未定义标识符“必需”。 '__type' 不包含这样的成员

Question

我需要声明这个变量来输入任何类型吗？这显示在我的 HTML 模板的可视化代码编辑器中。

product-form.component.html

<div class="row">

  <div class="col-md-6">
      <form #form="ngForm" (ngSubmit)="save(form.value)">

            <div class="form-group">
              <label for="title">Title</label>
              <input #title="ngModel" [(ngModel)]="product.title" name="title" id="title" type="text" class="form-control" required>
              <div class="alert alert-danger" *ngIf="title.touched && title.invalid">
                Title is required.
              </div>
            </div>

            <div class="form-group">
                <label for="price">Price</label>
                <div class="input-group">
                  <span class="input-group-addon">$</span>
                  <input #price="ngModel" ngModel [(ngModel)]="product.price" name="price" id="price" type="number" class="form-control" required [min]="0">
                </div>
                <div class="alert alert-danger" *ngIf="price.touched && price.invalid">
                  <div *ngIf="price.errors.required">Price is required.</div>
                  <div *ngIf="price.errors.min">Price should be 0 or higher.</div>
                </div>
            </div>

            <div class="form-group">
                <label for="category">Category</label>
                <select #category="ngModel" ngModel [(ngModel)]="product.category" name="category" id="category" class="form-control" required>
                  <option value=""></option>
                  <option *ngFor="let category of categories$ | async" [value]="category.key">{{ category.payload.val().name }}</option>
                </select>
                <div class="alert alert-danger" *ngIf="category.touched && category.invalid">
                  Category is required.
                </div>
            </div>

            <div class="form-group">
                <label for="imageUrl">Image URL</label>
                <input #imageUrl="ngModel" ngModel [(ngModel)]="product.imageUrl" name="imageUrl" id="imageUrl" type="text" class="form-control" required url>
                <div class="alert alert-danger" *ngIf="imageUrl.touched && imageUrl.invalid">
                  <div *ngIf="imageUrl.errors.required">Image URL is required.</div>
                  <div *ngIf="imageUrl.errors.url">Please enter a valid URL.</div>
                </div>
            </div>

            <button class="btn btn-primary">Save</button>

          </form>
  </div>

  <div class="col-md-6">
      <div class="card" style="width: 20rem;">
          <img class="card-img-top" [src]="product.imageUrl" *ngIf="product.imageUrl">
          <div class="card-block">
            <h4 class="card-title">{{ product.title }}</h4>
            <p class="card-text">{{ product.price | currency: 'USD': symbol }}</p>
          </div>
        </div>
  </div>

</div>

product-form.component.ts

import { Component, OnInit } from '@angular/core';
import { CategoryService } from '../../category.service';
import { ProductService } from '../../product.service';
import { Router } from '@angular/router';
import { ActivatedRoute } from '@angular/router';
import 'rxjs/add/operator/take';

@Component({
  selector: 'app-product-form',
  templateUrl: './product-form.component.html',
  styleUrls: ['./product-form.component.css']
})
export class ProductFormComponent implements OnInit {

  categories$;
  product: any = {};

  constructor(
    private router: Router,
    private route: ActivatedRoute,
    private categoryService: CategoryService,
    private productService: ProductService) {
    this.categories$ = categoryService.getCategories();

    let id = this.route.snapshot.paramMap.get('id');
    if (id) {
      this.productService.get(id).take(1).subscribe(p => this.product = p);
    }
  }

  save(product) {
    this.productService.create(product);
    this.router.navigate(['/admin/products']);
  }

  ngOnInit() {
  }

}

如何消除此错误？应用程序中的功能似乎没有受到影响。因此，据我了解，它会编译成有效的 JS。我能够通过将对象声明为“任何”来修复对象

如果可能的话，我有兴趣学习如何为此设置界面。

Answer 1

角度有一个错误。如果您像这样编写 *ngIf，该编译器错误将消失：

          <div *ngIf="price.errors['required']">

Answer 2

尝试添加“？”在“价格”之后。

像这样：

<div *ngIf="price?.errors.required">Price is required.</div>
<div *ngIf="price?.errors.min">Price should be 0 or higher.</div>

Answer 3

我的 VS Code 也有同样的问题。我只在条件之前使用!! 解决了它。

试试：

<div *ngIf="!!price.errors.required">Price is required.</div>
<div *ngIf="!!price.errors.min">Price should be 0 or higher.</div>

更多信息：https://github.com/angular/vscode-ng-language-service/issues/126

Answer 4

<div class="alert alert-danger" *ngIf="email.touched && !email.valid">
     <div *ngIf="email.errors['required']">Email is required</div>
     <div *ngIf="email.errors['minlength']">Email should be minimum {{ email.errors['minlength']['requiredLength'] }} characters</div>
     <div *ngIf="email.errors['maxlength']">Email should be maximum {{ email.errors['maxlength']['requiredLength'] }} characters</div>
     <div *ngIf="email.errors['pattern']">Email doesn't match the pattern.</div>
</div>

Answer 5

尝试使用ngFor 访问视图上的FormGroup 内的FormArray 控件时遇到类似错误。

此问题的某些答案部分起作用，导致编译错误或项目构建失败。例如：

libraryForm.get('books') //compile error
libraryForm.controls['books'].controls' //build failure

到目前为止，只有以下解决方案对我有用：

libraryForm['controls']['books']['controls']

整个元素：

<div [formGroupName]="i" *ngFor="let book of libraryForm['controls']['books']['controls'];let i = index">

Answer 6

使用hasError() 方法而不是errors 属性可以为我修复它。
像这样使用它：

 <div *ngIf="price.hasError('required')">Price is required.</div>

Answer 7

您可以在您的财产前面添加问号

  <label [attr.data-error]="Password.errors!=null?(Password?.errors.Required?'Required 
  field!':'Minimum 3 Characters Needed'):''">Password</label>

Answer 8

我遇到了同样的问题，感谢 António César Júnior 的回答，您解决了：

https://stackoverflow.com/a/53403416/8992452 仅使用

   !!

<div *ngIf="submitted && f.username.errors">
    <p *ngIf="f.username.errors.required">Email is required</p>
    <p *ngIf="f.username.errors.email">The mail address is invalid</p>
</div>

在以前的项目中工作，然后更改为：

 <div *ngIf="submitted && !!f.username.errors">
   <p *ngIf="!!f.username.errors.required">Email is required</p>
   <p *ngIf="!!f.username.errors.email">The mail address is invalid</p>
 </div>

Answer 9

请检查此解决方案（对我来说效果很好）！

<div class="alert alert-danger" *ngIf="username.touched && username.invalid">
  <div *ngIf="username.errors['required']">Username are required!</div>
  <div *ngIf="username.errors['minlength']">Username should be minimum {{ username.errors['minlength'].requiredLength }} characters!</div>
  <div *ngIf="username.errors['cannotContainSpace']">Username cannot contains spaces!</div>
</div>

Answer 10

docs 中似乎确实提到了一些问题：

有时绑定表达式会在 AOT 编译期间触发类型错误，并且不可能或难以完全指定类型。要消除错误，您可以使用 $any() 转换函数将表达式转换为任何类型，如下例所示

所以你可以这样做：

$any(price.errors).required