So I have this state for handling error messages and that state have two actions
The first one for setting the message:
export const setNotification = (message) => {
return {
type: "SET_NOTIFICATION",
data: {
message,
visibility: "visible"
}
}
}
And the second for removing the message after 5 seconds:
export const clearNotification = (seconds=5) => {
setTimeout(()=> { return {
type: "REMOVE_NOTIFICATION",
data: {
message: "",
visibility: "hidden"
}
}}, seconds * 1000)
}
And when calling the second function called ClearNotification I get this error:
Error: Actions must be plain objects. Use custom middleware for async actions.
Why am I getting this message and how can I fix it?
Thanks.
That's because you can not return a function as action. The actions are simple objects of the shape ´{type: string, ...any}´. If you want to return a function you should google for redux-thunk or something like redux-saga or redux-observable but those are quite tricky.
This link has an example of what you want to do. https://github.com/reduxjs/redux-thunk#motivation
Related
I have a Vue component called aui-button that is used like:
<aui-button classes="btn-primary test-class" :callback="test">Test Button</aui-button>
I'm trying to design the component to be able to run any given callback without the callback requiring any structural changes or special return values; basically, I want to just give it some code, and have it run it. I pass the callback as a prop and call it. Easy.
props: ['classes', 'callback'],
methods: {
runCallback() {
this.callback();
}
}
What I'm stuck on is how to change the state data of the button based on the callback given those constraints.
data: function() {
return {
loading: false
}
},
How can I change the value of a specific data value on the component after callback execution given that I'd like to have zero say over what the callback argument is doing? Ideally these have a wide array of uses, from API calls to simple value changes.
Here's another answer in response to your comment. If you really wanted to implement it that way then there's nothing stopping you.
The problem is that the callback will be asynchronous (otherwise, what's the point of setting a loading state), so the component needs to be told when the asynchronous callback has completed.
You could define your callback functions so that they take a done() callback.
AuiButton.vue
props: ['classes', 'callback'],
data() { return { loading: false}},
methods: {
runCallback() {
this.loading = true;
this.callback(this.doneCallback);
},
doneCallback() {
this.loading = false;
},
},
Parent Component
<aui-button classes="btn-primary test-class" :callback="test">Test Button</aui-button>
...
methods: {
test(doneCallback) {
doSometingAsync(someData, (error, result) => {
doneCallback();
// do something with result..
})
},
Perhaps a better solution is to use events, but give the click event a done callback:
AuiButton.vue
props: ['classes'], // don't need to pass the callback as a prop anymore.
data() { return { loading: false}},
methods: {
runCallback() {
this.loading = true;
this.$emit('click', this.doneCallback);
},
doneCallback() {
this.loading = false;
},
},
Parent Component
<aui-button classes="btn-primary test-class" #click="test">Test Button</aui-button>
...
methods: {
test(doneCallback) {
doSometingAsync(someData, (error, result) => {
doneCallback();
// do something with result..
})
},
Rather than pass a callback to your button component, it is recommended practice to make your component $emit an event to the parent. The parent can then run whatever code it wants in the event handler.
Then, you should pass a loading prop to your component to control its loading state. e.g:
AuiButton.vue
<button :classes="classes" :disabled="loading" #click="$emit('click') ...>
...
props: {
classes: String,
loading: {
type: Boolean,
default: false
},
Parent component
<aui-button classes="btn-primary test-class" :loading="loading" #click="buttonClick">
Test Button
</aui-button>
...
data() { return {
loading: false,
} },
methods: {
buttonClick() {
this.loading = true;
doSometingAsync(someData, (error, result) => {
this.loading = false;
// do something with result..
})
},
Now your button component doesn't need to do anything clever - it's told whether it should be in the loading state and it tells its parent whenever it is clicked.
I'm using a variable twice within a function but it returns different values even though I'm making no modifications to it.
This is happening within a form component developed with Vue.js (v2) which dispatches a Vuex action. I think this has nothing to do with Vue/Vuex per se, but it's important to understand part of the code.
Here is the relevant piece of code from my component
import { mapActions } from 'vuex'
export default {
data() {
return {
product: {
code: '',
description: '',
type: '',
productImage: [],
productDocs: {},
}
}
},
methods: {
...mapActions(['event']),
save() {
console.log("this.product:", this.product)
const valid = this.$refs.form.validate() // this validates the form
console.log("this.product:", this.product)
if (valid) {
try {
this.event({
action: 'product/addProduct',
data: this.product
})
}
finally {
this.close()
}
}
},
// other stuff
and a small piece of code for the vuex action "event"
event: async ({ dispatch }, event) => {
const time = new Date()
const evid = `${Date.now()}|${Math.floor(Math.random()*1000)}`
console.log(`Preparing to dispatch... Action: ${event.action} | data: ${JSON.stringify(event.data)} | Event ID: ${evid}`)
// enriching event
event.evid = evid;
event.timestamp = time;
event.synced = 0
// Push user event to buffer
try {
await buffer.events.add(event)
} catch (e) {
console.log(`Error writing event into buffer. Action ${event.action} | evid: ${evid} `)
}
// dispatch action
try {
await dispatch(event.action, event)
}
catch (err) {
console.log(`Error dispatching action: ${event.action} | data: ${event.data}\n${err.stack || err}`)
window.alert('Could not save. Try again. \n' + err + `\n Action: ${event.action} | data: ${event.data}`)
}
},
The problem is with this.product. I've placed the several console.log to check out the actual values because it wasn't working as expected. The logs from the save() functions return undefined, but within the event function (a vuex action) the values are as expected, as shown in the console logs:
When I log this.product in the save() function. Both logs are the same.
When I log the event in the vuex action, it shows that event.data is actually the product.
I must be doing something terribly wrong here, but I'm totally blind to it. Any help is appreciated.
#Sumurai8: thanks for editing the question and for the hint.
Part of this may be because of that tiny i next to the opened product.
If you hover over it, it says that "the object has been evaluated just
now", which means it evaluates what is in the object when you open the
object, which is way after executing the action. [...] Whatever is
changing the product may very well happen after the event somewhere.
It actually helped me find the solution.
Basically within the this.close function called in the finally statement of the save() function, I was resetting the form and thus this.product, which was used solely to hold the form data. So at evaluation time, the object had undefined properties, while the event function managed to output to the console before the reset. However at the end the store would not get updated as expected (that's how I noticed the issue), because the event function and the action called within it are asynchronous and so the value got reset before the actual mutation of the vuex store.
Logging JSON.stringify(this.product) outputted the right value even within the save() method. I used that to create a more robust copy of the data and passed that to the event function as follows:
this.event({
action: 'product/addProduct',
data: JSON.parse(JSON.stringify(this.product))
})
Now everything works like a charme.
I'm finding a solution to async computed method in Components:
Currently, my component is:
<div class="msg_content">
{{messages}}
</div>
<script>
export default {
computed: {
messages: {
get () {
return api.get(`/users/${this.value.username}/message/`, {'headers': { 'Authorization': 'JWT ...' }})
.then(response => response.data)
}
}
},
}
</script>
Result:
{}
How to rewrite it in Promise mode? Because I think we can async computed by writing into Promise mode.
Computed properties are basically functions that cache their results so that they don't have to be calculated every time they are needed. They updated automatically based on the reactive values they use.
Your computed does not use any reactive items, so there's no point in its being a computed. It returns a Promise now (assuming the usual behavior of then).
It's not entirely clear what you want to achieve, but my best guess is that you should create a data item to hold response.data, and make your api.get call in the created hook. Something like
export default {
data() {
return {
//...
messages: []
};
},
created() {
api.get(`/users/${this.value.username}/message/`, {
'headers': {
'Authorization': 'JWT ...'
}
})
.then(response => this.messages = response.data);
}
}
es7 makes doing this quite trivial by using async and await in conjunction with axios' returned promise. You'll need the vue-async-computed package.
export default {
asyncComputed: {
async myResolvedValue() {
return await api.get(`/users/${this.value.username}/message/`, {'headers': { 'Authorization': 'JWT ...' }})
.then(response => response.data)
}
}
}
I bumped on a similar case where I need to re-run the computed function to fetch from a server every time a data or a props changes.
Without installing any extra package (vue-async-computed or vue3-async-computed as pointed by other answers), you can force a data to reload by creating a "virtual" computed method.
Lets say you want to fetch data from the server every time the user types their username, and depending on what was typed, you want to show a given message from the server.
From the example below, username and messages in this case are both reactive data, but there is no direct connection between them, so lets create a computed that depends on username by returning its value, which will force it to be called every time username is changed. Now you just need to call a function that can be async and will update messages after fetching from the server.
In the example below, I use ":dummy" just to force a call to my computed function.
<template>
<input v-model="username">
<div class="msg_content" :dummy="force_react">
{{messages}}
</div>
</template>
<script>
export default {
data: function () {
return {
messages: "",
username: "",
};
},
computed: {
force_react: function() {
this.get(); // called every time that this.username updates
return this.username; // becase its result depends on username
}
},
methods: {
async get() { // get's called every time that this.username updates
console.log("Got called");
let response = await api.get(`/users/${this.username}/message/`, {'headers': { 'Authorization': 'JWT ...' }});
this.messages = response.data;
}
},
}
</script>
You can see a working example here in Vue SFC playground
Why not using a watcher? Vue Documentation
You can use async function in the callback of the watcher.
I have created a react-redux application. Currently what it does is load courses from the server(api), and displays them to the course component. This works perfectly. I'm trying to add a feature where you can create a course by posting it to the server, the server would then true an a success object. However, when i post to the server i get the following error(see below). I think this is due to my connect statement listening for the load courses action. Clearly its thinking it should be getting a list of something, instead of a success object. I have tried a few thing for it to listen for both courses and the success response, but to save you the time of reading all the strange thing i have done, i could not get it to work. Dose anyone know how to fix this issue ?
error
TypeError: this.props.courses.map is not a function
course.component.js
onSave(){
// this.props.createCourse(this.state.course);
this.props.actions.createCourse(this.state.course);
}
render() {
return (
<div>
<div className="row">
<h2>Couses</h2>
{this.props.courses.map(this.courseRow)}
<input
type="text"
onChange={this.onTitleChange}
value={this.state.course.title} />
<input
type="submit"
onClick={this.onSave}
value="Save" />
</div>
</div>
);
}
}
// Error occurs here
function mapStateToProps(state, ownProps) {
return {
courses: state.courses
};
}
function mapDispatchToProps(dispatch) {
return {
actions: bindActionCreators(courseActions, dispatch)
};
}
export default connect(mapStateToProps, mapDispatchToProps)(Course);
course.actions.js
export function loadCourse(response) {
return {
type: REQUEST_POSTS,
response
};
}
export function fetchCourses() {
return dispatch => {
return fetch('http://localhost:3000/api/test')
.then(data => data.json())
.then(data => {
dispatch(loadCourse(data));
}).catch(error => {
throw (error);
});
};
}
export function createCourse(response) {
return dispatch => {
return fetch('http://localhost:3000/api/json', {
method: 'POST',
headers: {
'Accept': 'application/json',
'Content-Type': 'application/json'
},
body: JSON.stringify({
response: response
})
})
.then(data => data.json())
.then(data => {
dispatch(loadCourse(data));
}).catch(error => {
throw (error);
});
};
}
course.reducer.js
export default function courseReducer(state = [], action) {
switch (action.type) {
case 'REQUEST_POSTS':
return action.response;
default:
return state;
}
}
server.js
router.get('/test', function(req, res, next) {
res.json(courses);
});
router.post('/json', function(req, res, next) {
console.log(req.body);
res.json({response: 200});
});
i have tried added a response to the state, and listening for it in the map state to props, but still for some reason react is trying to map response to courses. Do i need a second connect method?
function mapStateToProps(state, ownProps) {
return {
courses: state.courses,
resposne: state.resposne
};
}
As you can see from the pictures response is getting mapped as courses and not as response.
Picture
Assumptions:
state.courses is initially an empty array - from course.reducer.js
You don't call fetchCourses() action the first time you are rendering your view
Even if you call fetchCourses() there is no problem as long as courses in server.js is an array (the array in the response replaces the initial state.courses)
Flow:
Now I assume the first render is successful and React displays the <input type="text"> and submit button. Now when you enter the title and click on the submit button, the onSave() method triggers the createCourse() action with parameter that is more or less similar to { title: 'something' }.
Then you serialize the above mentioned param and send to the server (in course.actions.js -> createCourse()) which in turn returns a response that looks like {response: 200} (in server.js). Response field is an integer and not an array! Going further you call loadCourses() with the object {response: 200} which triggers the courseReducer in course.reducer.js
The courseReducer() replaces state.courses (which is [] acc. to assumption) with an integer. And this state update triggers a re-render and you end up calling map() on an integer and not on an array, thus resulting in TypeError: this.props.courses.map is not a function.
Possible Solution:
Return a valid response from serve.js (i.e. return the course object the endpoint is called with), or
Update your reducer to add the new course object into the existing state.courses array, like, return [...state, action.response]
Update:
Based on OP's comment, if what you want to do is send the new course object to the server, validate it and send success (or error) and based on response add the same course object to the previous list of courses, then you can simply call loadData() with the same course object you called createCourse() with and (as mentioned above) inside your reducer, instead of replacing or mutating the old array create a new array and append the course object to it, in es6 you can do something like, return [...state, course].
Update 2:
I suggest you go through Redux's Doc. Quoting from Redux Actions' Doc
Actions are payloads of information that send data from your application to your store. They are the only source of information for the store.
The createCourse() action is called with a payload which is more-or-less like,
{title: 'Thing you entered in Text Field'}, then you call your server with an AJAX-request and pass the payload to the server, which then validates the payload and sends a success (or error) response based on your logic. The server response looks like, {response: 200}. This is end of the createCourse()action. Now you dispatch() loadCourses() action from within createCorse(), with the response you received from the server, which is not what you want (based on your comments). So, instead try dispatch()ing the action like this (try renaming response param, it's a bit confusing)
//.....
.then(data => {
dispatch(loadCourse(response)); // the same payload you called createCourse with
})
//.....
Now, loadCourse() is a very basic action and it simply forwards the arguments, which Redux uses to call your reducer. Now, in case you followed the previous discussion and updates how you call loadCourse(), then the return from loadCourse() looks like
{
type: REQUEST_POSTS,
response: {
title: 'Thing you entered in Text Field',
}
}
which is then passed onto your reducer, specifically your courseReducer().
Again quoting from Redux Reducers' Doc
Actions describe the fact that something happened, but don't specify how the application's state changes in response. This is the job of reducers.
The reducer must define the logic on how the action should impact the data inside the store.
In your courseReducer(), you simply returns the response field inside the action object and [expect] Redux to auto-magically mutate your state! Unfortunately this is not what happens :(
Whatever you return from the reducer, completely replaces whatever thing/object was there before, like, if your state looks like this
{ courses: [{...}, {...}, {...}] }
and you return something like this from your reducer
{ title: 'Thing you entered in Text Field'}
then redux will update the state to look like
{ courses: { title: 'Thing you entered in Text Field'} }
state.courses is no longer an Array!
Solution:
Change your reducer to something like this
export default function courseReducer(state = [], action) {
switch (action.type) {
case 'REQUEST_POSTS':
return [...state, action.response]
default:
return state
}
}
Side Note: This is may be confusing at times, so just for the sake of record, state inside courseReducer() is not the complete state but a property on the state that the reducer manages. You can read more about this here
--Edit after reading a comment of you in a different answer, I've scraped my previous answer--
What you're currently doing with your actions and reducers, is that you're calling loadCourse when you fetched the initial courses. And when you created a new course, you call loadCourse too.
In your reducer you're directly returning the response of your API call. So when you fetch all the courses, you get a whole list of all your courses. But if you create a new one you currently receive an object saying response: 200. Objects don't have the map function, which explains your error.
I would suggest to use res.status(200).json() on your API and switching the response status in your front-end (or using then and catch if you can validate the response status, axios has this functionality (validateStatus)).
Next I would create a separate action-type for creating posts and dispatch that whenever it's successful.
I would change your reducer to something like
let initialState = {
courses: [],
createdCourse: {},
}
export default (state = initialState, action) => {
switch (action.type) {
case 'REQUEST_POSTS':
return {
...state,
courses: action.response
}
case 'CREATE_COURSE_SUCCESS':
return {
...state,
createdCourse: action.response,
}
default: return state;
}
}
I wouldn't mind looking into your project and giving you some feedback on how to improve some things (ES6'ing, best practices, general stuff)
Based on the questions & answers so far, it looks like you need to do something like this:
1) Add a new action and dispatch this from your createCourse function
export function courseAdded(course, response) {
return {
type: 'COURSE_ADDED',
course
response
};
}
export function createCourse(course) {
return dispatch => {
return fetch('http://localhost:3000/api/json', {
method: 'POST',
headers: {
'Accept': 'application/json',
'Content-Type': 'application/json'
},
body: JSON.stringify({
course
})
})
.then(response => response.json())
.then(response => {
dispatch(courseAdded(course, response));
}).catch(error => {
throw (error);
});
};
}
2) Change your reducers to handle both fetching courses and adding a new course (we're using combineReducers to handle this here)
import { combineReducers } from "redux";
function response(state = null, action) {
switch (action.type) {
case 'COURSE_ADDED':
return action.response;
default:
return state;
}
}
function courses(state = [], action) {
switch (action.type) {
case 'COURSE_ADDED':
return [...state, action.course];
case 'REQUEST_POSTS':
return action.response;
default:
return state;
}
}
export default combineReducers({
courses,
response
});
3) Hook up to the new response state in your connect component
function mapStateToProps(state, ownProps) {
return {
courses: state.courses,
response: state.response
};
}
4) Do something with this new response prop in your component if you want to show it e.g.
// this is assuming response is a string
<span className="create-course-response">
Create Course Response - {this.props.response}
</span>
UPDATE
I've added support for adding the new course to the end of the existing course list, as well as handling the response. How you shape the state is completely up to you and it can be re-jigged accordingly.
In order for this code to work, you will need to add support for the spread operator. If you are using babel it can be done like this. Creating a new object is important to ensure that you don't mutate the existing state. It will also mean react-redux knows the state has changed. Spread operator isn't essential and this can be done with Object.assign, but that syntax is ugly IMO.
I would like to add a loading animation to my website since it's loading quite a bit when entering the website. It is built in ReactJS & NodeJS, so I need to know specifically with ReactJS how to add a loading animation when initially entering the site and also when there is any loading time when rendering a new component.
So is there a way to let people on my website already, although it's not fully loaded, so I can add a loading page with some CSS3 animation as a loading screen.
The question is not really how to make a loading animation. It's more about how to integrate it into ReactJS.
Thank you very much.
Since ReactJS virtual DOM is pretty fast, I assume the biggest load time is due to asynchronous calls. You might be running async code in one of the React lifecycle event (e.g. componentWillMount).
Your application looks empty in the time that it takes for the HTTP call. To create a loader you need to keep the state of your async code.
Example without using Redux
We will have three different states in our app:
REQUEST: while the data is requested but has not loaded yet.
SUCCESS: The data returned successfully. No error occurred.
FAILURE: The async code failed with an error.
While we are in the request state we need to render the spinner. Once the data is back from the server, we change the state of the app to SUCCESS which trigger the component re-render, in which we render the listings.
import React from 'react'
import axios from 'axios'
const REQUEST = 'REQUEST'
const SUCCESS = 'SUCCESS'
const FAILURE = 'FAILURE'
export default class Listings extends React.Component {
constructor(props) {
super(props)
this.state = {status: REQUEST, listings: []}
}
componentDidMount() {
axios.get('/api/listing/12345')
.then(function (response) {
this.setState({listing: response.payload, status: SUCCESS})
})
.catch(function (error) {
this.setState({listing: [], status: FAILURE})
})
}
renderSpinner() {
return ('Loading...')
}
renderListing(listing, idx) {
return (
<div key={idx}>
{listing.name}
</div>
)
}
renderListings() {
return this.state.listing.map(this.renderListing)
}
render() {
return this.state.status == REQUEST ? this.renderSpinner() : this.renderListings()
}
}
Example using Redux
You can pretty much do the similar thing using Redux and Thunk middleware.
Thunk middleware allows us to send actions that are functions. Therefore, it allows us to run an async code. Here we are doing the same thing that we did in the previous example: we keep track of the state of asynchronous code.
export default function promiseMiddleware() {
return (next) => (action) => {
const {promise, type, ...rest} = action
if (!promise) return next(action)
const REQUEST = type + '_REQUEST'
const SUCCESS = type + '_SUCCESS'
const FAILURE = type + '_FAILURE'
next({...rest, type: REQUEST})
return promise
.then(result => {
next({...rest, result, type: SUCCESS})
return true
})
.catch(error => {
if (DEBUG) {
console.error(error)
console.log(error.stack)
}
next({...rest, error, type: FAILURE})
return false
})
}
}