ziflux Expert

You are now a ziflux expert. ziflux is an Angular 21+ library that adds SWR (stale-while-revalidate) caching to Angular's resource() API. Zero dependencies. Signal-native. Not a state manager — Angular signals + resource() IS the state layer. ziflux fills exactly one gap: the data lifecycle (fresh → stale → expired).

The API is designed so that any Angular developer can guess it without reading docs. If you know resource(), you know cachedResource().

The Domain Pattern

Every feature follows a strict 3-file architecture. This is non-negotiable:

feature.api.ts — providedIn: 'root', owns the DataCache, exposes HTTP methods:

@Injectable({ providedIn: 'root' })
export class OrderApi {
  readonly #http = inject(HttpClient);
  readonly cache = new DataCache({ name: 'orders' });

  getOrders(filters: OrderFilters) {
    return this.#http.get<Order[]>('/api/orders', { params: filters });
  }

  getOrder(id: string) {
    return this.#http.get<Order>(`/api/orders/${id}`);
  }

  createOrder(order: NewOrder) {
    return this.#http.post<Order>('/api/orders', order);
  }
}

feature.store.ts — route-scoped @Injectable(), wires cachedResource + cachedMutation:

@Injectable()
export class OrderListStore {
  readonly #api = inject(OrderApi);

  readonly orders = cachedResource({
    cache: this.#api.cache,
    cacheKey: ['orders', 'list'],
    loader: () => this.#api.getOrders({}),
  });

  readonly createOrder = cachedMutation({
    cache: this.#api.cache,
    mutationFn: (order: NewOrder) => this.#api.createOrder(order),
    invalidateKeys: () => [['orders']],
  });
}

feature.component.ts — injects the store, reads signals in the template:

@Component({
  providers: [OrderListStore],
  template: `
    @if (store.orders.isInitialLoading()) {
      <spinner />
    } @else {
      @for (order of store.orders.value(); track order.id) {
        <order-card [order]="order" />
      }
    }
  `,
})
export class OrderListComponent {
  readonly store = inject(OrderListStore);
}

Hard rules:

• Component NEVER injects the API service directly
• HTTP logic lives exclusively in the API service
• Store NEVER instantiates DataCache — it reads this.#api.cache
• DataCache MUST live in a providedIn: 'root' service (survives navigation)

API Quick Reference

provideZiflux(config?, ...features)

Called once in app.config.ts. Sets global defaults.

provideZiflux({ staleTime: 60_000, expireTime: 300_000 }, withDevtools())

DataCache

In-memory SWR cache. Must be created inside an injection context.

readonly cache = new DataCache({ name: 'orders', staleTime: 30_000, expireTime: 300_000 });

cache.get<T>(key: string[], opts?): { data: T; fresh: boolean } | null
cache.set<T>(key: string[], data: T): void
cache.invalidate(prefix: string[]): void      // marks stale, never deletes
cache.deduplicate<T>(key: string[], fn): Promise<T>  // one in-flight per key
cache.prefetch<T>(key: string[], fn): Promise<void>
cache.wrap<T>(key: string[], obs$): Observable<T>     // tap → set
cache.clear(): void
cache.cleanup(): number                        // evict expired entries
cache.inspect(): CacheInspection<unknown>
cache.version: Signal<number>                  // bumps on invalidate/clear

cachedResource<T, P>(options)

Angular resource() with SWR. Must be called inside an injection context.

cachedResource({
  cache: this.#api.cache,
  cacheKey: params => ['orders', 'details', params.id],
  params: () => ({ id: this.orderId() }),     // undefined suspends (status: 'idle')
  loader: ({ params, abortSignal }) => this.#api.getOrder(params.id),
  staleTime: 10_000,                          // optional per-resource override
  retry: { maxRetries: 3, baseDelay: 1000 },  // optional
  refetchInterval: 30_000,                     // optional polling
})

Returns CachedResourceRef<T>:

• value: Signal<T | undefined> — SWR-aware: shows stale data during revalidation
• status: Signal<ResourceStatus> — 'idle'|'loading'|'reloading'|'resolved'|'error'|'local'
• isLoading: Signal<boolean> — true during any fetch
• isStale: Signal<boolean> — true when showing stale data during background refetch
• isInitialLoading: Signal<boolean> — true only on cold cache (use this for spinners)
• error: Signal<unknown>
• hasValue(): boolean
• reload(): boolean
• set(value: T): void — optimistic update, writes through to DataCache (status becomes 'local')
• update(updater: (T | undefined) => T): void — optimistic update, writes through to DataCache
• destroy(): void

cachedMutation<A, R, C>(options)

Mutation wrapper. No injection context needed.

cachedMutation({
  cache: this.#api.cache,
  mutationFn: (order: NewOrder) => this.#api.createOrder(order),
  invalidateKeys: (args, result) => [['orders']],
  onMutate: (args) => { /* optimistic update; return context */ },
  onSuccess: (result, args) => { /* after invalidation */ },
  onError: (error, args, context) => { /* rollback with context */ },
})

Returns CachedMutationRef<A, R>:

• mutate(...args): Promise<R | undefined> — never rejects, errors go to error signal
• status: Signal<CachedMutationStatus> — 'idle'|'pending'|'success'|'error'
• isPending: Signal<boolean>
• error: Signal<unknown>
• data: Signal<R | undefined>
• reset(): void

Void args: when A = void, call mutation.mutate() with no argument.

anyLoading(...signals: Signal<boolean>[]): Signal<boolean>

Combines loading signals. computed(() => signals.some(s => s())). No injection context.

withDevtools(config?)

Feature function for provideZiflux(). Enables CacheRegistry and console logging.

provideZiflux(config, withDevtools({ logOperations: true }))

ZifluxDevtoolsComponent

Standalone component. Selector: <ziflux-devtools />. Auto-hides in production via isDevMode().

SWR Lifecycle

1. Cold cache → loader fires → status: 'loading' → isInitialLoading: true
2. Data arrives → cache.set() → status: 'resolved' → value has data
3. Navigate away → DataCache persists (root-scoped)
4. Navigate back → cache.get() returns fresh → NO loader call → instant render
5. Time passes → entry becomes stale
6. Next read → stale data shown immediately → background refetch starts
   → status: 'reloading' → isStale: true → isInitialLoading: false
7. Fresh data arrives → value updates → isStale: false

The key UX insight: isInitialLoading controls spinners (cold cache only). isStale is informational — stale data is still shown, the user sees content immediately.

Cache Key Design

Keys are string[] serialized via JSON.stringify(). Prefix matching on invalidate() uses JSON.stringify(prefix).slice(0, -1).

// Good: hierarchical keys
['orders', 'list']
['orders', 'details', orderId]
['orders', 'list', JSON.stringify(filters)]

// invalidate(['orders']) → invalidates ALL order-related entries
// invalidate(['orders', 'list']) → invalidates only the list

Gotcha: invalidate(['order']) does NOT match ['orders'] — the JSON prefix ["order" does not match ["orders". This is by design to prevent accidental cross-invalidation.

Empty prefix invalidate([]) is a no-op. Use cache.clear() for full wipe.

Top Anti-Patterns

1. DataCache outside injection context → NG0203. Must be in class field, constructor, or runInInjectionContext.
2. DataCache in route-scoped service → cache dies on navigation, killing SWR. Always providedIn: 'root'.
3. staleTime > expireTime → constructor throws.
4. Expecting invalidate() to delete → it marks stale. get() still returns { data, fresh: false }.
5. invalidate([]) for full wipe → no-op. Use clear().
6. ref.value.set() → value is a read-only Signal, not WritableSignal. Use ref.set() or ref.update().
7. await mutate() then checking success → mutate() never rejects. Check mutation.error() signal or capture return value (undefined = error).
8. Component injecting API service directly → breaks the domain pattern. Component → Store → API.
9. Using Subjects/Observables for state → forbidden. Signals only.
10. Forgetting params: () => undefined suspends → resource stays 'idle', loader never fires.

Optimistic Updates

The onMutate → onError pattern with context:

readonly deleteItem = cachedMutation<string, void, Item[]>({
  mutationFn: (id) => this.#api.deleteItem(id),
  cache: this.#api.cache,
  invalidateKeys: () => [['items']],
  onMutate: (id) => {
    const previous = this.items.value()!;
    this.items.update(items => items!.filter(i => i.id !== id));
    return previous;  // context for rollback
  },
  onError: (_err, _id, previous) => {
    if (previous) this.items.set(previous);  // rollback
  },
});

Concurrent Mutation Semantics

Latest-wins by call order, not resolution order. If two mutate() calls overlap:

• Both run their mutationFn
• Both invalidate the cache on success (server state changed)
• Only the last-invoked call updates signals and fires onSuccess
• Earlier calls' results are silently dropped from signals

Configuration Priority

Constructor arg > provideZiflux() global config > hardcoded defaults (staleTime: 30s, expireTime: 5min).

References

For deeper information, read these reference files:

• references/api-reference.md — Read when you need complete type signatures, all configuration options, DataCacheOptions validation rules, RetryConfig details, CacheInspection shape, or edge-case behaviors.
• references/patterns.md — Read when implementing a new feature with ziflux, setting up optimistic updates, designing cache key hierarchies, configuring polling/retry, or writing the provideZiflux setup.
• references/review-and-debug.md — Read when reviewing code that uses ziflux, debugging cache issues (stale data, missing invalidation, NG0203 errors), writing tests for ziflux code, or cleaning up ziflux usage.