTeamSelect(0)}
>
NFL TEAM SELECT
</Text>
</View>
{
this.state.accordionStatus[0] === false ? null :
<View
style={{
flexDirection: 'row',
paddingLeft: 10,
flexWrap: 'wrap'
}}
>
{
this.props.team.map(
(v, i) => {
if(v.league.acronym === 'NFL'){
return(
<Check
key={i}
checked={ /*this.props.checkedLeagues.includes(v.league.acronym) ?*/ this.state.checked[i] /*: false*/ }
index={i}
teamObject={v}
value={v.team_name}
changeCheck={this.changeCheck}
/>
)
}
}
)
}
</View>
}
<View>
<Text
style={{
fontFamily: 'Helvetica',
fontSize: 13,
paddingLeft: 5,
paddingBottom: 5
}}
onPress={()=> this.changeTeamSelect(1)}
>
NBA TEAM SELECT
</Text>
</View>
{
this.state.accordionStatus[1] === false ? null :
<View
style={{
flexDirection: 'row',
paddingLeft: 10,
flexWrap: 'wrap'
}}
>
{
this.props.team.map(
(v, i) => {
if(v.league.acronym === 'NBA'){
return(
<Check
key={i}
checked={ /*this.props.checkedLeagues.includes(v.league.acronym) ?*/ this.state.checked[i] /*: false*/ }
index={i}
teamObject={v}
value={v.team_name}
changeCheck={this.changeCheck}
/>
)
}
}
)
}
</View>
}
<View>
<Text
style={{
fontFamily: 'Helvetica',
fontSize: 13,
paddingLeft: 5,
paddingBottom: 5
}}
onPress={()=> this.changeTeamSelect(2)}
>
MLB TEAM SELECT
</Text>
</View>
{
this.state.accordionStatus[2] === false ? null :
<View
style={{
flexDirection: 'row',
paddingLeft: 10,
flexWrap: 'wrap'
}}
>
{
this.props.team.map(
(v, i) => {
if(v.league.acronym === 'MLB'){
return(
<Check
key={i}
checked={ /*this.props.checkedLeagues.includes(v.league.acronym) ?*/ this.state.checked[i] /*: false */}
index={i}
teamObject={v}
value={v.team_name}
changeCheck={this.changeCheck}
/>
)
}
}
)
}
</View>
}
</View>
)
}
}
function mapStateToProps(state) {
return {
league: state.league.league,
team: state.team.team,
checkedLeagues: state.league.checkedLeagues,
checkedTeams: state.league.checkedTeams,
queryTeams: state.league.queryTeams
}
}
export default connect(mapStateToProps, { loadCards, changeLeagues })(TeamSelect)
Something to note, I use redux to update the state, place it into a store, and then use it when the component is mounts again. What is interesting is that this.state.checkedLeagues preserves state as it should in the first component, however, this.state.checkedTeams does not preserve it's state in the second component. Any ideas why?
EDIT:
This is my LeagueReducer:
let defaultState = {
league: null,
checkedLeagues: null,
checkedTeams: null,
queryTeams: null,
teamObject: null
}
export function LeagueReducer(state = defaultState, action){
if(action.type === "CHANGE_LEAGUES") {
return {
...state,
league: action.league,
checkedLeagues: action.checkedLeagues,
checkedTeams: action.checkedTeams,
queryTeams: action.queryTeams,
teamObject: action.teamObject
}
} else {
return state
}
}

Looks like it's possible you're not updating the redux store correctly. Remember do not use array functions that mutate the array like push. You need to use functions like concat that return a new array.