How to access state inside Redux reducer?

I would use thunk for this, here’s an example:

export function updateProduct(product) {
  return (dispatch, getState) => {
    const { accountDetails } = getState();

    dispatch({
      type: UPDATE_PRODUCT,
      stateOfResidenceId: accountDetails.stateOfResidenceId,
      product,
    });
  };
}

Basically you get all the data you need on the action, then you can send that data to your reducer.