Angular 7 : How to re-validate control when a property of the model changes

Question

我有一个模板驱动的表单，它有一个输入控件，我需要使用自定义验证器来验证我模型中的属性值(根据下拉列表中的选择动态更改)。每当我在输入控件中键入时它都可以正常工作，但我希望在属性值更改时也进行验证(而不必更改输入框中的值)。有办法实现吗？？

下面是模型、标记和我正在使用的验证器的简化版本

型号:

 amountToInvest: number = null;
 public onAccountSelectionChanged(event): void {     
    // find the account based on the selection from this drop down list
    this.availableFunds = account.AvailableFunds;
  }

标记

<form name="form" (ngSubmit)="myForm.form.valid && onSubmit()" >
    <input type="number" [(ngModel)]="amountToInvest"' [customMax]="availableFunds">

验证器

@Directive({
  selector: '[customMax][formControlName],[customMax][formControl],[customMax][ngModel]',
  providers: [{provide: NG_VALIDATORS, useExisting: CustomMaxDirective, multi: true}]
})
export class CustomMaxDirective implements Validator {
  @Input()
  customMax: number;

  validate(c: FormControl): {[key: string]: any} {
      let v = c.value;
      return ( v > this.customMax)? {"customMax": true} : null;
  }

Answer 1

我所做的是手动发送一个事件

   const event = new Event('change', { bubbles: true, cancelable: false }); //Create an event
   let siblingInput = ele.parentNode['previousElementSibling']['firstChild'] as HTMLInputElement; //Get the element
   siblingInput.dispatchEvent(event); //Dispatch event

这将使控件重新生效