Question

我只是想确保map函数中的代码只应在成功时调用，而不是在失败时调用。

delete(department: Department): Observable<Department[]> {
    return this.post('/delete', body).map(response => {
         let index: number = this.departments.indexOf(department);
         if (index > -1) {
             this.departments.splice(index, 1);
         }
         return this.departments;
     });
}

我不知道map内的代码是否仅在成功时执行。此外，我必须返回Observable，因此我无法在此处应用subscribe功能。

Answer 1

Observable#map运算符仅在成功响应时执行（例如状态200）。 Observable#catch运算符旨在捕获故障。

此外，Observable#catch运算符也会捕获映射成功响应时抛出的javascript错误。例如：

fetchDashboardData(): Observable<Dashboard> {
    return this._http.get(reqUrl, reqOptions)
        .map((response: Response) => new Dashboard(response.json().items[0].dashboard))
        .catch((error: any) => {
            if (error instanceof Error) {
                // js error, e.g. response.json().items was an empty array
                console.log(error); // => “Cannot read property 'dashboard' of undefined...
                return Observable.throw('Incomplete response data!');
            } else {
                return Observable.throw('Server error!');
            }
        });
}

订阅栏：

    this.dashboardService.fetchDashboardData().subscribe(
        (dashboard: Dashboard) => {
            this.dashboard = dashboard;
            console.log('Success fetching dashboard data!', dashboard);
        },
        (errMssg: string) => {
            console.error(errMssg); // => 'Incomplete response data!'
            // or 'Server error!'
        },
        () => {
            // finally block!
        }
    );

如何确保Observable.map仅在成功执行？

1 个答案: