Edited. People have suggested passing in values to my action creator but I've tried that every way I can think of and it fails to work.
I'm currently getting my first taste of Redux and trying to get my call to mapDispatchToProps to read information in a form on button click but I'm not clear as how to get it to do so. The form component is rendered by React, and so it's a question of being able to bind when it's available but Redux is a monkey wrench I don't know how to compensate for yet. Essentially I have this for my component:
import React from 'react';
import { connect } from 'react-redux';
import { action } from '../actions/actionFile';
const Add = (props) => (
<div className="add">
<input className="field-one" type="text" placeholder="One" />
<input className="field-two" type="number" placeholder="Two" />
<input className="field-three" type="number" placeholder="Three" />
<button onClick={() => props.addItem('Literally anything')}>+</button>
</div>
)
const mapDispatchToProps = (dispatch) => {
return {
action: () => dispatch(action({
// I have three fields I need to update in the store.
}))
}
}
export default connect(null, mapDispatchToProps)(Add);
And this for my actions file:
import { ADD_ITEM } from '../constants/items';
export const addItem = (val) => {
return {
type: ADD_ITEM,
val
}
}
But if I run this and set a breakpoint inside the action creator the val value is undefined. For some reason Redux isn't letting me feed dynamic data to the action creator and I don't understand why.
Obviously I can't just pull the information with querySelector because the form doesn't exist when the callback is loaded. If I fill the object passed to the action with hard-coded dummy values it works, but I'm not able to pull in data from the form fields. I'm not even clear as to where to start with this. Any direction is greatly appreciated.
You can't access any data from Redux state, or from inside the component, in mapDispatch, because it is used as part of a wrapper component that goes around your actual component (and thus doesn't have access to anything in your component's state).
Your main options are:
Pass any necessary values as arguments into the function, like props.action(a, b, c)
Switch to using the React-Redux hooks API (useSelector and useDispatch), which lets you access data from the Redux store inside of your function component. You can then capture these values while defining a click handler.
Also, as a side note: if you are going to use connect, you should use the "object shorthand" form of mapDispatch rather than defining it as a function.
You just need to add onChange event handler to your three fields and store data of each input into your component state.
Then on button click dispatch action using this.props.action with data in your state.
In this way you can get all of your data into redux.
render() {
return <button onClick={() =>this.props.toggleTodo(this.props.todoId)} />
}
const mapDispatchToProps = dispatch => {
return { toggleTodo: todoId =>dispatch(toggleTodo(todoId)) }
}
For reference -Connect: Dispatching Actions with mapDispatchToProps ยท React Redux
Related
I know that you can do navigation.navigate("address", {/* params go here */ to send parameters over to another screen. But then you have to navigate there. Is there a way of sending params over without navigating?
I have a application with multiple screens. And I want to update a useState from another component by updating its params so that a button appears. But I dont want to navigate there, I just want to update it so when the user does go there the button will be there.
Like this:
const currentComponent = (navigation) {
return (
<Button onPress={navigation.updateParams("otherComponent", {shouldShowValue: true})} />
)
}
const otherComponent = (route, navigation) {
const {shouldShowValue} = route.params
const [shouldShow, setShouldShow] = useState(shouldShowValue);
return (
{shouldShow ? <Button> Yayy this button appears now <Button /> : null}
)
}
}
'''
this is just pseudo code and not at all
like the code I have written,
but its just meant as an example to get a
understanding of what I mean.
(updateParams) isnt a function that exists,
but I want something similiar like it.
Is there a way of updating the params in a
component from another component without having
to navigate there? Like with
navigate.navigate("address" {params go here})
but without the navigation part?
You can consider using useContext() hook to execute your functionality.
Using navigation library to pass param without navigating to that page is somehow misusing the navigation function.
With useContext, you can share the state(s) among components. If you want to change the value upon clicking action, you can also pass the useState hook into useContext. Alternatively, you can consider to use redux library to share state.
import { useState, createContext, useContext } from 'react';
const shareContext = createContext(null);
export default function demoUseContext() {
const [isClicked, setClicked] = useState(false);
return (
<shareContext.Provider value={{isClicked, setClicked}}>
<ComponentA />
<ComponentB />
</shareContext.Provider>
)
}
function ComponentA() {
const sharedParam = useContext(shareContext);
return (
<button onClick={() => sharedParam.setClicked(!sharedParam.isClicked)}>
click to change value
</button>
);
}
function ComponentB() {
const sharedParam = useContext(shareContext);
return (
sharedParam.isClicked && <div>it is clicked</div>
)
}
As the example above, the code pass the useState hook from parent component into context, where A is consuming the useState from context to setup isClicked via setClicked, B is consuming the value isClicked from context.
You can also manage to setup context with value not only in a hook, but a param / object / function as a callback.
For more details, please refer to https://reactjs.org/docs/hooks-reference.html#usecontext
There're multiple hooks including useContext fyi
Passing parameters to routes
There are two pieces to this:
Pass params to a route by putting them in an object as a second parameter to the navigation.navigate function: navigation.navigate('RouteName', { /* params go here */ })
Read the params in your screen component: route.params.
We recommend that the params you pass are JSON-serializable. That way, you'll be able to use state persistence and your screen components will have the right contract for implementing deep linking.
Background
So I have a simple example, a Form component (Parent) and multiple Input components (Children). Each individual Input component will have an useState hook to initialize and manage its value's state.
Issue
As with most forms, I would like to submit all of the data to a backend for processing. However, the issue is that I cannot retrieve the state of value from each Child Input component.
// app.jsx
import Form from "./Form";
export default function App() {
return <Form />;
}
// Form.jsx
import React from "react";
import Input from "./Input";
const handleSubmit = (e) => {
e.preventDefault();
console.log("Wait, how do I retreive values from Children Inputs?");
};
const Form = () => {
console.log("Form render");
return (
<form onSubmit={handleSubmit}>
Sample Form
<Input initial="username" name="user" />
<Input initial="email" name="email" />
<button type="submit">Submit</button>
</form>
);
};
export default Form;
// Input.jsx
import React from "react";
import useInputValue from "./useInputValue";
const Input = ({ name, initial }) => {
const inputState = useInputValue(initial);
console.log(`${name}'s value: ${inputState.value}`);
return <input {...inputState} />;
};
export default Input;
Plausible Solution
Of course, I can lift the Input states up to the Form component, perhaps in an obj name values. However, if I do that, every time I change the Inputs, the Form will re-render, along with all of the Inputs.
To me, that is an undesirable side-effect. As my Form component gets bigger, this will be more costly to re-render all inputs (inside the form) every time one input changes.
Because of that, I would like to stick with my decision of having each individual input manage its own state, that way if one input changes, not all other input will re-render along with the Parent component.
Question
If each of the Child components manages its own state, could the Parent component access the value of that state and do actions (like form submission)?
Update
Many answers and comments mentioned that this is premature optimization and the root of all known evil; which I agree with, but to clarify, I am asking this question with a simple example because I wanted to find a viable solution to my current and more complex project. My web app has a huge form (where all states are lifted to the form level), which is getting re-rendered at every change in its inputs. Which seemed unnecessary, since only one input is changed at a time.
Update #2
Here is a codesandbox example of the issue I am having. There are two forms, one with all states managed by individual Child input components, and the other has all states lifted up in the form level. Try entering some values and check the console for log messages. One can see that with all states lifted to the form level, every change will cause both inputs to be re-rendered.
I think yes, you can share state. Also there are 3 options:
I recommend you to use such library as Formik. It will help you in your case.
You can share state using useState() hook as props.
Use such tools as Redux Toolkit (if we are speaking about memoisation), useContext() and etc.
If the thing you want is getting final values from input, assign ref to each input and access using emailRef.current.value in the submit function.
import { useState, useRef, forwardRef } from 'React';
const Input = forwardRef((props, ref) => {
const [value, setValue] = useState('');
return <input ref={ref} value={value} onChange={(e) => {setValue(e.target.value)}} {...props} />;
});
const App = () => {
const emailRef = useRef(null);
const submit = () => {
const emailString = emailRef.current.value
};
return (
<>
<Input ref={emailRef} />
<button onClick={submit}>Submit</button>
</>
);
};
If the parent needs to know about the childs state, you can
move the state up. This is resolved by passing down a setState function that the child calls (the states data is available in the parent)
use a context https://reactjs.org/docs/context.html
use a state management library e.g. redux
In your simple case I'd go with 1)
There is an event handler for click and when it triggered i want to pull specific data from redux using selector where all logic many-to-many is implemented. I need to pass id to it in order to receive its individual data. Based on rules of the react the hooks can be called in function that is neither a React function component nor a custom React Hook function.
So what is the way to solve my problem ?
const handleMediaItemClick = (media: any): void => {
// For example i check media type and use this selector to pull redux data by id
const data = useSelector(playlistWithMediaSelector(imedia.id));
};
As stated in the error message, you cannot call hooks inside functions. You call a hook inside a functional component and use that value inside the function. The useSelector hook updates the variable each time the state changes and renders that component.
Also, when you get data with useSelector, you should write the reducer name you need from the redux state.
const CustomComponent = () => {
// The data will be updated on each state change and the component will be rendered
const data = useSelector((state) => state.REDUCER_NAME);
const handleMediaItemClick = () => {
console.log(data);
};
}
You can check this page for more information.https://react-redux.js.org/api/hooks#useselector
You should probably use local state value to track that.
const Component = () => {
const [imediaId, setImediaId] = useState(null);
const data = useSelector(playlistWithMediaSelector(imediaId));
function handleMediaClick(id) {
setImediaId(id)
}
useEffect(() => {
// do something on data
}, [imediaId, data])
return <div>...</div>
}
Does that help?
EDIT: I gather that what you want to do is to be able to call the selector where you need. Something like (considering the code above) data(id) in handleMediaClick. I'd bet you gotta return a curried function from useSelector, rather than value. Then you would call it. Alas, I haven't figured out how to that, if it's at all possible and whether it's an acceptable pattern or not.
In my React codebase I've integrated Redux usign react-redux and I'm using the useDispatch hook to dispatch actions from my views. I just have one problem I don't have access to the updated values just after updating the store. Is there a way for me to wait for the state update to complete like await or something like a callback where I can execute the other code?
This is how my code looks like:
import React from 'react';
import { useDispatch } from "react-redux";
import { setCore } from "../store/global";
// the value from the store is drilled down as props
export default function Home({ instance, core }) {
const dispatch = useDispatch();
const onConnect = async () => {
// core may have some value before but I want to clear
console.log(core); // prints the old value
await dispatch(setCore(null));
console.log(core); // Need to have null here
}
return (
<div>
<button onClick={onConnect}>Connect</button>
</div>
);
}
Dispatching by default is 100% synchronous. There's no need to wait for the dispatch itself.
However, waiting for the component's props to update is a completely different question. Given that code, core will never update, because the definition of onConnect has already captured the value of core at the time the function was defined.
You may want to move that portion of the logic into a useEffect() hook that will trigger when the value of core has changed.
This is my component's class:
import React, { Component } from 'react';
import {connect} from 'react-redux';
import Button from '../UI/Button/Button';
import * as actions from '../../store/actions';
class Password extends Component {
submitPassword=(e)=>{
e.preventDefault();
this.props.submitPassword(this.state.password, this.props.levelNumber);
}
render() {
<Button clicked={this.submitPassword} >
Submit password
</Button>
}
}
const mapStateToProps = state => {
return {
};
}
const mapDispatchToProps = dispatch => {
return {
submitPassword: (password,levelNumber) => dispatch(actions.submitPassword(password,levelNumber))
};
}
export default connect(mapStateToProps, mapDispatchToProps)(Password);
and this is my action:
export const submitPassword = () => {
// HERE ALL MY LOGIC !!!
return {
level:undefined,
type:actions.PASSWORD
}
}
The code working all correctly including params and logic.
I wanna that every time that finish to execute the function submitPassword A third component refresh/reload with the new props. Attention! My third component is parent, not child!
It's possibile to send a command from action to component? How can I do it? I have already tried with:
componentWillReceiveProps() {
console.log("new props");
}
in my component but he can not take the event.
normally a structure my redux store as follows
{
entities: {},
ui: {},
domain:{}
}
so for example when you execute submitPassword you execute all the logic and depending on the result you can dispatch another action to update the ui or the domain part so the componentes that are connected respond to those changes.
The UI holds information about UI changes, like if you are submiting info display a progress bar or if it has to display a dialog.
The domain part holds information related to the whole webapp, like loggin info and notifications.
You don't need always to pass new props for redux state to be accessed.
As redux is having immutable state, you'll always be getting new updated state no matter the previous one. So this will enforce your component to update props to get latest state from redux. This is done by <Provider> wrapper attached on root level.
So hence your props will be having new values whenever redux state gets updated.
The lifecycle you are looking is static getderivedstatefromprops(). This lifecycle gets executed whenever props are changed/updated.
I made visual implementation on fly that can aid you the picture. Here Redux State means Redux Store