Angular2 -使用旧数据的自定义验证器

import { AbstractControl, ValidatorFn } from '@angular/forms';

export function customValidator(oldData: any): ValidatorFn {
  return (control: AbstractControl): { [key: string]: any } | null => {
    const currentValue = control.value;
    
    // 使用旧数据进行比较和验证
    if (currentValue !== oldData) {
      return { 'customValidation': true };
    }
    
    return null;
  };
}

import { Component } from '@angular/core';
import { FormControl, FormGroup, Validators } from '@angular/forms';
import { customValidator } from './custom-validator';

@Component({
  selector: 'app',
  template: `
    <form [formGroup]="myForm">
      <input type="text" formControlName="myControl">
      <div *ngIf="myForm.get('myControl').hasError('customValidation')">验证失败</div>
    </form>
  `,
})
export class AppComponent {
  myForm: FormGroup;
  
  constructor() {
    this.myForm = new FormGroup({
      myControl: new FormControl('', [
        Validators.required,
        customValidator('旧数据')
      ])
    });
  }
}