Uncaught TypeError: Cannot read property 'modules' of undefined

[dzintars]

When calling selector before actual data are arrived o get this error.

Uncaught TypeError: Cannot read property 'modules' of undefined
    at selectors.ts:33
    at index.js:70
    at index.js:30
    at index.js:84
    at index.js:30
    at index.js:80
    at Object.selectModulesByApplicationId (index.js:30)
    at HTMLElement.mapState (component.ts:12)
    at HTMLElement.<anonymous> (index.ts:94)
    at HTMLElement.<anonymous> (index.ts:85)

If i debug the selectors i can see that at first render slices are empty. There are no applications and modules, but from the component i am calling ModuleSelectors.selectModulesByApplicationId(state, { applicationId: this.appid }) and so there is no data match for the requested appid. After data arrives, reducer updates the state and component gets re-rendered, so from UI perspective user sees the data, but in console there is this error.

My assumption is that i should handle isFetching state for the components and call the selector only when fetching is done.

[dzintars]

This proves that data is not yet there at first render:

mapState(state: RootState) {
    return {
      pathname: RoutingSelectors.pathname(state),
      isApplicationsFetching: ApplicationSelectors.selectFetchState(state),
      isModulesFetching: ModuleSelectors.selectFetchState(state),
      modules:
        this.isApplicationsFetching && this.isModulesFetching
          ? ``
          : ModuleSelectors.selectModulesByApplicationId(state, { applicationId: this.appid }),
    }
  }

Probably need some HOC which monitors the data...?

[dzintars]

OOOrrrr.... passing that argument is BAD... ideally, this.appid should be represented in store like selectedApplicationId: '' and it should have it's own selector.
https://github.com/reduxjs/reselect#q-how-do-i-create-a-selector-that-takes-an-argument