Form Builder with hasError() for validation throws an error of ERROR TypeError: Cannot read property 'hasError' of undefined

Question

您好，我正在使用 Form Builder

在 angular 2 中实现一个表单

在 component.ts 我已经使用 formGroup

实现了我的表单

下面是我的代码

public myForm: FormGroup;

constructor(private authenticateservice: AuthenticateService,
              private _fb: FormBuilder
             ) {


}

ngOnInit() {

this.myForm = this._fb.group({
      address: [this.userDetails.address, [<any>Validators.required]],
      address2: ['', [<any>Validators.required]],
      city: ['', [<any>Validators.required]],
      company_address: ['', [<any>Validators.required]],
      company_address2: ['', [<any>Validators.required]],
      company_city: ['', [<any>Validators.required]],
      company_country: ['', [<any>Validators.required]],
      company: ['', [<any>Validators.required , Validators.minLength(3)] ],
      company_tax_number: ['', [<any>Validators.required]],
      company_zip: ['', [<any>Validators.required,  Validators.minLength(5) , Validators.maxLength(7)]],
      country: ['', [<any>Validators.required]],
      email: ['', [<any>Validators.required, Validators.email]],
      first_name: [this.userDetails.first_name, [<any>Validators.required]],
      id: ['', [<any>Validators.required]],
      last_name: ['', [<any>Validators.required]],
      phone: ['', [<any>Validators.required, Validators.minLength(10)]],
      zip: ['', [<any>Validators.required , Validators.minLength(5) , Validators.maxLength(7)]],
      user_type: ['2', [<any>Validators.required]],
      terms: [0, [<any>Validators.required]],
      hash_tag: [''],

    });

}

它工作正常。但是在前端显示验证时

我是这样用的

  <div class="form-group row">
    <div class="col-lg-8">
      <label>Address 2</label>
      <textarea class="form-control" placeholder="Address" rows="2" [readonly]="disabled" id="companyaddress2" formControlName="company_address2"></textarea>
      <span class="help-block form-error text-danger small" *ngIf="myForm.controls['company_address2'].hasError('required')">Company Address 2 is Required.</span>
    </div>
  </div>

它正在工作，但在控制台中抛出如下错误

错误类型错误：无法读取未定义的属性'hasError'

请帮我解决这个问题。

谢谢。

Answer 1

你应该这样使用它：

<span class="help-block form-error text-danger small" 
  *ngIf="myForm.controls['company_address2'].errors?.required &&
  myForm.controls['company_address2'].touched">Company Address 2 is Required </span>

Answer 2

我在 angular 中遇到过这个问题 5 试试下面的方法你会得到输出

<mat-error>
<span class="help-block form-error text-danger small" 
  *ngIf="myForm.controls['company_address2'].errors?.required &&
  myForm.controls['company_address2'].touched">Company Address 2 is Required </span>
</mat-error>

Answer 3

我是这样解决的：

<span class="help-block form-error text-danger small" 
*ngIf="myForm.controls.company_address2.errors?.required &&
myForm.controls.company_address2.touched">
Company Address 2 is Required </span>

Answer 4

如果您正在使用响应式表单，您应该可能使用 TypeScript getter 来解决这个问题，它更简洁：

In a reactive form, you can always access any form control through the get method on its parent group, but sometimes it's useful to define getters as shorthands for the template.

A getter 将允许您直接访问表单字段，避免在上面的示例中将 myForm.controls['fieldNameGoesHere']. 与 ngIf 冗余使用。

例如，对于 company_address2，在 ngOnInit() 方法后添加以下内容：

get company_address2() { return this.myForm.get( 'company_address2' ); }

这将使您的组件 HTML 直接访问 company_address2 ，试试这个：

<textarea class="form-control" placeholder="Address" rows="2" [readonly]="disabled" id="companyaddress2" 
    formControlName="company_address2">
</textarea>

<span class="help-block form-error text-danger small"
    *ngIf="company_address2.hasError('required')">
    Company Address 2 is Required.
</span>

不过，您将单独定义每个 getter 方法，TypeScript 不允许向 getter 提供变量，因此您最终会为每个方法使用一个 get 方法在您的表单中进行控制。

可以在 Form Validation: Built-in Validators 下的 Angular 文档中找到更多信息。

Answer 5

对于所需的错误消息，这一行应该有效

 <mat-error>Title is required</mat-error>

Form Builder with hasError() for validation throws an error of ERROR TypeError: Cannot read property 'hasError' of undefined

Form Builder with hasError() for validation throws an error of ERROR TypeError: Cannot read property 'hasError' of undefined

angular

angular2-formbuilder

angular-reactive-forms

angular-validation

angular-forms