How to correctly use 'connect' in react-redux with Typescript

Question

I'm using typescript in an application, but found some problem with react-redux. The 'connect' method reports a problem and I have no idea with it since I'm a rookie with typescript and redux. What should I do or where in my code should be modified? Thanks a lot

Application built with [email protected], [email protected], [email protected].

// article
interface IArticle {
  title: string,
  author: string
}

// state
interface MyState {
  list: [],
  article: IArticle
}

// stateMapToProps
interface MyStateProps {
  article: IArticle
}

// router match
interface MatchParams {
  id: string
}

// own props
interface MyOwnProps extends RouteComponentProps < MatchParams > {
  article: IArticle,
  dispatch: (o: object) => {}
}

class ArticleContainer extends Component < MyOwnProps, {} > {
  constructor(props: MyOwnProps) {
    super(props);
  }

  componentDidMount() {
    const {
      dispatch
    } = this.props;
    const id = this.props.match.params.id
    dispatch(fetchArticle(id))
  }

  render() {
    const {
      article
    } = this.props;
    return ( <
      Article article = {
        article
      } > < /Article>
    )
  }
}

const mapStateToProps = (state: MyState): MyStateProps => {
  return {
    article: state.article
  }
}

export default connect < MyStateProps, {}, {
  article: IArticle
} > (
  mapStateToProps
)(ArticleContainer)

Here is the code of async action fetchArticle

function fetchArticle(id: string) {
  return function(dispatch: (action: AnyAction) => {}): Promise<void> {
    dispatch(getArticle(id))

    return axios.get(`/article/${id}`)
      .then(res => {
        dispatch(getArticleSuccess(res.data))
      })
  }
}

Error happens at the export line and message is as below:

Argument of type '(state: MyState) => MyStateProps' is not assignable to parameter of type 'MapStateToPropsParam'. Type '(state: MyState) => MyStateProps' is not assignable to type 'MapStateToPropsFactory'. Types of parameters 'state' and 'initialState' are incompatible. Type '{}' is missing the following properties from type 'MyState': list, articlets(2345)

Just remove the typing from connect. Connect is already infers typing, from mapStateToProps. export default connect(mapStateToProps)(ArticleContainer); — eenagy
also, your component should be Component<MyOwnProps, MyState> — eenagy
@eenagy thanks first. I tried and instead the ArticleContainer part in export line report a message, also the interface MyState represents the structure of the store created with redux, not the 'state' of the Class, so I think there is no need to put it in the generics. I hope I make myself understandable. — smilebuz
And the error message for ArticleContainer in connect part is as below(only record the first sentence since it is too long to write here): Argument of type 'typeof ArticleContainer' is not assignable to parameter of type 'ComponentType<Matching<MyStateProps & DispatchProp<AnyAction>, MyOwnProps>>'......ts(2345) — smilebuz

Fyodor Fyodor · Accepted Answer · 2019-07-10T06:45:55

Minimum steps to be able to compile your code:

MyOwnProps should be

import { AnyAction } from 'redux';

interface AppThunkAction<TAction> {
    (dispatch: (action: TAction) => void, getState: () => MyState): any;
}

// As you're going to dispatch thunk actions, dispatch should be overloaded
interface Dispatch<TAction> {
    (action: AppThunkAction<TAction>): any
    (action: TAction): TAction
}

// own props
interface MyOwnProps extends RouteComponentProps<MatchParams> {
    article: IArticle,
    dispatch: Dispatch<AnyAction>
}

If you want to provide types for connect function, add MyState as last type like so

export default connect <MyStateProps, {}, {
        article: IArticle
    }, MyState >(
        mapStateToProps
)(ArticleContainer)

Or you can allow compiler to infer types itself, which is preferred

export default connect(
    mapStateToProps
)(ArticleContainer)

So working result

import { Component } from 'react';
import { RouteComponentProps } from 'react-router-dom';
import { connect, ResolveThunks } from 'react-redux';
import { AnyAction } from 'redux';
import axios from 'axios';

// article
interface IArticle {
    title: string,
    author: string
}

// state
interface MyState {
    list: [],
    article: IArticle
}

// stateMapToProps
interface MyStateProps {
    article: IArticle
}

// router match
interface MatchParams {
    id: string
}

export interface AppThunkAction<TAction> {
    (dispatch: (action: TAction) => void, getState: () => MyState): any;
}

interface Dispatch<TAction> {
    (action: AppThunkAction<TAction>): any
    (action: TAction): TAction
}

// own props
interface MyOwnProps extends RouteComponentProps<MatchParams> {
    article: IArticle,
    dispatch: Dispatch<AnyAction>
}

function getArticle(id: string) {
    return {
        type: 'GET_ARTICLE',
        id
    }
}

function getArticleSuccess(i: any) {
    return {
        type: 'SET_ARTICLE',
        i
    }
}



const fetchArticle = (id: string): AppThunkAction<AnyAction> =>
    (dispatch, getState) => {
        dispatch(getArticle(id))

        return axios.get(`/article/${id}`)
            .then(res => {
                dispatch(getArticleSuccess(res.data))
            })
    }

class ArticleContainer extends Component<MyOwnProps, {}> {
    constructor(props: MyOwnProps) {
        super(props);
    }

    componentDidMount() {
        const {
            dispatch
        } = this.props;
        const id = this.props.match.params.id
        dispatch(fetchArticle(id))
    }

    render() {
        const {
            article
        } = this.props;
        return (<div>article: {article}</div>
          )
        }
      }

const mapStateToProps = (state: MyState): MyStateProps => {
  return {
                article: state.article
          }
        }

export default connect(
            mapStateToProps
)(ArticleContainer)

How to correctly use 'connect' in react-redux with Typescript

3 Answers