javascript - 在 MEAN CRUD 应用程序中确认删除后无法读取未定义的属性 '_id'？

Question

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这是我用来学习 MEAN CRUD 操作的教程的链接。

根据要求，我在下面发布相关代码。 Chrome 控制台还显示 TypeError: Cannot read property '_id' of undefined 在 todo-list.component.ts:56。

tod​​olist.component.ts

import { Component, OnInit } from '@angular/core';
import { TodoService } from '../todo.service';
@Component({
  selector: 'app-todo-list',
  templateUrl: './todo-list.component.html',
  styleUrls: ['./todo-list.component.css']
})
export class TodoListComponent implements OnInit {
  todos:any[] = [];
  todo:any = {};
  todoToEdit:any = {};
  todoToDelete:any = {};
  apiMessage:string;
constructor(private todoService:TodoService) { }
ngOnInit(): void {
    this.todoService.showAddTodoBox = true;
    this.todoService.getTodos()
                    .then(td => this.todos = td.todos )
  }
AddTodo(todo:any):void{
    if(!todo){ return; }
    this.todoService.createTodo(todo)
                    .then(td => {
                      console.log(td);
                      this.todos.push(td.todo);
                    })
  }
showEditTodo(todo:any):void{
    this.todoToEdit = todo;
    this.apiMessage = "";
  }
EditTodo(todo:any):void{
    if(!todo){ return; }
    todo.id = this.todoToEdit._id;
    this.todoService.updateTodo(todo)
                    .then(td => {
                      const updatedTodos = this.todos.map(t => {
                        if(td.todo._id !== t._id){
                          return t;
                        }
                        return { ...t, ...td.todo };
                      })
                      this.apiMessage = td.message;
                      this.todos = updatedTodos;
                    })
  }
showDeleteTodo(todo:any):void{
   this.todoToDelete = todo;
   this.apiMessage = "";
 }
DeleteTodo(todo:any):void{
   if(!todo){ return; }
   this.todoService.deleteTodo(todo)
                   .then(td => {
                     const filteredTodos = this.todos.filter(t => t._id !== td.todo._id);
                     this.apiMessage = td.message;
                     this.todos = filteredTodos;
                   })
 }
}

这里是 todo-list.component.html

    <div align="center" class="AddTodoBox" [hidden]="todoService.showAddTodoBox">
  <h4>Add New Todo</h4>
  <form (ngSubmit)="AddTodo(todo);todoForm.reset()" #todoForm="ngForm">
  <div class="form-group">
    <label for="todoText">Todo:</label>
    <input type="text" [(ngModel)]="todo.todoText" #todotext="ngModel" class="form-control" name="todoText" id="todoText" required />
    <div [hidden]="todotext.valid || todotext.pristine"
         class="alert alert-danger">
      Todo is required
    </div>
  </div>
  <div class="form-group">
    <label for="todoDesc">Description:</label>
    <input type="text" class="form-control" [(ngModel)]="todo.todoDesc" #tododesc="ngModel" name="todoDesc" id="todoDesc" required />
    <div [hidden]="tododesc.valid || tododesc.pristine"
         class="alert alert-danger">
      Description is required
    </div>
  </div>
<button type="submit" [disabled]="!todoForm.form.valid" class="btn btn-success btn-block">Submit</button>
</form>
</div>
<div *ngIf="todos && todos.length > 0" class="TodoListBox">
  <h2 align="center">Your Todo's List</h2>
  <table id="mytable" class="table table-bordred table-striped">
<thead>
                    <th>Todo</th>
                      <th>View</th>
                       <th>Edit</th>
                      <th>Delete</th>
                    </thead>
     <tbody>
<tr *ngFor="let todo of todos">
     <td>{{todo.todoText}}</td>
     <td><a  [routerLink]="['/todo', todo._id]" title="Click to Open {{todo.todoText}}">View</a></td>
     <td><p data-placement="top" data-toggle="tooltip" title="Edit"><button class="btn btn-primary btn-xs" (click) = "showEditTodo(todo)" data-title="Edit" data-toggle="modal" data-target="#edit" ><span class="glyphicon glyphicon-pencil"></span></button></p></td>
     <td><p data-placement="top" data-toggle="tooltip" title="Delete"><button class="btn btn-danger btn-xs" (click) = "showDeleteTodo(todo)" data-title="Delete" data-toggle="modal" data-target="#delete" ><span class="glyphicon glyphicon-trash"></span></button></p></td>
     </tr>
<tr>
  </tbody>
  </table>
  <!-- Edit Modal -->
  <div class="modal fade" id="edit" role="dialog">
    <div class="modal-dialog modal-md">
      <div class="modal-content">
        <div class="modal-header">
          <button type="button" class="close" data-dismiss="modal">&times;</button>
          <h4 class="modal-title">Edit Todo</h4>
        </div>
        <div class="modal-body">
          <div align="center" class="EditTodoBox">
            <form (ngSubmit)="EditTodo(todoToEdit)" #editTodoForm="ngForm">
            <div class="form-group">
              <label for="todoText">Todo:</label>
              <input type="text" [(ngModel)]="todoToEdit.todoText" #todoedittext="ngModel" class="form-control" name="todoText" id="todoText" required />
              <div [hidden]="todoedittext.valid || todoedittext.pristine"
                   class="alert alert-danger">
                Todo is required
              </div>
            </div>
            <div class="form-group">
              <label for="todoDesc">Description:</label>
              <textarea class="form-control" [(ngModel)]="todoToEdit.todoDesc" #todoeditdesc="ngModel" name="todoDesc" id="todoDesc" required></textarea>
              <div [hidden]="todoeditdesc.valid || todoeditdesc.pristine"
                   class="alert alert-danger">
                Description is required
              </div>
            </div>
<button type="submit" [disabled]="!editTodoForm.form.valid || !editTodoForm.form.dirty" class="btn btn-success btn-block">Submit</button>
          </form>
          <div style="margin:10px;" *ngIf="apiMessage" align="center" class="alert alert-success" role="alert">
          <strong>{{apiMessage}}</strong>
          </div>
          </div>
        </div>
        <div class="modal-footer">
          <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
        </div>
      </div>
    </div>
  </div>
<!-- Delete Modal -->
  <div class="modal fade" id="delete" role="dialog">
    <div class="modal-dialog modal-md">
      <div class="modal-content">
        <div class="modal-header">
          <button type="button" class="close" data-dismiss="modal">&times;</button>
          <h4 class="modal-title">Delete Todo</h4>
        </div>
        <div class="modal-body">
          <div align="center" class="DeleteTodoBox">
            <div *ngIf="!apiMessage" align="center" class="alert alert-danger" role="alert">
              <p>Are you sure want to delete this todo?</p>
            <strong>{{todoToDelete.todoText}}</strong>
            </div>
          <div style="margin:10px;" *ngIf="apiMessage" align="center" class="alert alert-success" role="alert">
          <strong>{{todoToDelete.todoText}}</strong>  {{apiMessage}}
          </div>
          </div>
        </div>
        <div class="modal-footer">
          <button type="button" class="btn btn-danger" *ngIf="!apiMessage" (click)="DeleteTodo(todoToDelete)">Confirm</button>
          <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
        </div>
      </div>
    </div>
  </div>
</div>
<div *ngIf="todos.length <= 0" class="NoTodosBox">
<div align="center" class="alert alert-info" role="alert">
<strong>No Todos Available in Database</strong>
</div>
</div>

Answer 1

如评论中所述；您可以使用要删除的待办事项来解决它。可通过 closure 获得.

您可以查看 todoService.deleteTodo 解析的内容，并查看已删除待办事项的 ID 是否可用。

要在闭包中使用已删除的待办事项的 ID，您可以这样做:

const filteredTodos = this.todos.filter(t => t._id !== todo._id)