Method constructor

packages/core/src/resource/resource.ts:203–345

(
    request: (ctx: ResourceParamsContext) => R,
    private readonly loaderFn: ResourceStreamingLoader<T, R>,
    defaultValue: T,
    private readonly equal: ValueEqualityFn<T> | undefined,
    private readonly debugName: string | undefined,
    injector: Injector,
    private transferCacheKey: StateKey<T> | undefined,
    getInitialStream?: (request: R) => Signal<ResourceStreamItem<T>> | undefined,
  )

  private readonly transferState: TransferState | undefined;

  constructor(
    request: (ctx: ResourceParamsContext) => R,
    private readonly loaderFn: ResourceStreamingLoader<T, R>,
    defaultValue: T,
    private readonly equal: ValueEqualityFn<T> | undefined,
    private readonly debugName: string | undefined,
    injector: Injector,
    private transferCacheKey: StateKey<T> | undefined,
    getInitialStream?: (request: R) => Signal<ResourceStreamItem<T>> | undefined,
  ) {
    if (isInParamsFunction()) {
      throw invalidResourceCreationInParams();
    }

    super(
      // Feed a computed signal for the value to `BaseWritableResource`, which will upgrade it to a
      // `WritableSignal` that delegates to `ResourceImpl.set`.
      computed(
        () => {
          const streamValue = this.state().stream?.();

          if (!streamValue) {
            return defaultValue;
          }

          // Prevents `hasValue()` from throwing an error when a reload happened in the error state
          if (this.state().status === 'loading' && this.error()) {
            return defaultValue;
          }

          if (!isResolved(streamValue)) {
            throw new ResourceValueError(this.error()!);
          }

          return streamValue.value;
        },
        {equal, ...(ngDevMode ? createDebugNameObject(debugName, 'value') : undefined)},
      ),
      debugName,
    );

    const cacheState = injector.get(CACHE_ACTIVE, undefined, {optional: true}) ?? {isActive: false};

    this.transferState = injector.get(TransferState, undefined, {optional: true}) ?? undefined;

    this.extRequest = linkedSignal<WrappedRequest>(
      () => {
        try {
          setInParamsFunction(true);
          return {request: request(paramsContext), reload: 0};
        } catch (error) {
          rethrowFatalErrors(error);
          if (error === ResourceParamsStatus.IDLE) {
            return {status: 'idle', reload: 0};
          } else if (error === ResourceParamsStatus.LOADING) {
            return {status: 'loading', reload: 0};
          }
          return {error: error as Error, reload: 0};