mapDispatchToProps takes the dispatch function as a parameter and then returns that function with the property of the addMessage action creator

Map dispatch to props

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

// change code below this line
const mapDispatchToProps = dispatch => {
  return {
    submitNewMessage: function(message) {
      dispatch(addMessage(message));
    }
  }
}