Accept initialState function to allow dynamic initial state in AoT

[bfricka]

This is problem carried over from @ngrx/store (see: 273, 348).

AoT requires static objects in module definitions, so dynamic initial state is only possible with:

1. At least support for an initialState function
   or
2. Putting a meta-reducer on top of everything for this purpose alone (as described in my comment on 348). The second case seems unnecessarily unnecessarily complicated for something so easy to support in the library itself.

[robwormald]

Seems legit. Want to take a crack at making a PR?

[brandonroberts]

You can also provide your own initial state through the INITIAL_STATE token.

import { INITIAL_STATE } from '@ngrx/store';

// in the providers array
{ provide: INITIAL_STATE, useFactory: getInitialState }

[bfricka]

@brandonroberts That's a great idea, and I'm a bit embarrassed I didn't think to do it.

That said, allowing initialStateFactory to take a function is really trivial, and considering it's necessary for AoT, it might be worthwhile to add support for it.

I'm happy to open a PR, but I'm wondering your thoughts. Either a PR documenting how to override the provider (since you're exporting all the tokens), or a PR allowing initialState to be a function.

Thanks

[brandonroberts]

@bfricka a PR allowing initialState to be a function along with documentation would be good.

[bfricka]

@brandonroberts @robwormald This PR should be ready to. It looks like there's perhaps an issue with the COVERALLS_REPO_TOKEN environment variable not being set in CircleCI. You can add it to the circle project without committing it to git (Project settings > Environment Variables).

[maxisam]

@bfricka Could you explain how to use initialStateFactory to dynamically get the initial state from the backend?