React and Redux - Connect Redux to the Messages App

[NV2017]

Tell us what’s happening:

Describe your issue in detail here.

1. Problem is solved as intended.
2. But I got this interesting observation from this which seasoned developers can perhaps explain:

In the AppWrapper component from lines 90 to 102, there’s a constructor object/part of code from lines 91 to 93.

Removing lines 91 to 93 (constructor for AppWrapper) still makes the code/program work as intended; and this exercise is also accepting this solution, no objections.

Lines 91 to 93 (constructor for AppWrapper) are clearly not for this demo smallish program; so, & here’s the interesting question, when is this ‘constructor for AppWrapper’ part needed?

Thanks!

Your code so far

// Redux:
const ADD = 'ADD';

const addMessage = (message) => {
  return {
    type: ADD,
    message: message
  }
};

const messageReducer = (state = [], action) => {
  switch (action.type) {
    case ADD:
      return [
        ...state,
        action.message,action.message
      ];
    default:
      return state;
  }
};

const store = Redux.createStore(messageReducer);

// React:
class Presentational extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      input: '',
      messages: []
    }
    this.handleChange = this.handleChange.bind(this);
    this.submitMessage = this.submitMessage.bind(this);
  }
  handleChange(event) {
    this.setState({
      input: event.target.value
    });
  }
  submitMessage() {
    this.setState((state) => {
      const currentMessage = state.input;
      return {
        input: '',
        messages: state.messages.concat(currentMessage)
      };
    });
  }
  render() {
    return (
      <div>
        <h2>Type in a new Message:</h2>
        <input
          value={this.state.input}
          onChange={this.handleChange}/><br/>
        <button onClick={this.submitMessage}>Submit</button>
        <ul>
          {this.state.messages.map( (message, idx) => {
              return (
                 <li key={idx}>{message}</li>
              )
            })
          }
        </ul>
      </div>
    );
  }
};

// React-Redux:
const mapStateToProps = (state) => {
  return { messages: state }
};

const mapDispatchToProps = (dispatch) => {
  return {
    submitNewMessage: (newMessage) => {
       dispatch(addMessage(newMessage))
    }
  }
};

const Provider = ReactRedux.Provider;
const connect = ReactRedux.connect;

// Define the Container component here:
const Container = connect(mapStateToProps,mapDispatchToProps)(Presentational);

class AppWrapper extends React.Component {
  constructor(props) {
    super(props);
  }
  render() {
    // Complete the return statement:
    return (
      <Provider store={store}>
        <Container />
      </Provider>
    );
  }
};

Your browser information:

User Agent is: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36

Challenge Information:

React and Redux - Connect Redux to the Messages App

freeCodeCamp.org