javascript - react-redux with thunk - getState is not a function -

i'm receiving error typeerror: getstate not function i'm attempting similar example @ http://redux.js.org/docs/advanced/asyncactions.html

action.js - error occurs here

export const fetchcategoriesifneeded = (dispatch, getstate) => {     if(shouldfetchcategories(getstate())){         return dispatch(fetchcategories())     } } 

app.js

  componentdidmount(){     this.props.dispatch(fetchcategoriesifneeded())   } 

...

const mapstatetoprops = (state, props) => {   return {     isfetching: state.isfetching,     categories: state.categories     } } 

reducer.js

function data (state = initialstate, action){     switch(action.type){         case receive_categories:             return {                 ...state,                 isfetching: false,                 categories: action.categories             }         case request_categories:             return {                 ...state,                 isfetching: true             }         default:             return state     }     return state } 

omitted of code readability.

i've tried , receive typeerror: dispatch not function

export function fetchcategoriesifneeded(){     return(dispatch, getstate) =>{         var state = getstate()         if(shouldfetchcategories(state)){             dispatch(fetchcategories())         }     } } 

wiki