[英]ERROR TypeError: Cannot read property '0' of undefined at Object.eval [as updateRenderer] using {{myvideo[currentSlideIndex]?.title}}
[英]Cannot read property 'title' of undefined at Object.eval [as updateRenderer]
我正在尝试获取单个帖子的详细信息,但我不断收到此错误; 错误类型错误:无法读取 Object.eval [as updateRenderer] 中未定义的属性“title”。 虽然数据在 console.log 中被正确获取,但它没有显示在页面本身上。 当我执行 {{post?.title}} 时,错误消失了,但结果仍然没有出现在页面上,但在 console.log 中正确显示
离子框架:v4 操作系统平台:Windows 10
售后服务
getAllPosts(): Observable<any> {
return this.http.get(`${this.url}`).pipe(
map(results => {
console.log('Raw: ', results);
return results['posts'];
})
);
}
getPost(postId: string) {
return this.http.get(`${this.url}/${postId}`);
}
post.page.ts
import { Component, OnInit } from '@angular/core';
import { ActivatedRoute } from '@angular/router';
import { PostService } from '../post.service';
@Component({
selector: 'app-post',
templateUrl: './post.page.html',
styleUrls: ['./post.page.scss'],
})
export class PostPage implements OnInit {
loadedPost: any;
constructor(private activatedRoute: ActivatedRoute, private postService: PostService) { }
ngOnInit() {
const postId = this.activatedRoute.snapshot.paramMap.get('postId');
this.postService.getPost(postId).subscribe(result => {
console.log('details: ', result);
this.loadedPost = result;
});
}
}
帖子.page.html
<ion-card-header>
<ion-card-title text-center>{{loadedPost.title}}</ion-card-title>
</ion-card-header>
console.log 输出
post:
author_id: 0
body: "<p>This is the body of the lorem ipsum post</p>"
category_id: null
created_at: "2019-06-13 17:08:45"
excerpt: "This is the excerpt for the Lorem Ipsum Post"
featured: 0
id: 1
image: "posts/post1.jpg"
meta_description: "This is the meta description"
meta_keywords: "keyword1, keyword2, keyword3"
seo_title: null
slug: "lorem-ipsum-post"
status: "PUBLISHED"
title: "Lorem Ipsum Post"
console.log截图:console.log 响应截图
根据console.log(result)
的图像,响应似乎是这样的:
{
"post": {
"title": "..."
}
}
所以你需要像这样分配你的loadedPost
:
// ...
this.postService.getPost(postId).subscribe((result: any) => {
console.log('post: ', result.post);
this.loadedPost = result.post; // <----- I've changed this!
});
然后像这样显示标题:
<ion-card-header>
<ion-card-title text-center>{{ loadedPost?.title }}</ion-card-title>
</ion-card-header>
请注意?
在{{ loadedPost?.title }}
是需要的,因为loadedPost
属性是由一个异步方法分配的,所以在API 返回响应之前它首先是undefined
的。
尝试这个:
<ion-card-header>
<ion-card-title text-center>{{loadedPost && loadedPost.title}}</ion-card-title>
</ion-card-header>
我有另一个 asyc 解决方案,试试这个:
在 TS
import { Component, OnInit } from '@angular/core';
import { ActivatedRoute } from '@angular/router';
import { PostService } from '../post.service';
import { Observable } from 'rxjs/Observable';
@Component({
selector: 'app-post',
templateUrl: './post.page.html',
styleUrls: ['./post.page.scss'],
})
export class PostPage implements OnInit {
loadedPost$: Observable<any>;
constructor(private activatedRoute: ActivatedRoute, private postService: PostService) { }
ngOnInit() {
const postId = this.activatedRoute.snapshot.paramMap.get('postId');
this.loadedPost$ = this.postService.getPost(postId)
}
}
在 HTML 中
<ion-card-header>
<ion-card-title text-center>{{(loadedPost$ | async)?.title}}</ion-card-title>
</ion-card-header>
根据@sebaferreras 在console.log(result)
指出的,我改为这样做;
<ion-card-header>
<ion-card-title text-center>{{loadedPost?.post.title}}</ion-card-title>
</ion-card-header>
您可能需要使用安全的导航操作在HTML文件中,就像这样{{ loadedPost?.title }}
或使用ngIf
检查loadedPost
初始化:
<ion-card-header *ngIf="loadedPost">
<ion-card-title text-center>
{{loadedPost.title}}
</ion-card-title>
</ion-card-header>
不要忘记在对象属性之前添加 Elvis 运算符 (?):
加载后? .title
当对象被异步设置时(即使用 HTTP 请求),这很有用。
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