Angular2依赖注入抽象类
我在互联网上查找一个随机角度问题的解决方案,遇到了以下示例:Angular2依赖注入抽象类,angular,dependency-injection,abstract-class,Angular,Dependency Injection,Abstract Class,我在互联网上查找一个随机角度问题的解决方案,遇到了以下示例: export class AppModule { constructor(private router: Router, private viewportScroller: ViewportScroller) { this.router.events.pipe( filter((e: Event): e is Scroll => e instanceof Scroll), pairwise()
export class AppModule {
constructor(private router: Router, private viewportScroller: ViewportScroller) {
this.router.events.pipe(
filter((e: Event): e is Scroll => e instanceof Scroll),
pairwise()
).subscribe((e: Scroll[]) => {
const previous = e[0];
const current = e[1];
if (current.position) {
this.viewportScroller.scrollToPosition(current.position);
} else if (current.anchor) {
this.viewportScroller.scrollToAnchor(current.anchor);
} else ...
...
ViewportScroller是一个抽象类。我试图理解Angular中的依赖注入。如何使抽象类可注入?将注入的是扩展ViewportScroller的实际类。Interfacets也可以用作注入口。将被注入的是由某些提供者提供的给定接口的实现您可以注入一个具有具体实现的抽象类 以下是如何在Angular中定义ViewportScroller: 然后,它由BrowserViewportScroller实现:
/**
* Defines a scroll position manager. Implemented by `BrowserViewportScroller`.
*/
export abstract class ViewportScroller {
// De-sugared tree-shakable injection
// See #23917
/** @nocollapse */
static ɵprov = ɵɵdefineInjectable({
token: ViewportScroller,
providedIn: 'root',
factory: () => new BrowserViewportScroller(ɵɵinject(DOCUMENT), window)
});
...
/**
* Manages the scroll position for a browser window.
*/
export class BrowserViewportScroller implements ViewportScroller {
private offset: () => [number, number] = () => [0, 0];
constructor(private document: Document, private window: Window) {}
...