[英]Angular 4 RxJs Observable Subjects array not updating with new object
因此,最近我了解了主题,并试图在个人项目中使用它们。 我有一个从json文件中获取数据并将其转换为“ Article”类型的服务。 文章是一个自定义类,用于保存有关博客文章的信息。
我这里的最终目标是获取此文章数组,然后当我按+按钮时,它将新的空白Article添加到当前列表中,并且该视图应通过显示具有一些默认值的空白文章来表示它。 这不会保留(另存为json)新的空白文章,而只是将其添加到当前列表中,以便视图更新并显示它。 保存将在以后。
我无法一辈子都可以使用它。 所有文章都正确显示在我的“文章列表”页面上,但是手动将空白文章推送到它似乎根本没有任何作用。
这是我的服务档案
@Injectable()
export class ArticleService {
headers: Headers;
options: RequestOptions;
articles: ReplaySubject<Article[]>;
private url = 'data/articles.json';
constructor(private http: Http) {
this.headers = new Headers({ 'Content-Type': 'application/json' });
this.options = new RequestOptions({ headers: this.headers });
this.articles = new ReplaySubject<Article[]>();
}
/**
* fetch a list of articles
*/
getArticles(): Observable<Article[]> {
// no articles fetched yet, go get!
return this.http.get(this.url, this.options)
.map(response => <Article[]>response.json())
.do(data => this.articles.next(data))
.catch(this.handleError);
}
/**
* add a new article to the list
* @param article
*/
addArticle(article: any): void {
this.getArticles().take(1).subscribe(current => {
//
//
// THIS WORKS. this.articles is UPDATED successfully, but the view doesn't update
// IT ALSO LOOKS LIKE this.articles may be being reset back to the result of the get()
// and losing the new blank article.
//
//
current.push(article);
this.articles.next(current);
});
}
...
}
而且我有一个列表组件像这样更新列表:
export class ArticleListComponent implements OnInit {
articles: Article[];
public constructor(private articleService: ArticleService) { }
ngOnInit(): void {
this.getArticles();
}
getArticles(): void {
this.articleService.getArticles().subscribe(articles => this.articles = articles);
}
}
另一个创建新的空白文章的组件:
export class CreatorComponent {
articles: Article[];
public constructor(private articleService: ArticleService) { }
/**
* add a new empty article
*/
add(): void {
let article = {};
article['id'] = 3;
article['author'] = "Joe Bloggs";
article['category'] = "Everyday";
article['date'] = "November 22, 2017"
article['image'] = "/assets/images/post-thumb-m-1.jpg";
article['slug'] = "added-test";
article['title'] = "New Via Add";
article['content'] = "Minimal content right now, not a lot to do."
this.articleService.addArticle(article);
}
}
我可以调试,并且服务上的this.articles属性似乎已使用新的空白文章进行了更新,但是视图并没有改变,我不能肯定地说,但是似乎该文章很快就丢失了无论如何尽快添加。 可观察到的重复http get和擦洗文章列表是否再次干净?
您实际上尚未在显示组件中订阅您感兴趣的主题。 您只订阅http呼叫,该呼叫会填充您感兴趣的主题,然后终止。 像这样尝试一下:
private articleSub: Subscription;
ngOnInit(): void {
this.articleSub = this.articleService.articles.subscribe(articles => this.articles = articles);
this.articleService.getArticles().subscribe();
}
ngOnDestroy() { //make sure component implements OnDestroy
this.articleSub.unsubscribe(); // always unsubscribe from persistent observables to avoid memory leaks
}
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