[英]how to implement rxjs subscription in angular 2?
我有一个带有以下代码的服务:
import {Injectable} from 'angular2/core';
import {Observable} from 'rxjs/Observable';
import {Observer} from 'rxjs/Observer';
import 'rxjs/add/operator/share';
import {Article} from './article';
@Injectable()
export class ArticleService {
public articleSelected$: Observable<Article>;
private _observer: Observer<Article>;
constructor() {
this.articleSelected$ = new Observable(observer =>
this._observer = observer).share();
}
selectArticle(article:Article){
this._observer.next(article);
}}
在我的组件中:
export class seeArticle{
subscription: any;
constructor(private _articleService: ArticleService) {
}
ngOnInit() {
this.subscription = this._articleService.articleSelected$
.subscribe(article => this.onArticleSelected(article));
}
onArticleSelected(article){
console.log("an article was selected",article);
}
}
当我在另一个组件中选择一篇文章(通过点击它)时,selectArticle 服务函数被执行,没有问题。 但是, this._observer.next(article);
似乎触发了以下错误:
"TypeError: Cannot read property 'next' of undefined"
作为 angular 2 和 Rxjs 的新手,我无法弄清楚
与您的代码的问题是, this._observer
时尚不可用selectArticle
方法被调用,因为
observer => this._observer = observer
部分是异步的。
因此,不要手动创建 Observable,而是使用为您正确包装 Observable 的EventEmitter :
@Injectable()
export class ArticleService {
public articleSelected$: EventEmitter<Article>;
constructor() {
this.articleSelected$ = new EventEmitter();
}
selectArticle(article:Article){
this.articleSelected$.next(article);
}
}
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