由于 Http 类的 post 方法返回一个 observable，你需要订阅它才能执行它的初始化处理.Observable 是惰性的.

Since the post method of the Http class returns an observable you need to subscribe it to execute its initialization processing. Observables are lazy.

您应该观看此视频以了解更多详情:

You should have a look at this video for more details:

• https://egghead.io/lessons/rxjs-rxjs-observables-vs-promises