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非同期ローカルストレージオブザーバブルをプロミスに変換して正しくキャストするにはどうすればよいですか？角型非同期ローカルストレージプロミスが空を解決する
私は角非同期ローカルストレージのプロジェクトを使用して、いくつかのサービスデータをキャッシュしようとしています： https://github.com/cyrilletuzi/angular-async-local-storage
データはローカルIndexDb（私はクローム開発ツールでそれを見て）に適切に保存されます。問題はデータを取り戻すことができないことです。約束は空になる。これは問題の行です：
result => this._storage.getItem（this._objectKey）.toPromise（）;
ここでは、完全なソースへのリンクです： https://github.com/GregFinzer/AmbientStateExample
ここでは、キャッシングとフルサービスのクラスです：非同期角度ストレージの
// 3rd party imports
import { Injectable } from '@angular/core';
import { Http, Response, RequestOptions, Headers } from '@angular/http';
import { Observable, Subscription } from 'rxjs/Rx';
import { AsyncLocalStorage } from 'angular-async-local-storage';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/toPromise';
import 'rxjs/add/operator/do';
import {OnInit, OnDestroy} from '@angular/core';
// Our imports
import { Stock } from './stock-model';
@Injectable()
export class StockService {
private _url = 'http://finance.google.com/finance/info?client=ig&q=NASDAQ%3AAAPL,GOOG';
private _stocks: Promise<Stock[]>;
private _timer;
private _sub: Subscription;
private _lastStockCheckDate: Date;
private _objectKey = 'stocksObject';
private _dateKey = 'lastStockCheckDate';
private _tickInterval = 60000; // sixty seconds
constructor(private _http: Http, protected _storage: AsyncLocalStorage) {
this._timer = Observable.timer(this._tickInterval, this._tickInterval);
this._sub = this._timer.subscribe(t => { this.timerInterval(t); });
}
// This will not be hit, not sure how to implement in a service
ngOnDestroy() {
console.log('Destroy timer');
this._sub.unsubscribe();
}
timerInterval(tick) {
console.log('Interval hit: ' + tick);
this.processCache();
}
// Get the stocks from the actual service or from local storage cache
public getStockCache(): Promise<Stock[]> {
console.error('getStockCache()');
let result: Promise<Stock[]>;
// Call the service if we have not before
if (!this._lastStockCheckDate) {
result = this.getStocks();
this.saveToStorage(result);
this.updateLastCheckDate();
} else {
// Get the data from storage
result = <Promise<Stock[]>> this._storage.getItem(this._objectKey).toPromise();
}
return result;
}
private processCache(): void {
console.log('processCache()');
this._storage.getItem(this._dateKey).subscribe((lastStockCheckDate) => {
let now = new Date();
// Google has a maximum of 60 seconds between calls
if (lastStockCheckDate && (now.getTime() - lastStockCheckDate.getTime()) < this._tickInterval) {
return;
}
// Save the last check date
this.updateLastCheckDate();
// Get the stocks from the service
let serviceStockPromise: Promise<Stock[]> = this.getStocks();
// If anything changed, save to local storage
serviceStockPromise.then((serviceStocks) => {
this._storage.getItem(this._objectKey).subscribe((storageStocks) => {
if (this.anythingChanged(serviceStocks, storageStocks)) {
this._storage.setItem(this._objectKey, serviceStocks)
.subscribe(() => {},() => {});
}
},() => {});
});
},() => {});
}
// Has anything changed from what was returned from the service vs what we have in local storage?
private anythingChanged(serviceStocks: Stock[], storageStocks: Stock[]): boolean {
console.log('anythingChanged()');
if (serviceStocks.length !== storageStocks.length) {
return true;
}
for (let i = 0; i < serviceStocks.length; i++) {
if (serviceStocks[i].l_cur !== storageStocks[i].l_cur) {
return true;
}
}
return false;
}
// Save what was returned from the service into local storage asynchronously
private saveToStorage(stocks: Promise<Stock[]>): void {
console.error('saveToStorage()');
stocks.then((data) => {
this._storage.setItem(this._objectKey, data)
.subscribe(() => {},() => {});
});
}
// Update the last time we called the service
private updateLastCheckDate(): void {
console.error('updateLastCheckDate()');
const now = new Date();
this._lastStockCheckDate = now;
this._storage.setItem(this._dateKey, now).subscribe(() => {},() => {});
}
// Get stocks from the service
private getStocks(): Promise<Stock[]> {
console.error('getStocks()');
return this._http.get(this._url, this.getRequestOptions())
.do((data: Response) => console.log('All: ' + data.text()))
// The substr is required because Google puts in two comment characters //
.map((response: Response) => <Stock[]> JSON.parse(response.text().substr(3)))
.toPromise();
}
// Write any errors out to the console
private handleError(error: Response) {
console.error(error);
let msg = `Error status code ${error.status} at ${error.url}`;
return Observable.throw(msg);
}
// Ensure we get JSON from the service
private getRequestOptions(): RequestOptions {
let opt: RequestOptions;
let myHeaders: Headers = new Headers;
myHeaders.append('Accept', 'application/json');
opt = new RequestOptions();
opt.headers = myHeaders;
return opt;
}
}