Thursday, July 27, 2017

NGRX Platform, redux

I have been using something similar undoables for an undo/redo function in my reducers. This implementation maintains the last array in memory, which would consume quite a few resources, so I rewrote it to keep the changed documents available for redo, and implemented effects to update the persistent storage. Worked fine in ngrx/store v2. And in ngrx/store v4 if I didn't use AOT. The feared ErrorError encountered resolving symbol values statically.

In my reducer definition I had code that looked like this:

export const reducers: ActionReducerMap = {
    connection: fromConnections.reducer,
    contactlist: undoable(fromContactList.reducer),
    contactemails: undoable(fromContactEmail.reducer),
    contactphones: undoable(fromContactPhone.reducer),
    contactwebsite: undoable(fromContactWebsite.reducer),
};

undoable gets a reducer as a parameter and returns it. AOT doesn't like it.

So there are two solutions.

You can provide the reducers.

export const REDUCER_TOKEN = new InjectionToken>('Registered Reducers');

export const reducerProvider = [
    { provide: REDUCER_TOKEN, useValue: reducers },
];

creates a token and provider, then in your module some magic.

// WORKAROUND HERE
Object.assign(REDUCER_TOKEN, reducers);
// WORKAROUND HERE

Then import the StoreModule

imports: [
        BrowserModule,
        CommonModule,
      ...
        StoreModule.forRoot(REDUCER_TOKEN),
],
providers: [
        reducerProvider,
]

The Object.assign hack is necessary, it won't work without it, at least in v 4.0.1.

The second way is to

export function undoableLayoutReducer(state: any, action: Action): fromLayout.State {
    return undoable(fromLayout.reducer)(state, action);
}

export const reducers: ActionReducerMap = {
    layout: undoableLayoutReducer,
};

which encapsulates the factory function in something that AOT likes. Right now this is required if you have a factory for your reducer in a feature store, as the forFeature doesn't as yet work with providers.




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