小编abd*_*rpi的帖子

请问你能告诉我如何解决这个问题吗？

浏览器中的问题：

core.js:6479 ERROR TypeError: Cannot read properties of undefined (reading 'title')
    at BookItemComponent_Template (book-item.component.html:4)
    at executeTemplate (core.js:9599)
    at refreshView (core.js:9465)
    at refreshComponent (core.js:10636)
    at refreshChildComponents (core.js:9261)
    at refreshView (core.js:9515)
    at refreshComponent (core.js:10636)
    at refreshChildComponents (core.js:9261)
    at refreshView (core.js:9515)
    at renderComponentOrTemplate (core.js:9579)

图书.服务.ts：

import { Injectable } from '@angular/core';
    import { Book } from './book.model';
    import { HttpClient} from '@angular/common/http';
    
    @Injectable({
      providedIn: 'root'
    })
    export class BookService {
    
      url:string="http://localhost:31451/api/books"
      
      books:Book[];
      book:Book;
     
      constructor(private http:HttpClient) { }
      getAllbooks (){
        this.http.get(this.url).toPromise().then(
          res=>{
            this.books …