Reducer: getting information about value changes at the store - reactjs

Question

I don't understand how to get an updated value from the reducer store. For example, I have a React component. In this component after some actions, for example, after a few clicks on a button, I call the action from my reducer actions script like this.props.PostSomethingToServer(). Then the action sends some data to the node express server. The server makes some changes with data and then sends a response to the client store reducer. How can I get the updated data from the reducer store? I need to call another function in this React component with updated values.
By the way, I use mapStateToProps and export default connect() in the React component. As I know, mapStateToProps and export default connect() help to get data from the store before render(). But I still don't understand how to get updated data from the store after some actions.
A couple of code:
React component:
ChangeArrayData(){
let something = [];
// filling this array and modifying values
//then I call the action
this.props.postSomethingToServer(something);//something will be changed by server logic and will be returned with updated data by a response.
//then I wanna export the data to .excel, for example
this.ExportToExcel(); // here I have to get updated data from the reducer, but I don't have any information about changes in the reducer.
}
Reducer action:
export const postSomethingToServer= rankedElements => dispatch => {
axios
.post("/api/postData", elements)
.then(response => {
dispatch({
type: POST_SOMETHING_SUCCESSFUL,
status : "success",
payload: response.data
});
//... etc.
Reducer:
const initialState = {
something: {},
status: "",
error : ""
};
export default function(state = initialState, action) {
switch (action.type) {
case POST_SOMETHING:
return {
...state,
status: action.status,
}
case POST_SOMETHING_SUCCESSFUL:
return {
...state,
status: action.status,
something: action.payload
}
case GET_ERRORS:
return {
...state,
status: action.status,
error: action.error
}
default:
return state;
}
}

Answer 1

You Should assign reducer state values to some local state like following:
`const mapStateToProps = state => ({
contacts: state.data
});
export default connect(mapStateToProps, { actions })
(withStyles(contactStyle)(Contact));`
Here 'contacts' is a local state name we are using in the class and 'data' is a state name that we return from reducer after updating a state.
You can access the updated data using componentWillReceiveProps method like,
`componentWillReceiveProps(nextProps) {
if(nextProps.contacts !== undefined) {
//Handle updated states here
}
}`

Answer 2

After you dispatch the action, your reducer state something should have the data you expect. Given that you have mapped the data in your mapStateToProps function you can access it via props.
ChangeArrayData() {
let something = [];
this.props.postSomethingToServer(something);
this.ExportToExcel();
console.log(this.props.somethingReducerState);
}
const mapStateToProps = (state) => ({
somethingReducerState: state.yourReducerName.something,
});

Answer 3

I have the solution: I'm using componentWillReceiveProps(nextProps) and can receive a result from the reducer.
Thanks all for the answers.