I managed to get data from a my json.server into the desired component using the React-Redux methods, useSelector and useDispatch along with React's useEffect method.
What's confusing me is that even though the content of the array is there, the key for it is showing as undefined.
The console output:
Screenshot of console log
The component:
import React, { useEffect } from 'react';
import SetlistItem from './SetlistItem';
import { fetchSongs } from '../../actions/index'
import { useSelector, useDispatch } from 'react-redux';
const SetlistContainer = () => {
const songs = useSelector(state => state);
const dispatch = useDispatch();
useEffect(() => {
dispatch(fetchSongs())
}, [dispatch])
console.log(songs)
return <div><SetlistItem /></div>
}
export default SetlistContainer;
The action:
export const fetchSongs = () => async dispatch => {
const response = await songEntries.get("/songEntries");
dispatch({ type: FETCH_SONGS, payload: response.data });
}
The reducer:
export default (state = {}, action) => {
switch (action.type) {
case FETCH_SONGS:
return { ...state, [action.payload.id]: action.payload };
case CREATE_SONG:
return { ...state, [action.payload.id]: action.payload };
default:
return state;
}
}
The db.json:
{
"songEntries": [
{
"id": 1,
"songTitle": "This is a song title",
"notes": "These are some notes"
}
]
}
I found the problem.
I needed to use the mapKeys method from the lodash library.
I should have made it clearer in the op that I'm trying to fetch an array of records, even though rather unhelpfully, I've only placed one element in the placeholder array.
Anyway the code is now this...
export default (state = {}, action) => {
switch (action.type) {
case FETCH_SONGS:
return { ...state, ..._.mapKeys(action.payload, 'id') };
case CREATE_SONG:
return { ...state, [action.payload.id]: action.payload };
default:
return state;
}
}
Related
I have been able to pull data from an API that I built using MongoDB and Express, but am having trouble rendering the nested data to my React component.
For example, if I type in <p>{restaurant.cuisine}</p> I am able to retrieve Burgers, American, but if I try and access {restaurant.status.delivery}, I get an error that says:
Cannot read property 'delivery' of undefined.
But if I {console.log(restaurant.status} I can see the object? I tried turning the object into an array using Object.values, but that didn't work either.
The same thing happens if I try to access the nested objects in {restaurant.images} and {restaurant.geometry}.
Here's a copy of my React hook:
import { useReducer, useEffect } from 'react';
import axios from 'axios';
const ACTIONS = {
MAKE_REQUEST: 'make-request',
GET_DATA: 'get-data',
ERROR: 'error',
};
function reducer(state, action) {
switch (action.type) {
case ACTIONS.MAKE_REQUEST:
return { loading: true, restaurant: [] };
case ACTIONS.GET_DATA:
return {
...state,
loading: false,
restaurant: action.payload.restaurant,
};
case ACTIONS.ERROR:
return {
...state,
loading: false,
error: action.payload.error,
restaurant: [],
};
default:
return state;
}
}
export default function useFetchSingleRestaurant({ id }) {
const [state, dispatch] = useReducer(reducer, {
restaurant: [],
loading: true,
});
useEffect(() => {
dispatch({ type: ACTIONS.MAKE_REQUEST });
axios
.get('http://localhost:4444/restaurants/' + id)
.then((res) => {
dispatch({
type: ACTIONS.GET_DATA,
payload: { restaurant: res.data.restaurant },
});
})
.catch((e) => {
dispatch({
type: ACTIONS.ERROR,
payload: { error: e },
});
});
}, [id]);
return state;
}
I'm accessing it in my SingleRestaurant component:
function SingleRestaurant({ match }) {
const { restaurant } = useFetchSingleRestaurant({ id: match.params.id });
return (
<p>{restaurant.status.delivery}</p>
)
}
And then here's my backend setup as well:
showRestaurant = async (req, res) => {
const restaurant = await Restaurant.findById(req.params.id)
.populate({ path: 'reviews', populate: { path: 'author' } })
.populate('author');
if (!restaurant) {
req.flash('error', 'Restaurant not found.');
return res.redirect('/restaurants');
}
res.send({ restaurant });
};
Until your server request returns restaurant it will be set as the default [] that you have set.
An empty array does not have a property of status, so hence the error.
if you change your default to null:
const [state, dispatch] = useReducer(reducer, {
restaurant: null,
loading: true,
});
And then check for a value:
function SingleRestaurant({ match }) {
const { restaurant } = useFetchSingleRestaurant({ id: match.params.id });
if (!restaurant) return 'Loading'
return (
<p>{restaurant.status.delivery}</p>
)
}
You could also pass back the loading state from your hook and then do a check on that.
I have a fetch request used on multiple pages, and would like to turn it into a component to simply call in whenever it's needed. This is proving to be harder than I thought, and it's bring up a number of issues.
I have tried using the wrappedComponent function but not sure if that's the solution as it's still not working. It's now saying that the fetchPosts class constructor cannot be invoked without new.
const that = this;
fetch ('/testrouter')
.then (response => {
return response.json();
}).then(jsonData => {
that.setState({posts:jsonData})
}).catch(err => {
console.log('Error fetch posts data '+err)
});
}
This is what I want to turn into a component, so that I can just call it by it's name from another one inside componentDidMount. I have tried doing this:
function fetchPosts(WrappedComponent) {
class FetchPosts extends Component {
constructor(props) {
super(props)
this.state = {
posts: []
}
}
fetchAllPosts() {
const that = this;
fetch ('/testrouter')
.then (response => {
return response.json();
}).then(jsonData => {
that.setState({posts:jsonData})
}).catch(err => {
console.log('Error fetch posts data '+err)
});
}
render() {
return (<WrappedComponent
fetchAllPosts = {this.fetchAllPosts})
/>);
}
}
return FetchPosts;
}
export default fetchPosts
Then importing it and calling it with fetchPosts but it's not working.
I was hoping I would be able to create a component, add the code then import the component, but this is not working.
You might want to create a custom hook to do this:
useFetch.jsx
import React, { useState, useEffect } from 'react'
const useFetch = (url) =>
const [state, setState] = useState({ loading: true, data: null, error: null })
useEffect(() => {
fetch(url)
.then(res => res.json())
.then(data => setState(state => ({ ...state, loading: false, data }))
.catch(error => setState(state => ({ ...state, loading: false, error }))
},[])
return state
}
export default useFetch
MyComponent.jsx
import React from 'react'
import useFetch from './useFetch.jsx'
const MyComponent = () => {
const data = useFetch('/testrouter')
return (<>
{ data.loading && "Loading..." }
{ data.error && `There was an error during the fetch: {error.message}` }
{ data.data && <Posts posts={data.data}/> }
</>)
}
I'm having trouble returning an array to my React component from a fetch call from my Express server, that I set up in Redux.
I'm trying to just return the vitamins array from this json from Express:
router.get('/', function(req, res, next) {
vitamins: [
{
name: "Vitamin B2"
}
],
minerals: [
{
name: "Zinc"
}
]});
});
This is the fetch call and FETCH_VITAMINS_SUCCESS action in my actions.js.
export function fetchVitamins() {
return dispatch => {
return fetch("/users")
.then(res => res.json())
.then(micros => {
dispatch(fetchVitaminsSuccess(micros.vitamins));
return micros.vitamins;
})
};
}
export const FETCH_VITAMINS_SUCCESS = 'FETCH_VITAMINS_SUCCESS';
export const fetchVitaminsSuccess = vitamins => ({
type: FETCH_VITAMINS_SUCCESS,
payload: { vitamins }
});
This is my reducers.js where i'm trying to set the state to "micros.vitamins".
const initialState = {
micros: [],
};
function vitaminReducer(state = initialState, action) {
switch(action.type) {
case FETCH_VITAMINS_SUCCESS:
return {
...state.vitamins,
micros: action.payload
};
default:
return state;
}
}
This is my React component Vitamins.js where I'm importing fetchVitamins() and trying to pass the names of each vitamins to a menu dropdown in an option tag.
componentDidMount() {
this.props.fetchVitamins();
}
renderData() {
const { vitamins } = this.state.micros;
return vitamins.map((micro, index) => {
return (
<option value={micro.value} key={index}>{micro.name}</option>
)
})
}
render() {
return (
<select value={this.props.value}>
{this.renderData()}
</select>
)
}
const mapStateToProps = state => ({
micros: state.vitamins,
});
export default connect(mapStateToProps, { fetchVitamins })(Vitamins);
Right now I get back the error "TypeError: Cannot read property 'micros' of null", highlighting over my renderData() function.
It should be:
const { vitamins } = this.props.micros;
because you pass micros as props from redux. While you tried to access it from the state (which I guess was not initialized that's why it's null).
Another thing, you pass Object in payload:
export const fetchVitaminsSuccess = vitamins => ({
type: FETCH_VITAMINS_SUCCESS,
payload: { vitamins }
});
and set it as micros in your reducer:
switch(action.type) {
case FETCH_VITAMINS_SUCCESS:
return {
...state.vitamins,
micros: action.payload
};
However, your micros are initially an array which may lead to unexpected errors. Maybe you should change your initial state to something resembling the response like:
const initialState = {
micros: {
vitamins: []
},
};
This way const { vitamins } = this.state.micros; will always return some array - before and after the response.
I'm trying to fetch data from my Express server in Redux, and mapping over the object to just use one array, called "vitamins". This is the json object.
router.get('/', function(req, res, next) {
vitamins: [
{
name: "Vitamin B2"
}
],
minerals: [
{
name: "Zinc"
}
]});
});
This is my action.js, where I'm creating the function fetchVitamins() to just fetch micros.vitamins.
export function fetchVitamins() {
return dispatch => {
return fetch("/users")
.then(res => res.json())
.then(micros => {
dispatch(fetchVitaminsSuccess(micros.vitamins));
return micros.vitamins;
})
};
}
export const FETCH_VITAMINS_SUCCESS = 'FETCH_VITAMINS_SUCCESS';
export const fetchVitaminsSuccess = vitamins => ({
type: FETCH_VITAMINS_SUCCESS,
payload: { vitamins }
});
This is my reducers.js
const initialState = {
micros: [],
};
function vitaminReducer(state = initialState, action) {
switch(action.type) {
case FETCH_VITAMINS_SUCCESS:
return {
...state,
micros: action.payload.vitamins
};
default:
return state;
}
}
This is my React component Vitamins.js where I'm importing fetchVitamins() and trying to pass the names of each vitamins to a menu dropdown in an option tag.
componentDidMount() {
this.props.dispatch(fetchVitamins());
}
renderData() {
const { vitamins } = this.state.micros;
return vitamins.map((micro, index) => {
return (
<option value={micro.value} key={index}>{micro.name}</option>
)
})
}
render() {
return (
<select value={this.props.value}>
{this.renderData()}
</select>
)
}
const mapStateToProps = state => ({
micros: state.micros.vitamins,
});
Right now when it renders, I get this error: "TypeError: Cannot read property 'vitamins' of undefined", highlighting over "micros: state.micros.vitamins,".
Am I calling and setting state correctly? If I set my initialState to micros: [], then setting the state to "state.micros.vitamins" should work, I thought.
because of you get the server data n vitamins objects so that data should be in vitamins:[], in that Format so that why state.macros.vitamins work.
I not undestand everything with javascript etc, I want to get my data returned by ma action redux but i'have a problem with my code.
const mapStateToProps = state => {
const group = state.groupReducer.group ? state.groupReducer.group : [ ]
return {
group
}
how i can get my data ?
When I try with that:
const mapStateToProps = state => {
const group = state.groupReducer.group.data.data[0] ? state.groupReducer.group.data.data[0] : [ ]
return {
group
}
And my goal is map around group
renderGroup = group => {
return group.map((groups => {
<div key={groups.data.data.id}>
//
</div>
}))
}
Sagas.js
export function* loadApiDataGroup() {
try {
// API
const response = yield
call(axios.get,'http://localhost:8000/api/group');
yield put(loadGroup(response))
} catch (e) {
console.log('REQUEST FAILED! Could not get group.')
console.log(e)
}
}
Action.js
export function loadGroup(data){ return { type: LOAD_GROUP, data }};
export function creatGroup(data){ return { type: CREATE_GROUP, data}};
// reducer
export default function groupReducer( state= {}, action = {}){
switch (action.type){
case LOAD_GROUP:
return {
...state,
group: action.data
}
case CREATE_GROUP:
return {
...state
}
default:
return state
}
thank you to help me
Try
const mapStateToProps = state => ({
group: state.groupReducer.group || []
});
Then you can use this.props.group in the component. Even though you might only want one thing in mapStateToProps, it's usually not directly returned like that.
If group is the response of an API request, you need to unpack data first, this is done in your async action creator (you will want to use redux-thunk or something similar):
const getGroup = () => async (dispatch) => {
dispatch({ type: 'GET_GROUP_REQUEST' });
try {
const { data } = await axios.get('/some/url');
dispatch({ type: 'GET_GROUP_SUCCESS', payload: data });
} catch (error) {
dispatch({ type: 'GET_GROUP_FAILURE', payload: error });
}
};