for example, write code like this in a class component, state= {currentPic:this.props.pic}; pic is data passed in through connect (mapStateToProps), why is the value of each property of props in the constructor undefined? The function below the constructor uses this.props.xx but can access the value
you passed the redux, you write the values in the reducer as fixed to see if you can get it, just check up a little bit
No props? Normally, you can get it
constructor(props) {
super(props);
this.state = {
popover: false,
Data:2,
displayQrCode: false,
imgBase64: '',
};
}state because constructor is the first part of the component to execute. If the value of the property of state is this.props.xx, then it will be undefined (https://codeshelper.com/q/10...)
.react projects cannot save store? using redux, data index.js ReactDOM.render( <Provider store={store}> <Router > < Provider>, document.getElementById( root )) registerServiceWorker() actions export const SET_USER = ...
currently only know the traditional usage const App = connect( mapStateToProps, mapDispatchToProps )(Counter); but many projects use @connect(state => ({ value: state.global.value, extinfo: state.extinfo, })) I can understand what i...
As a matter of fact, there are several questions, which have been stuck for a long time. I don t know why 1. If the state of both reducer has a value, store.subscribe (() = > { console.log("================store:"+JSON.stringify(store)); });...
The function applyMiddleware (.middlewares) in applyMiddleware.js is used to generate the middleware chain that action passes through according to the middleware. Let s first take a look at the implementation of an incorrect version: export default fu...
normal routing page gets redux: container.js react-redux redux-thunk export default withRouter(connect(mapStateToProps, mapDispatchToProps)(couter)); route.js const AppRouter = () => ( <HashRouter> <UI > { ...
problem description error message: Store does not have a valid reducer. Make sure the argument passed to combineReducers is an object whose values are reducers. the environmental background of the problems and what methods you have tried I put re...
let patentListDefault={ list:[], count:0, isLoading: false, } export const patentDatas = (state=patentListDefault, action = {}) => { let imuDataList; let imuItem; switch(action.type){ case SAVEPATENTLIST : ...
import const store = applyMiddleware(ReduxThunk)(createStore)(reducers); const App = connect( state => (state), dispatch => ({ action: bindActionCreators(actions, dispatch) }) )(Component); const mountPoint = document.creat...
use redux case BEGIN_TO_LOGIN : { let cartState = { ...state, userInformation: [...state.userInformation, action.payload] } beginner redux, if the new state is the same as the existing state, ...
I want to add a mapDispatchToPropsReview, to this component, but I can t get it in props . main file import React from react ; import Review from . components Review ; import . assets styles index.less ; import rootReducer from .. .. .. ...
it is very common for an interview question. Although a large number of theoretical answers are found in the evening, I want to know how to separate the front and rear ends in practical projects . the concept of ssr server rendering has always been vag...
this is the Table component {this.props.tableData.map((item, index) => { return ( <tr key={index}> <td>{item.id}< td> <td>{item.name}< td> <td>{item.price}< td> <td...
Global state and reusable state are not mentioned for the time being. adding a page will have three pop-up windows, each of which has been extracted into a separate component. whether the status of these pop-up windows needs to be stored in redux. T...
problem description ` in the process of server rendering, cross-domain is always unsuccessful, and the address of each request for data will go to ` under localhost:3000. the environmental background of the problems and what methods you have tried ...
in ant design, we usually put the form component export default MHeader = Form.create({})(MHeader); then let {getFieldProps} = this.props.form; const { getFieldDecorator } = this.props.form; but we redux also need to wrap components in connect, and ...
The default red area in the figure is rendered according to the array hostedLand , with an initial length of 1. hostedLandlength2 statehostedLandlength and the console does not output anything. reducer: import { addHostedLand } from .. actions ...
I only want to use redux-devtools-extension and redux-logger in the development environment, so I created two store , and then made a judgment, but after packaging, I found that this judgment did not work, redux-devtools-extension can always be l...
I only want to use redux-devtools-extension and redux-logger in the development environment, so I created two store , and then made a judgment, but after packaging, I found that this judgment did not work, redux-devtools-extension can always be l...
the figure is as follows: how do components get values in store dynamically, just like this.$store.state in vue? index.js import React from react ; import ReactDOM from react-dom ; import App from . App ; import { BrowserRouter } from r...
the selectDerivedProps function in the react-redux source code connectAdvanced.js will determine whether store and selectorFactoryOptions have changed. In addition to the first execution here, when else will you change these two values? ...