Am fetching data from an api
this is the action in store
fetchVisits({commit}) {
axios.get('/api/visits')
.then(res => {
commit('FETCH_VISITS', res.data)
}).catch(err => {
console.log(err)
})
},
}
mutation
FETCH_VISITS(state, visits) {
return state.visits = visits
},
state
state: {
visits:[]
},
getter
getters: {
visits: state => {
return state.visits
}
},
dispatched action
created() {
this.$store.dispatch('fetchVisits')
},
But when i refresh the page the data to be displayed disappears
Actions are triggered with the store.dispatch method. Now in your case you might missed to dispatch the fetchVisit action or possible also, you dispatched that action in your other component which is not your main component. That's why when you hit reload the dispatch method was not invoke. To solve that .
You have to dispatch the fetchVisit action in your main component to invoke it every time you reload the page. Or, you dispatch again that action to the component itself which you said the state is empty. This is how you dispatch
this.store.dispatch('fetchVisits')
Related
I have a situation where I should get a song item by id to get the path for that song, and then navigate to that song on button click.
Is there any specific hook that can be used to navigate on data arrival, useEffect will be called any time that state changes but the problem is that first needs to be dispatched the action to get the song, check if it returns any item and then navigate. Typically if it is has been published on the list, it should exist on the db, but the problem might be at the API side, so that check results.length > 0 is why that check is necessary.
useEffect(() => {
const handleClick = (myId: string) => {
dispatch(SongActions.searchSong(myId));
if (results.length > 0) {
if (Object.keys(results[0]).length > 0) {
// navigate(`/songs/${results[0].myPath}`);
}
}
}
}, [dispatch, results])
When user clicks on list item which has a song title, it should call the function handleClick(id) with id of the song as parameter, that is to get the metadata of the song, src path etc.
<Typography onClick={() => handleClick(songItem.songId)} sx={styles.songListItemText}>{songItem.Title}</Typography>
Edit
And this is how I have setup the searchSong action:
searchSong: (obj: SearchSongInputModel): AppThunk<SearchPayload> => async (dispatch) => {
dispatch({
payload: { isLoading: true },
type: SearchActionType.REQUEST,
});
try {
const response = await SearchApi.searchSongAsync(obj);
if (response.length === 0) {
toast.info(`No data found: ${obj.SongId}`)
}
dispatch({
type: SearchActionType.RECEIVED_SONG,
payload: { results: response },
});
} catch (e) {
console.error("Error: ", e);
}
}
You appear to be mixing up the purpose of the useEffect hook and asynchronous event handlers like button element's onClick handlers. The useEffect hook is to meant to issue intentional side-effects in response to some dependency value updating and is tied to the React component lifecycle, while onClick handlers/etc are meant to respond to asynchronous events, i.e. a user clicking a button. They don't mix.
Assuming SongActions.searchSong is an asynchronous action, you've correctly setup Redux middleware to handle them (i.e. Thunks), and the action returns the fetched response data, then the dispatched action returns a Promise that the callback can wait for.
Example:
const navigate = useNavigate();
const dispatch = useDispatch();
const handleClick = async (myId: string) => {
const results = await dispatch(SongActions.searchSong(myId));
if (results.length > 0 && Object.keys(results[0]).length > 0) {
navigate(`/songs/${results[0].myPath}`);
}
};
...
<Typography
onClick={() => handleClick(songItem.songId)}
sx={styles.songListItemText}
>
{songItem.Title}
</Typography>
The searchSong action creator should return a resolved value for consumers to await for.
searchSong: (obj: SearchSongInputModel): AppThunk<SearchPayload> => async (dispatch) => {
dispatch(startRequest());
try {
const results = await SearchApi.searchSongAsync(obj);
if (!results.length) {
toast.info(`No data found: ${obj.SongId}`)
}
dispatch(receivedSong({ results }));
return results; // <-- return resolved value here
} catch (e) {
console.error("Error: ", e);
} finally {
dispatch(completeRequest());
}
}
You can create a state such as const [isDataPresent, setIsDataPresent] = useState(false) to keep track of if the data has arrived or not. And as David has mentioned in the comments you cannot call the function inside the useEffect on handleClick. Instead what you can do is create that function outside the useEffect hook and inside the same function you fetch the data and check if the data is at all present, if present then you can set the above boolean state to true and then redirect from that function itself.
Since you are already fetching the data from the same API and different endpoint, what you can do is -
Create a new component.
Since you are mapping over the data send the data to this component by rendering it inside the map function. It'd allow the data to be passed and components to be rendered one by one.
Create a state in the new component.
Use useEffect hook to fetch the data for a single song since when you are passing the data from the previous component to this one you would also get access to the ID and store it inside the state. This would be occurring inside the newly created component.
I'm trying to write a custom hook that uses useQuery from react-query. The custom hook takes in the id of an employee and fetches some data and returns it to the consuming component. I want to be able to dispatch a redux action to show a loading indicator or show an error message if it fails. Here is my custom hook.
export default function useEmployee(id) {
const initial = {
name: '',
address: '',
}
const query = useQuery(['fetchEmployee', id], () => getEmployee(id), {
initialData: initial,
onSettled: () => dispatch(clearWaiting()),
onError: (err) => dispatch(showError(err)),
})
if (query.isFetching || query.isLoading) {
dispatch(setWaiting())
}
return query.data
}
When I refresh the page, I get this error in the browser's console and I'm not sure how to fix this error?
Warning: Cannot update a component (`WaitIndicator`) while rendering a different component (`About`).
To locate the bad setState() call inside `About`, follow the stack trace as described in
The issue is likely with dispatching the setWaiting action outside any component lifecycle, i.e. useEffect. Move the dispatch logic into a useEffect hook with appropriate dependency.
Example:
export default function useEmployee(id) {
const initial = {
name: '',
address: '',
};
const { data, isFetching, isLoading } = useQuery(['fetchEmployee', id], () => getEmployee(id), {
initialData: initial,
onSettled: () => dispatch(clearWaiting()),
onError: (err) => dispatch(showError(err)),
});
useEffect(() => {
if (isFetching || isLoading) {
dispatch(setWaiting());
}
}, [isFetching, isLoading]);
return data;
}
I have two reducer actions that I want to dispatch one after the other. The first one modifies the state, then the second one uses a portion of the modified state to make another modification. The difficulty is that when the second dispatch is called, it still has the old outdated state and thus doesn't update the state properly.
An example is the following (also found here - https://codesandbox.io/s/react-usereducer-hqtc2) where there is a list of conversations along with a note of which one is considered the "active" conversation:
import React, { useReducer } from "react";
const reducer = (state, action) => {
switch (action.type) {
case "removeConversation":
return {
...state,
conversations: state.conversations.filter(
c => c.title !== action.payload
)
};
case "setActive":
return {
...state,
activeConversation: action.payload
};
default:
return state;
}
};
export default function Conversations() {
const [{ conversations, activeConversation }, dispatch] = useReducer(
reducer,
{
conversations: [
{ title: "James" },
{ title: "John" },
{ title: "Mindy" }
],
activeConversation: { title: "James" }
}
);
function removeConversation() {
dispatch({ type: "removeConversation", payload: activeConversation.title });
dispatch({ type: "setActive", payload: conversations[0] });
}
return (
<div>
Active conversation: {activeConversation.title}
<button onClick={removeConversation}>Remove</button>
<ul>
{conversations.map(conversation => (
<li key={conversation.title}>{conversation.title}</li>
))}
</ul>
</div>
);
}
In here, when I click the "remove conversation" button, I want to remove the active conversation, then set the active conversation to be the one at the top of the list. However, here when the first dispatch removes the conversation from the list, the second dispatch sets active to conversations[0], which still contains the removed value (since the state hasn't updated yet). As a result, it keeps the active conversation as the one it was before, even though it's been removed from the list.
I could probably combine the logic into just one action and do it all there (remove the conversation and set active all in one), but I would ideally like to keep my reducer actions to have one responsibility each if possible.
Is there any way to make the second dispatch call have the most recent version of the state so that this kind of problem doesn't occur?
It may help if you think of useEffect() like setState's second parameter (from class based components).
If you want to do an operation with the most recent state, use useEffect() which will be hit when the state changes:
const {
useState,
useEffect
} = React;
function App() {
const [count, setCount] = useState(0);
const decrement = () => setCount(count-1);
const increment = () => setCount(count+1);
useEffect(() => {
console.log("useEffect", count);
}, [count]);
console.log("render", count);
return (
<div className="App">
<p>{count}</p>
<button onClick={decrement}>-</button>
<button onClick={increment}>+</button>
</div>
);
}
const rootElement = document.getElementById("root");
ReactDOM.render( < App / > , rootElement);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.8.6/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.8.6/umd/react-dom.production.min.js"></script>
<div id="root"></div>
Some further info on useEffect()
Answering this for anyone who may come across similar issues in the future. The key to finding the solution to this is understanding that state in React is a snapshot.
You can see that in the dispatched setActive action, the value of conversations[0] of state is being passed:
dispatch({ type: "setActive", payload: conversations[0] });
Thus when the action is called before the next render, it uses the snapshotted state at the time of re-render:
// snapshot of state when action is called
{
conversations: [
{ title: "James" },
{ title: "John" },
{ title: "Mindy" }
],
activeConversation: { title: "James" }
}
Thus conversations[0] evaluates to {title: "James"}. This is why in the reducer, activeConversation: action.payload returns {title: "James"} and the active conversation doesn't change. In technical terms, "you're calculating the new state from the value in your closure, instead of calculating it from the most recent value."
So how do we fix this? Well useReducer actually in fact always has access to the most recent state value. It is a sister pattern to the state updater function, which also gives you access to the latest state variable even before the next render.
This means that after the first dispatch action:
dispatch({ type: "removeConversation", payload: activeConversation.title }); // first dispatch action
dispatch({ type: "setActive", payload: conversations[0] }); // second dispatch action
the next dispatch action actually has access to the latest state already. You just need to access it:
case "setActive":
return {
...state,
activeConversation: state.conversations[0]
};
You can verify this by logging it to the console:
const reducer = (state, action) => {
console.log(state);
switch (action.type) {
case "removeConversation":
return {
...state,
conversations: state.conversations.filter(
c => c.title !== action.payload
)
};
case "setActive":
return {
...state,
activeConversation: state.conversations[0]
};
default:
return state;
}
};
Also important to note that the 2 dispatch calls are batched as explained in the state updater function link mentioned above. More info on batching here too.
Vuex allows us to write plugins that do something whenever a mutation is committed. Is there any way to have a similar functionality, but with actions?
I notice you can "enhance" actions like the vuexfire library does, is this the best way to do so?
My goal is to have some way to track if/how many ajax calls are currently pending, and automatically show some kind of animation based on that number.
Edit: To clarify, I am wondering if there is a way to do this using just Vuex, without pulling into additional libraries.
As of Vuex v2.5 you can call subscribeAction to register a callback function which will be called after each dispatched action in the store.
The callback will receive an action descriptor (object with type and payload properties) as its first argument and the store's state as the second argument.
The documentation for this is on the Vuex API Reference page.
For example:
const store = new Vuex.Store({
plugins: [(store) => {
store.subscribeAction((action, state) => {
console.log("Action Type: ", action.type)
console.log("Action Payload: ", action.payload)
console.log("Current State: ", state)
})
}],
state: {
foo: 1
},
mutations: {
INCREASE_FOO(state) {
state.foo++;
},
},
actions: {
increaseFoo({ commit }) {
commit('INCREASE_FOO');
}
}
});
new Vue({
el: '#app',
store,
methods: {
onClick() {
this.$store.dispatch('increaseFoo');
}
}
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.2/vue.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vuex/3.0.1/vuex.min.js"></script>
<div id="app">
Foo state: {{ $store.state.foo }}
<button #click="onClick">Increase Foo</button>
</div>
Since 3.1.0, subscribeAction can also specify whether the subscribe handler should be called before or after an action dispatch (the default behavior is before):
store.subscribeAction({
before: (action, state) => {
console.log(`before action ${action.type}`)
},
after: (action, state) => {
console.log(`after action ${action.type}`)
}
})
documentation: https://vuex.vuejs.org/api/#subscribeaction
I recently started migrating things from jQ to a more structured framework being VueJS, and I love it!
Conceptually, Vuex has been a bit of a paradigm shift for me, but I'm confident I know what its all about now, and totally get it! But there exist a few little grey areas, mostly from an implementation standpoint.
This one I feel is good by design, but don't know if it contradicts the Vuex cycle of uni-directional data flow.
Basically, is it considered good practice to return a promise(-like) object from an action? I treat these as async wrappers, with states of failure and the like, so seems like a good fit to return a promise. Contrarily mutators just change things, and are the pure structures within a store/module.
actions in Vuex are asynchronous. The only way to let the calling function (initiator of action) to know that an action is complete - is by returning a Promise and resolving it later.
Here is an example: myAction returns a Promise, makes a http call and resolves or rejects the Promise later - all asynchronously
actions: {
myAction(context, data) {
return new Promise((resolve, reject) => {
// Do something here... lets say, a http call using vue-resource
this.$http("/api/something").then(response => {
// http success, call the mutator and change something in state
resolve(response); // Let the calling function know that http is done. You may send some data back
}, error => {
// http failed, let the calling function know that action did not work out
reject(error);
})
})
}
}
Now, when your Vue component initiates myAction, it will get this Promise object and can know whether it succeeded or not. Here is some sample code for the Vue component:
export default {
mounted: function() {
// This component just got created. Lets fetch some data here using an action
this.$store.dispatch("myAction").then(response => {
console.log("Got some data, now lets show something in this component")
}, error => {
console.error("Got nothing from server. Prompt user to check internet connection and try again")
})
}
}
As you can see above, it is highly beneficial for actions to return a Promise. Otherwise there is no way for the action initiator to know what is happening and when things are stable enough to show something on the user interface.
And a last note regarding mutators - as you rightly pointed out, they are synchronous. They change stuff in the state, and are usually called from actions. There is no need to mix Promises with mutators, as the actions handle that part.
Edit: My views on the Vuex cycle of uni-directional data flow:
If you access data like this.$store.state["your data key"] in your components, then the data flow is uni-directional.
The promise from action is only to let the component know that action is complete.
The component may either take data from promise resolve function in the above example (not uni-directional, therefore not recommended), or directly from $store.state["your data key"] which is unidirectional and follows the vuex data lifecycle.
The above paragraph assumes your mutator uses Vue.set(state, "your data key", http_data), once the http call is completed in your action.
Just for an information on a closed topic:
you don’t have to create a promise, axios returns one itself:
Ref: https://forum.vuejs.org/t/how-to-resolve-a-promise-object-in-a-vuex-action-and-redirect-to-another-route/18254/4
Example:
export const loginForm = ({ commit }, data) => {
return axios
.post('http://localhost:8000/api/login', data)
.then((response) => {
commit('logUserIn', response.data);
})
.catch((error) => {
commit('unAuthorisedUser', { error:error.response.data });
})
}
Another example:
addEmployee({ commit, state }) {
return insertEmployee(state.employee)
.then(result => {
commit('setEmployee', result.data);
return result.data; // resolve
})
.catch(err => {
throw err.response.data; // reject
})
}
Another example with async-await
async getUser({ commit }) {
try {
const currentUser = await axios.get('/user/current')
commit('setUser', currentUser)
return currentUser
} catch (err) {
commit('setUser', null)
throw 'Unable to fetch current user'
}
},
Actions
ADD_PRODUCT : (context,product) => {
return Axios.post(uri, product).then((response) => {
if (response.status === 'success') {
context.commit('SET_PRODUCT',response.data.data)
}
return response.data
});
});
Component
this.$store.dispatch('ADD_PRODUCT',data).then((res) => {
if (res.status === 'success') {
// write your success actions here....
} else {
// write your error actions here...
}
})
TL:DR; return promises from you actions only when necessary, but DRY chaining the same actions.
For a long time I also though that returning actions contradicts the Vuex cycle of uni-directional data flow.
But, there are EDGE CASES where returning a promise from your actions might be "necessary".
Imagine a situation where an action can be triggered from 2 different components, and each handles the failure case differently.
In that case, one would need to pass the caller component as a parameter to set different flags in the store.
Dumb example
Page where the user can edit the username in navbar and in /profile page (which contains the navbar). Both trigger an action "change username", which is asynchronous.
If the promise fails, the page should only display an error in the component the user was trying to change the username from.
Of course it is a dumb example, but I don't see a way to solve this issue without duplicating code and making the same call in 2 different actions.
actions.js
const axios = require('axios');
const types = require('./types');
export const actions = {
GET_CONTENT({commit}){
axios.get(`${URL}`)
.then(doc =>{
const content = doc.data;
commit(types.SET_CONTENT , content);
setTimeout(() =>{
commit(types.IS_LOADING , false);
} , 1000);
}).catch(err =>{
console.log(err);
});
},
}
home.vue
<script>
import {value , onCreated} from "vue-function-api";
import {useState, useStore} from "#u3u/vue-hooks";
export default {
name: 'home',
setup(){
const store = useStore();
const state = {
...useState(["content" , "isLoading"])
};
onCreated(() =>{
store.value.dispatch("GET_CONTENT" );
});
return{
...state,
}
}
};
</script>