React-Redux TypeScript错误

Question

Tryign to implement TypeScript with React/Redux and I'm running into some issues with my Types.

I have these types:

export interface IAuthState {
  isSignedIn: Boolean | null;
  userId: string | null;
}

export interface IStream {
  id: string;
  title: string;
  description: string;
  userId: string;
}

export interface IStreamState {
  streams: { [index: string]: IStream };
}

Then I have two components:

interface IStreamsProps {
  fetchStreams: () => void;
  streams: IStreamState;
  currentUserId: String | null;
  isSignedIn: Boolean | null;
  auth: IAuthState;
}

class StreamsList extends Component<IStreamsProps, IAppState> {
   // Error: The Property Map does not exist on type IStreamState
   renderList() {
       return this.props.streams.map((stream: IStream) => (// CODE)
   }
}


const mapStateToProps = (state: IAppState) => {
  return {
    streams: Object.values(state.streams),
    currentUserId: state.auth.userId,
    isSignedIn: state.auth.isSignedIn
  };
};

export default connect(
  mapStateToProps,
  { fetchStreams }
)(StreamsList);

Then I have another similar component:

const mapStateToProps = (state: IAppState, ownProps: HomeProps) => {
  return {
    //Error: Element implicitly has an 'any' type because expression of type 'any' can't be used to index type 'IStreamState'
    stream: state.streams[ownProps.match.params.id]
  };
};

export default connect(
  mapStateToProps,
  null
)(StreamEdit);

How do I solve these two errors:

Error 1: The Property Map does not exist on type IStreamState

Error 2: Element implicitly has an 'any' type because expression of type 'any' can't be used to index type 'IStreamState'

Answer 1

You incorrectly defined IStreamState . Look closely. You've defined it as an object

export interface IStreamState {
  streams: { [index: string]: IStream }[];
}
// equivalent declaration using type:
export type IStreamState = { 
  streams: { [index: string]: IStream }[]
}

I'm sure you mean to type it as just an array, as so:

export type IStreamState = { [index: string]: IStream }[]

EDIT: While not directly related to your question, you need to be careful with your types. I noticed you used IAppState in two different places. The class declarations are for props and local state. IAppState appears to be for your redux store.

// the second generic argument is for `this.state`
class StreamsList extends Component<IStreamsProps, IAppState> {

EDIT2: Defining both arguments in a class is optional. If you leave the second one out, it defaults to {} for you.

It's impossible to be 100% sure as to why you're having that issue in your mapStateToProps , because I don't know what IAppState looks like. Just go double back and confirm your typing for state.streams is exactly what you expect.