我遇到了一个问题,当我手动输入 localhost:4200/create 时,它会出现在我想要它去的页面上,但是当我单击链接将我带到那里时,我收到一条错误消息:
TypeError: Cannot read property 'unsubscribe' of undefined
at PostListComponent.ngOnDestroy
这是我的代码:
header.component.html
<mat-toolbar color="primary">
<span><a routerLink="/">My Messages</a></span>
<ul>
<li><a routerLink="/create">New Post</a></li>
</ul>
</mat-toolbar>
app-routing.module.ts:
import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';
import { PostCreateComponent } from './posts/post-create/post-create.component';
import { PostListComponent } from './posts/post-list/post-list.component';
const routes: Routes = [
{path: '', component: PostListComponent},
{path: 'create', component: PostCreateComponent},
];
@NgModule({
imports: [RouterModule.forRoot(routes)],
exports: [RouterModule]
})
export class AppRoutingModule { }
postlistcomponent.ts
import { Component, OnDestroy, OnInit } from '@angular/core';
import { Subscription } from 'rxjs';
import { Post } from '../posts';
import { PostsService } from '../posts.service';
@Component({
selector: 'app-post-list',
templateUrl: './post-list.component.html',
styleUrls: ['./post-list.component.css'],
})
export class PostListComponent implements OnInit, OnDestroy {
posts: Post[] = [];
private postsSub: Subscription;
constructor(public postsService: PostsService) {}
ngOnInit(): void {
this.postsService.getPosts();
this.postsService.getPostUpdateListener().subscribe((posts: Post[]) => {
this.posts = posts;
});
}
onDelete(postId: string) {
this.postsService.deletePost(postId);
}
ngOnDestroy() {
this.postsSub.unsubscribe();
}
}
答案 0 :(得分:3)
就像错误所说的那样,您正在对 unsubscribe
中不存在的对象调用 PostListComponent
(postlist.component.ts?)
在该文件中,找到 ngOnDestroy
函数,对于任何 this.object$.unsubscribe()
函数,首先测试对象 -
if (this.object$ && !this.object$.closed) {
this.object$.unsubscribe()
}
我以 this.object$
为例 - 您的变量将被称为不同的名称
答案 1 :(得分:1)
当您从 /
导航到 /create
时,ngOnDestroy
中的 PostListComponent
会引发错误。
这就是为什么它发生在链接上而不是当你输入网址时。
答案 2 :(得分:1)
正如您在 ngInit 中看到的,您没有将任何值传递给您的变量 (postsSub)。这就是为什么你不能摧毁它。
改变这个:
ngOnInit(): void {
this.postsService.getPosts();
this.postsService.getPostUpdateListener().subscribe((posts: Post[]) => {
this.posts = posts;
});
}
为此:
ngOnInit(): void {
this.postsService.getPosts();
this.postsSub = this.postsService.getPostUpdateListener().subscribe((posts: Post[]) => {
this.posts = posts;
});
}
应该可以。
问候