Question

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：

类型为“可观察的类型”的属性“ fromEvent”不存在。

我试图从此（RxJS5）更改导入：

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);
      });
  }

但这无法正常工作-我收到“ takeUntil”代码的错误：

类型'（a：any）=> Observable <[Event，Event]>'的参数不是可分配给“可观察”类型的参数

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

Answer 1

fromEvent

现在已经是Observable类型。您不需要将其链接到Observebal，而是可以直接调用它并将其影响到变量或更好的const。如下所示：

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

对于导入，您认为正确

import { fromEvent } from 'rxjs';

Answer 2

由于某种原因，您的plnkr不适用于我，但我会尽力提供答案。我认为您应该在这里做2件事。尝试初始化您的Observable，以便像这样轻松地调用它们并进行订阅：

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

第二点，您现在应该像这样用Rxjs 5和6来传递操作员，并订阅所有事件

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中的许多语法都在变化，因此不要羞于浏览文档，没有什么比这更好的了。

Answer 3

我认为您实际上非常接近，但我认为您的管道太“深”了-请记住，您可以在管道中将所需的多个运算符链接在一起，因此内部鼠标可以移动直到鼠标移开switchmap应该看起来像这样：

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

3 个答案: