从 rxjs 导入 Observable 的最佳方法 [英] Best way to import Observable from rxjs
问题描述
在我的 angular 2 应用程序中，我有一个使用 rxjs 库中的 Observable 类的服务.
In my angular 2 app I have a service that uses the Observable class from the rxjs library.
import { Observable } from 'rxjs';
目前我只是使用 Observable 以便我可以使用 toPromise() 函数.
At the moment I am just using Observable so that I can use the toPromise() function.
我在另一个 StackOverflow 问题中读到，以这种方式导入以及从 rxjs/Rx 导入会从 rxjs 库中导入大量不必要的东西增加页面加载时间和/或代码库.
I read in another StackOverflow question somewhere that importing in this way and also importing from rxjs/Rx will import a whole lot of unnecessary stuff from the rxjs library that will increase the page load times and/or the code base.
我的问题是，导入 Observable 以便我可以使用 toPromise() 函数而无需导入其他所有内容的最佳方法是什么?
My question is, what is the best way to import Observable so I can use the toPromise() function without having to import everything else?
推荐答案
Rxjs v 6.*
使用较新版本的 rxjs 简化了它.
Rxjs v 6.*
It got simplified with newer version of rxjs .
import {map} from 'rxjs/operators';
2) 其他
import {Observable,of, from } from 'rxjs';
我们需要管道而不是链接.例如
Instead of chaining we need to pipe . For example
旧语法:
source.map().switchMap().subscribe()
新语法:
source.pipe(map(), switchMap()).subscribe()
注意:由于名称与 JavaScript 保留字发生冲突，一些运算符的名称发生了变化！其中包括:
Note: Some operators have a name change due to name collisions with JavaScript reserved words! These include:
do -> tap,
catch -> catchError
switch -> switchAll
finally -> finalize
我写这个答案部分是为了帮助自己，因为我每次需要导入操作符时都会检查文档.如果有什么可以做得更好的方法，请告诉我.
I am writing this answer partly to help myself as I keep checking docs everytime I need to import an operator . Let me know if something can be done better way.
这会导入整个库.那么你就不用担心加载每个 operator 了.但是你需要附加 Rx.我希望 tree-shaking 能够优化并只选择需要的函数(需要验证) 正如评论中提到的，tree-shaking 无济于事.所以这不是优化的方式.
This imports the entire library. Then you don't need to worry about loading each operator . But you need to append Rx. I hope tree-shaking will optimize and pick only needed funcionts( need to verify ) As mentioned in comments , tree-shaking can not help. So this is not optimized way.
public cache = new Rx.BehaviorSubject('');
<小时>
或者您可以导入单个运算符.
这将优化您的应用以仅使用这些文件:
这种语法通常用于主对象，如Rx本身或Observable等，
This syntax usually used for main Object like Rx itself or Observable etc.,
可以用这种语法导入的关键字
Keywords which can be imported with this syntax
Observable, Observer, BehaviorSubject, Subject, ReplaySubject
3) import 'rxjs/add/observable/__________';
Angular 5 的更新
使用 Angular 5，它使用 rxjs 5.5.2+
With Angular 5, which uses rxjs 5.5.2+
import { empty } from 'rxjs/observable/empty';
import { concat} from 'rxjs/observable/concat';
这些通常直接与 Observable 一起使用.例如
These are usually accompanied with Observable directly. For example
Observable.from()
Observable.of()
可以使用此语法导入的其他此类关键字:
Other such keywords which can be imported using this syntax:
concat, defer, empty, forkJoin, from, fromPromise, if, interval, merge, of,
range, throw, timer, using, zip
4) import 'rxjs/add/operator/_________';
Angular 5 的更新
使用 Angular 5，它使用 rxjs 5.5.2+
With Angular 5, which uses rxjs 5.5.2+
import { filter } from 'rxjs/operators/filter';
import { map } from 'rxjs/operators/map';
这些通常在创建 Observable 之后进入流中.就像这段代码片段中的 flatMap:
These usually come in the stream after the Observable is created. Like flatMap in this code snippet:
Observable.of([1,2,3,4])
.flatMap(arr => Observable.from(arr));
使用此语法的其他此类关键字:
Other such keywords using this syntax:
audit, buffer, catch, combineAll, combineLatest, concat, count, debounce, delay,
distinct, do, every, expand, filter, finally, find , first, groupBy,
ignoreElements, isEmpty, last, let, map, max, merge, mergeMap, min, pluck,
publish, race, reduce, repeat, scan, skip, startWith, switch, switchMap, take,
takeUntil, throttle, timeout, toArray, toPromise, withLatestFrom, zip
平面地图:flatMap 是mergeMap 的别名，所以我们需要导入mergeMap 来使用flatMap.
FlatMap:
flatMap is alias to mergeMap so we need to import mergeMap to use flatMap.
/add 导入的注意事项:
Note for /add imports :
我们只需要在整个项目中导入一次.所以建议在一个地方做.如果它们包含在多个文件中，并且其中一个被删除，则构建将因错误原因而失败.
We only need to import once in whole project. So its advised to do it at a single place. If they are included in multiple files, and one of them is deleted, the build will fail for wrong reasons.
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