从 RxJS5 升级到 RxJS6

Question

我在从 RxJS5 升级到版本 6 时遇到问题。我有以下代码：

  private captureEvents(canvasEl: HTMLCanvasElement) {

    Observable
      .fromEvent(canvasEl, 'mousedown')
      .switchMap((e) => {
        return Observable
          .fromEvent(canvasEl, 'mousemove')
          .takeUntil(Observable.fromEvent(canvasEl, 'mouseup'))
          .pairwise()
      })
      .subscribe((res: [MouseEvent, MouseEvent]) => {
        const rect = canvasEl.getBoundingClientRect();

        const prevPos = {
          x: res[0].clientX - rect.left,
          y: res[0].clientY - rect.top
        };

        const currentPos = {
          x: res[1].clientX - rect.left,
          y: res[1].clientY - rect.top
        };

        this.drawOnCanvas(prevPos, currentPos);
      });
  }

但是当我升级到 RxJS6 时，出现以下错误：

Property 'fromEvent' does not exist on type 'typeof Observable'.

我试图从这个 (RxJS5) 更改我的导入：

import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/fromEvent';
import 'rxjs/add/operator/takeUntil';
import 'rxjs/add/operator/pairwise'; 
import 'rxjs/add/operator/switchMap';

对此（RxJS6）：

import { Observable, fromEvent } from 'rxjs';
import { switchMap, takeUntil, pairwise } from 'rxjs/operators';

这是我升级代码的最佳尝试：

  private captureEvents(canvasEl: HTMLCanvasElement) {

    const obsMouseDown = fromEvent(canvasEl, 'mousedown').pipe(
      switchMap((e) => {
        const obsMouseMove = fromEvent(canvasEl, 'mousemove').pipe(
          takeUntil(a => {
            const obsMouseUp = fromEvent(canvasEl, 'mouseup').pipe(
              pairwise()
            );
            return obsMouseUp;
          }));

        return obsMouseMove;
      }))
      .subscribe((res: [MouseEvent, MouseEvent]) => {
        const rect = canvasEl.getBoundingClientRect();

        const prevPos = {
          x: res[0].clientX - rect.left,
          y: res[0].clientY - rect.top
        };

        const currentPos = {
          x: res[1].clientX - rect.left,
          y: res[1].clientY - rect.top
        };

        this.drawOnCanvas(prevPos, currentPos);
      });
  }

但这不起作用 - 我收到 "takeUntil" 代码的错误：

Argument of type '(a: any) => Observable<[Event, Event]>' is not assignable to parameter of type 'Observable'

plnkr 原始代码示例：
https://embed.plnkr.co/QSvJxi/

Answer 1

fromEvent

现在已经是 Observable 类型了。您不需要将它链接到 Obserbal，而是可以直接调用它并将其影响到变量或更好的常量。如下图：

const source = fromEvent(document, 'click');

关于导入，你猜对了

import { fromEvent } from 'rxjs';

Answer 2

出于某种原因，您的 plnkr 对我不起作用，但我会尽力提供答案。我认为你应该在这里做两件事作为开始。尝试初始化您的 Observables，以便像这样调用和订阅它们更容易：

const mousedown$ = fromEvent(pauseButton, 'mousedown');
const mouseup$ = fromEvent(resumeButton, 'mouseup');
const mousemove$ = fromEvent(resumeButton, 'mousemove');

第二件事你现在应该使用 Rxjs 5 和 6 来管理你的操作员，就像这样，并订阅你所有的事件

mousedown$.pipe(
    switchMap(res => {
       mousemove$.pipe(//Whatever Operators and subscribitions to other events).subscribe(...)
    }),
    map(// Whatever you want back from your event)
  ).subscribe(...)

我指的是文档链接 switchMap && takeUntil。由于 Rxjs 中的许多语法正在发生变化，请不要羞于浏览文档，没有比这更好的了。

Answer 3

我认为你实际上非常接近，我认为你也有你的管道 "deep" 不过 - 请记住，你可以根据需要在管道中将任意数量的运算符链接在一起，所以你的内部鼠标移动直到-mouse-up switchmap 应该看起来更像这样：

private captureEvents(canvasEl: HTMLCanvasElement) {

    const obsMouseDown = fromEvent(canvasEl, 'mousedown').pipe(
        switchMap((e) => {
            return fromEvent(canvasEl, 'mousemove').pipe(
              takeUntil(a => fromEvent(canvasEl, 'mouseup')),
              pairwise()
            ));
        }))
        .subscribe((res: [MouseEvent, MouseEvent]) => {
            // snip
        });
}

从 RxJS5 升级到 RxJS6

Upgrading from RxJS5 to RxJS6

observable

rxjs5

angular5

angular6

rxjs6