EXCEPTION: Uncaught (in promise): TypeError: Cannot read property 'touched' of null

Question

我正在尝试在我的 Angular2 应用程序中使用 Reactive 表单，但我运行出现如下异常

EXCEPTION: Uncaught (in promise): TypeError: Cannot read property 'touched' of null TypeError: Cannot read property 'touched' of null

我的示例代码如下

import { Component, OnInit } from '@angular/core';
import { NgForm } from '@angular/forms';
import {FormGroup, FormControl} from '@angular/forms';
import { Customer } from './customer';

@Component({
moduleId:module.id,
templateUrl: 'sign-up.reactiveForms.html'
})

export class SignupComponent  {

customer: Customer= new Customer();


customerForm : FormGroup; //it assosciate html element with this root model

ngOnInit() : void {


   this.customerForm=new FormGroup({

        firstName: new FormControl(),
         lastName: new FormControl(),
         email: new FormControl(),
         sendCatalog: new FormControl(true)

   });
}

save() {
    console.log(this.customerForm);
  }

}

sign-up.reactiveForms.html文件如下

            <!-- First Name input -->

            <div class="form-group"
                [ngClass]="{'has-error': (customerForm.get('firstName').touched ||customerForm.get('firstName').dirty) && !customerForm.get('firstName').valid }">
                <label class="col-md-2 control-label" 
                       for="firstNameId">First Name</label>

                <div class="col-md-8">
                    <input class="form-control" 
                           id="firstNameId" 
                           type="text" 
                           placeholder="First Name (required)" 
                           required 
                           minlength="3"
                           formControlName="firstName"
                             />
                    <span class="help-block" *ngIf="(customerForm.get('firstName').touched || customerForm.get('firstName').dirty) && customerForm.get('firstName').errors">
                        <span *ngIf="customerForm.get('firstName').errors.required">
                            Please enter your first name.
                        </span>
                        <span *ngIf="customerForm.get('firstName').errors.minlength">
                            The first name must be longer than 3 characters.
                        </span>
                    </span>
                </div>
            </div>

我想弄明白为什么 touched 属性是空的。

Answer 1

尝试并初始化您的表单控件，这样它们就不会 null:

this.customerForm=new FormGroup({
    firstName: new FormControl(''),
    lastName: new FormControl(''),
    email: new FormControl(''),
    sendCatalog: new FormControl(true)
});

否则使用安全导航运算符可能会消除空错误，例如：

customerForm.get('firstName')?.touched

但是单独初始化表单控件应该（希望）解决这个问题。

EXCEPTION: Uncaught (in promise): TypeError: Cannot read property 'touched' of null

EXCEPTION: Uncaught (in promise): TypeError: Cannot read property 'touched' of null

angular

angular-reactive-forms