Typescript + Redux + Typescript Readonly Interfaces

second-iteration.ts

import { TypedRecord, recordify } from "typed-immutable-record";
// scaffolding
interface IPostState {
  post: IPost | null;
  isLoading: boolean;
}
interface IPostStateRecordPart {
  post: IPostRecord; // this interface is created in a similar fashion.
  isLoading: boolean;
}
interface IPostStateRecord
  extends TypedRecord<IPostStateRecordPart>,
    IPostStateRecord {}
function recordifyPostState(plainState: IPostState): IPostStateRecord {
  return recordify<IPostStateRecordPart, IPostStateRecord>({
    post: plainState.post
      ? recordify<IPostRecordPart, IPostRecord>(plainState.post)
      : null,
    isLoading: plainState.isLoading,
  });
}
// reducers
const INITIAL_STATE: IPostStateRecord = recordifyPostState({
  post: null,
  isLoading: false,
});
function postReducer(
  state: IPostStateRecord = INITIAL_STATE,
  action,
): IPostStateRecord {
  switch (action.type) {
    case "FETCHED": {
      return state.withMutations(currentState =>
        currentState.set("post", action.payload.post).set("isLoading", false),
      );
    }
    case "UPDATED_TITLE": {
      return state.setIn(["post", "title"], action.payload.title);
    }
    default: {
      return state;
    }
  }
}