Question

我在扩展Observables服务后从本地存储返回数据。

方案：组件将订阅Service.GetAll（）和GetAll（）将在localStorage中查找数据，如果发现它将返回，否则它将进行api调用以获取数据。

我设法使用Promise，但我更喜欢将其转换为Observables

getAll(): Promise<IScheduleFrequency[]> {
    let ScheduleFrequencies: IScheduleFrequency[] = this.storageService.get('ScheduleFrequencies');
    if (ScheduleFrequencies != null) {
        return Promise.resolve(ScheduleFrequencies);
    } else {
        return this.http.get(this.apiUrl)
            .toPromise()
            .then((response) => {
                let ScheduleFrequencies: IScheduleFrequency[] = response.json();
                this.storageService.save('ScheduleFrequencies', activityScheduleFrequencies);
                return ScheduleFrequencies || [];
            })
            .catch(this.handleError);
    }
}

如果有人可以告诉我如何延伸到服务以下来做同样的事情。

getAll(): Observable<TransactionStatus[]> {
    return this.http.get(this.apiUrl)
        .map(this.extractData)
        .catch(this.handleError);
}

谢谢 Asanka

更新谢谢@ nzjun90的回复工作需要导入'of' import'rxjs / add / observable / of';

Answer 1

如果您需要澄清，请告诉我。

getAll(): Observable<TransactionStatus[]> {
    let ScheduleFrequencies: IScheduleFrequency[] = this.storageService.get('ScheduleFrequencies');

    if (ScheduleFrequencies != null) {
        return Observable.of(ScheduleFrequencies);
    }

    return this.http.get(this.apiUrl)
    .map((response)=>{
              let ScheduleFrequencies: IScheduleFrequency[] = response.json();
              this.storageService.save('ScheduleFrequencies', activityScheduleFrequencies);
              return ScheduleFrequencies || [];
    }).catch( e => {return this.handleError});
}

Angular 2 Observable Service从localStorage返回数据

1 个答案: