Adding Properties To Created Redux Store In Typescript

I'm having issues adding a property when I create a new Redux Store in Typescript: const bindMiddleware = middleware => { if (process.env.NODE_ENV !== 'production') { cons

Solution 1:

@types/
| - redux.d.ts
src/
| ...
| ... store.ts

in redux.d.ts

import * as Redux from "redux"

declare module "redux" {
  export interface Store {
    sagaTask: ... // provide the types for `store.sagaTask` here 
  }
}

in store.ts

const store = createStore(...)
store.sagaTask = ...

this is known as declaration merging / module augmentation.

You need to also setup your tsconfig.json to read types from this @types dir. Add "typeRoots": [ "./@types", "./node_modules/@types" ] to this file (note: these are relative to your baseDir, so modify accordingly.

Also note that you're creating a contract between your types and the code you write. If you fail to setup your middleware properly, sagaTask will be Required in types but undefined in reality.

Solution 2:

I haven't used Saga so I'm not sure about best practices or what ramifications this approach might have, but the issue is that the Store type doesn't have a sagaTask, so TypeScript won't let this happen. The easiest way that I can see to solve this is to extend Store and add a sagaTask field, then copy the old store to a new object of the extended type.

The downside to this is that you could easily run into a situation where a function is expecting an object with a Store type, so it won't accept this new object.

Are you sure this needs to be a property of the store, or can you just run sagaMiddleware.run(rootSaga)?