node.js - TypeError:无法读取Angular4中未定义的属性“_id”

我已经为CRUD功能开发了一个简单的均值堆栈应用程序。现在我的后端可以正常工作，即将数据发布到MongoDB，但是前端似乎给我一个问题：

    ERROR Type Error: Cannot read property '_id' of undefined
        at Object.eval [as updateDirectives] (EmployeeComponent.html:4)
        at Object.debugUpdateDirectives [as updateDirectives] (core.js:10846)
        at checkAndUpdateView (core.js:10243)
        at callViewAction (core.js:10484)
        at execComponentViewsAction (core.js:10426)
        at checkAndUpdateView (core.js:10249)
        at callViewAction (core.js:10484)
        at execComponentViewsAction (core.js:10426)
        at checkAndUpdateView (core.js:10249)
        at callWithDebugContext (core.js:11136)

在以下位置遇到此错误：

  <form #employeeForm="ngForm" (ngSubmit)="onSubmit(employeeForm)">
    <input type="hidden" name="_id" #_id="ngModel" [(ngModel)]="employeeService.selectedEmployee._id">
    <div class="row">
      <div class="input-field col s12">
        <input type="text" name="name" #name="ngModel" [(ngModel)]="employeeService.selectedEmployee.name">
        <label>Name :
          <label class="red-text">*</label>
        </label>

最佳答案

由于您是从api异步检索数据，因此请使用* ngIf处理空数据，如下所示，

 <form *ngIf="employeeService?.selectedEmployee?" #employeeForm="ngForm" (ngSubmit)="onSubmit(employeeForm)">
    <input type="hidden" name="_id" #_id="ngModel" [(ngModel)]="employeeService.selectedEmployee._id">
    <div class="row">
      <div class="input-field col s12">
        <input type="text" name="name" #name="ngModel" [(ngModel)]="employeeService.selectedEmployee.name">
        <label>Name :
          <label class="red-text">*</label>
        </label>

关于node.js - TypeError:无法读取Angular4中未定义的属性“_id”，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/51344790/