为什么我应该在获取时使用HttpClient? [英] Why should I use HttpClient over fetch?

问题描述

Angular 2+引入了HttpClient，它发出HTTP请求并将其发送到可观察到的RxJS.我的问题是，为什么我会选择使用 HttpClient的API 而不是标准的

Angular 2+ introduces HttpClient which makes an HTTP request and sends them down an RxJS observable. My question is why would I choose to use HttpClient's API over the standard fetch for making single HTTP requests?

我熟悉RxJS，并且了解这张四个基本影响"的图表

I'm familiar with RxJS and I understand this chart of "the four fundamental effects".

       | one        | many
-------------------------------------
sync   |  T         | Iterable<T>
async  | Promise<T> | Observable<T>

Http请求是异步的，并返回一个值.为什么那应该是可观察的?我知道想将事件流组合成HTTP 请求流，但是我不明白为什么我只想使用一个HTTP response 流.难道就不像只有一个值时使用数组吗?

Http requests are async and return one value. Why should that be a Observable? I understand wanting to compose a stream of events into a stream of HTTP requests but I don't understand why I would want to use a stream of just one HTTP response. Isn't that just like using an array when you only have one value?

我错过了什么吗?通常，为什么要使用Angular的HttpClient?哪里不符合条件?

Am I missing something? In general, why should I use Angular's HttpClient? Where does fetch fall short?

推荐答案

这只是一个不同的API.可观察对象有一种更好的方法来分离事物如何流动"(所有运算符:映射，合并，合并等)与执行该方法(.subscribe)相比，这通常有助于获得更好的画面.如果失败，Plus会提供有用的方法来取消或重试该请求.

It's just a different API. Observables have a better way to separate "how things flow" (all operators: map, merge, concat, etc.) vs executing that (.subscribe), which often helps to get a better picture. Plus provides useful methods for cancelling or retrying a request if it fails.

如果需要Promise API(使用async/await，它也非常有用)，则可以始终使用Observable.toPromise()

And you can always use Observable.toPromise() if you need the Promise API (to use async/await, which is really useful as well)

所以对我来说，这只是两种表示同一事物的方法，每种方法都具有另一种优势，但是由于Observable更通用，因此可以使用-您可以从Observable到Promise来回转换，但是Observables带来了很多功能承诺没有的.

So for me it's just two ways of representing the same thing, each one has its advantatges over the other, but as Observable is more generic they used that - You can convert back and forth from Observable to Promise, but Observables bring features that Promises doesn't have.

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