TypeScript BehaviorSubject.distinctUntilChanged方法代碼示例

function StoreService(): D1StoreServiceType {
  'ngInject';

  let _stores: D1Store[] = [];

  // A subject that keeps track of the current account. Because it's a
  // behavior subject, any new subscriber will always see its last
  // value.
  const accountStream = new BehaviorSubject<DestinyAccount | null>(null);

  // The triggering observable for force-reloading stores.
  const forceReloadTrigger = new Subject();

  // A stream of stores that switches on account changes and supports reloading.
  // This is a ConnectableObservable that must be connected to start.
  const storesStream = accountStream
    // Only emit when the account changes
    .distinctUntilChanged(compareAccounts)
    // But also re-emit the current value of the account stream
    // whenever the force reload triggers
    .merge(forceReloadTrigger.switchMap(() => accountStream.take(1)))
    // Whenever either trigger happens, load stores
    .switchMap(loadingTracker.trackPromise(loadStores))
    // Keep track of the last value for new subscribers
    .publishReplay(1);

  // TODO: If we can make the store structures immutable, we could use
  //       distinctUntilChanged to avoid emitting store updates when
  //       nothing changed!

  const service = {
    getActiveStore: () => _stores.find((s) => s.current),
    getStores: () => _stores,
    getStore: (id) => _stores.find((s) => s.id === id),
    getVault: () => _stores.find((s) => s.isVault) as D1Vault | undefined,
    getAllItems: () => _.flatMap(_stores, (s) => s.items),
    refreshRatingsData() {
      return;
    },
    getStoresStream,
    getItemAcrossStores,
    updateCharacters,
    reloadStores,
    touch() {
      store.dispatch(update({ stores: _stores }));
    }
  };

  return service;

  /**
   * Find an item among all stores that matches the params provided.
   */
  function getItemAcrossStores(params: {
    id?: string;
    hash?: number;
    notransfer?: boolean;
    amount?: number;
  }) {
    const predicate = _.iteratee(_.pick(params, 'id', 'hash', 'notransfer', 'amount')) as (
      i: DimItem
    ) => boolean;
    for (const store of _stores) {
      const result = store.items.find(predicate);
      if (result) {
        return result;
      }
    }
    return undefined;
  }

  /**
   * Update the high level character information for all the stores
   * (level, light, int/dis/str, etc.). This does not update the
   * items in the stores - to do that, call reloadStores.
   */
  function updateCharacters(account: DestinyAccount) {
    // TODO: the router.globals.params defaults are just for now, to bridge callsites that don't know platform
    if (!account) {
      if (router.globals.params.membershipId && router.globals.params.platformType) {
        account = {
          membershipId: router.globals.params.membershipId,
          platformType: router.globals.params.platformType,
          displayName: 'Unknown',
          platformLabel: 'Unknown',
          destinyVersion: 1
        };
      } else {
        throw new Error("Don't know membership ID and platform type");
      }
    }

    return Promise.all([getDefinitions(), getCharacters(account)]).then(([defs, bungieStores]) => {
      _stores.forEach((dStore) => {
        if (!dStore.isVault) {
          const bStore = bungieStores.find((s) => s.id === dStore.id)!;
          dStore.updateCharacterInfo(defs, bStore.base);
        }
      });
      service.touch();
//.........這裏部分代碼省略.........

import { BehaviorSubject } from 'rxjs/BehaviorSubject';
import '../rx-operators';
import { IPromise, IDeferred } from 'angular';

const subject = new BehaviorSubject(false);

export const loadingTrackerStream = subject.distinctUntilChanged().shareReplay(1);

export default function loadingTracker(promiseTracker) {
  'ngInject';

  const tracker = promiseTracker();

  return {
    addPromise(promise: IPromise<any>) {
      const fullPromise: IDeferred<any> = tracker.addPromise(promise);
      subject.next(true);
      fullPromise.promise.finally(() => {
        setTimeout(() => subject.next(this.active()), 0);
      });
    },

    active() {
      return tracker.active();
    }
  };
}

/**
 * TODO: For now this is a copy of StoreService customized for D2. Over time we should either
 * consolidate them, or at least organize them better.
 */
function makeD2StoresService(): D2StoreServiceType {
  'ngInject';

  let _stores: D2Store[] = [];

  // A subject that keeps track of the current account. Because it's a
  // behavior subject, any new subscriber will always see its last
  // value.
  const accountStream = new BehaviorSubject<DestinyAccount | null>(null);

  // The triggering observable for force-reloading stores.
  const forceReloadTrigger = new Subject();

  // A stream of stores that switches on account changes and supports reloading.
  // This is a ConnectableObservable that must be connected to start.
  const storesStream = accountStream
    // Only emit when the account changes
    .distinctUntilChanged(compareAccounts)
    // But also re-emit the current value of the account stream
    // whenever the force reload triggers
    .merge(forceReloadTrigger.switchMap(() => accountStream.take(1)))
    // Whenever either trigger happens, load stores
    .switchMap(loadStores)
    // Keep track of the last value for new subscribers
    .publishReplay(1);

  // TODO: If we can make the store structures immutable, we could use
  //       distinctUntilChanged to avoid emitting store updates when
  //       nothing changed!

  const service = {
    getActiveStore: () => _stores.find((s) => s.current),
    getStores: () => _stores,
    getStore: (id: string) => _stores.find((s) => s.id === id),
    getVault: () => _stores.find((s) => s.isVault) as D2Vault | undefined,
    getAllItems: () => flatMap(_stores, (s) => s.items),
    getStoresStream,
    getItemAcrossStores,
    updateCharacters,
    reloadStores,
    refreshRatingsData,
    touch() {
      store.dispatch(update(_stores));
    }
  };

  return service;

  /**
   * Find an item among all stores that matches the params provided.
   */
  function getItemAcrossStores(params: {
    id?: string;
    hash?: number;
    notransfer?: boolean;
    amount?: number;
  }) {
    const predicate = _.iteratee(_.pick(params, 'id', 'hash', 'notransfer', 'amount')) as (
      i: DimItem
    ) => boolean;
    for (const store of _stores) {
      const result = store.items.find(predicate);
      if (result) {
        return result;
      }
    }
    return undefined;
  }

  /**
   * Update the high level character information for all the stores
   * (level, light, int/dis/str, etc.). This does not update the
   * items in the stores - to do that, call reloadStores.
   */
  function updateCharacters(account: DestinyAccount): IPromise<D2Store[]> {
    // TODO: the router.globals.params defaults are just for now, to bridge callsites that don't know platform
    if (!account) {
      if (router.globals.params.membershipId && router.globals.params.platformType) {
        account = {
          membershipId: router.globals.params.membershipId,
          platformType: router.globals.params.platformType,
          displayName: 'Unknown',
          platformLabel: 'Unknown',
          destinyVersion: 2
        };
      } else {
        throw new Error("Don't know membership ID and platform type");
      }
    }

    return $q
      .all([getDefinitions(), getCharacters(account)])
      .then(([defs, profileInfo]: [D2ManifestDefinitions, DestinyProfileResponse]) => {
        // TODO: create a new store
        _stores.forEach((dStore) => {
          if (!dStore.isVault) {
//.........這裏部分代碼省略.........

function VendorService(): VendorServiceType {
  let _ratingsRequested = false;

  const service: VendorServiceType = {
    vendorsLoaded: false,
    getVendorsStream,
    reloadVendors,
    getVendors() {
      return this.vendors;
    },
    // By hash
    vendors: {},
    totalVendors: 0,
    loadedVendors: 0,
    requestRatings,
    countCurrencies
    // TODO: expose getVendor promise, idempotently?
  };

  // A subject that keeps track of the current account. Because it's a
  // behavior subject, any new subscriber will always see its last
  // value.
  const accountStream = new BehaviorSubject<DestinyAccount | null>(null);

  // A stream of stores that switches on account changes and supports reloading.
  // This is a ConnectableObservable that must be connected to start.
  const vendorsStream = accountStream
    // Only emit when the account changes
    .distinctUntilChanged(compareAccounts)
    .do(() => {
      service.vendors = {};
      service.vendorsLoaded = false;
    })
    .switchMap(
      (account) => D1StoresService.getStoresStream(account!),
      (account, stores) => [account!, stores!]
    )
    .filter(([_, stores]) => Boolean(stores))
    .switchMap(([account, stores]: [DestinyAccount, D1Store[]]) => loadVendors(account, stores))
    // Keep track of the last value for new subscribers
    .publishReplay(1);

  const clearVendors = _.once(() => {
    D1ManifestService.newManifest$.subscribe(() => {
      service.vendors = {};
      service.vendorsLoaded = false;
      deleteCachedVendors();
    });
  });

  return service;

  function deleteCachedVendors() {
    // Everything's in one table, so we can't just clear
    keys().then((keys) => {
      keys.forEach((key) => {
        if (key.toString().startsWith('vendor')) {
          del(key);
        }
      });
    });
  }

  /**
   * Set the current account, and get a stream of vendor and stores updates.
   * This will keep returning data even if something else changes
   * the account by also calling "vendorsStream". This won't force the
   * vendors to reload unless they haven't been loaded at all.
   *
   * @return a stream of vendor updates
   */
  function getVendorsStream(account: DestinyAccount) {
    accountStream.next(account);
    // Start the stream the first time it's asked for. Repeated calls
    // won't do anything.
    vendorsStream.connect();
    clearVendors(); // Install listener to clear vendors
    return vendorsStream;
  }

  function reloadVendors() {
    D1StoresService.reloadStores();
  }

  /**
   * Returns a promise for a fresh view of the vendors and their items.
   */
  function loadVendors(
    account: DestinyAccount,
    stores: D1Store[]
  ): Promise<[D1Store[], { [vendorHash: number]: Vendor }]> {
    const characters = stores.filter((s) => !s.isVault);

    const reloadPromise = getDefinitions()
      .then((defs) => {
        // Narrow down to only visible vendors (not packages and such)
        const vendorList = Object.values(defs.Vendor).filter((v) => v.summary.visible);

        service.totalVendors = characters.length * (vendorList.length - vendorBlackList.length);
        service.loadedVendors = 0;
//.........這裏部分代碼省略.........