实现 ControlValueAccessor 和 Validator 的 MatFormFieldControl 创建循环依赖

Question

我正在尝试通过实现 MatFormFieldControl、ControlValueAccessor 和 Validator 接口来创建自定义表单控件。

但是，当我提供 NG_VALUE_ACCESSOR 或 NG_VALIDATORS..

@Component({
  selector: 'fe-phone-number-input',
  templateUrl: './phone-number-input.component.html',
  styleUrls: ['./phone-number-input.component.scss'],
  providers: [
    {
      provide: MatFormFieldControl,
      useExisting: forwardRef(() => PhoneNumberInputComponent)
    },
    {
      provide: NG_VALUE_ACCESSOR,
      useExisting: forwardRef(() => PhoneNumberInputComponent),
      multi: true,
    },
    {
      provide: NG_VALIDATORS,
      useExisting: forwardRef(() => PhoneNumberInputComponent),
      multi: true
    }
  ]
})
export class PhoneNumberInputComponent implements MatFormFieldControl<string>,
  ControlValueAccessor, Validator, OnDestroy {
  ...
}

创建了循环依赖：

Uncaught Error: Template parse errors: Cannot instantiate cyclic dependency! NgControl

这个有效：

@Component({
  selector: 'fe-phone-number-input',
  templateUrl: './phone-number-input.component.html',
  styleUrls: ['./phone-number-input.component.scss'],
  providers: [
    {
      provide: MatFormFieldControl,
      useExisting: forwardRef(() => PhoneNumberInputComponent)
    }
  ]
})
export class PhoneNumberInputComponent implements MatFormFieldControl<string>,
  ControlValueAccessor, Validator, OnDestroy {
  ...
  constructor(@Optional() @Self() public ngControl: NgControl) {
    if (this.ngControl) {
      this.ngControl.valueAccessor = this;
    }
  }
}

但我仍然不知道如何进行验证。提供 NG_VALIDATORS 会产生循环依赖。如果不提供它，validate 方法就不会被调用。

我正在使用@angular/material 5.0.4.

Answer 1

为了摆脱循环依赖，我从组件中删除了 Validator 接口，而是直接提供了验证器函数。

export function phoneNumberValidator(control: AbstractControl) {
  ...
}

@Component({
  selector: 'fe-phone-number-input',
  templateUrl: './phone-number-input.component.html',
  styleUrls: ['./phone-number-input.component.scss'],
  providers: [
    {
      provide: MatFormFieldControl,
      useExisting: forwardRef(() => PhoneNumberInputComponent)
    },
    {
      provide: NG_VALIDATORS,
      useValue: phoneNumberValidator,
      multi: true
    }
  ]
})
export class PhoneNumberInputComponent implements MatFormFieldControl<string>,
  ControlValueAccessor, OnDestroy {
  ...
  constructor(@Optional() @Self() public ngControl: NgControl) {
    if (this.ngControl) {
      this.ngControl.valueAccessor = this;
    }
  }
}

Answer 2

一个干净的做法是使用与 @Component 相同的选择器创建一个 @Directive。这种方式使 @Directive 能够镜像 @Component 拥有的任何 @Input 并在验证时考虑到它。

@Directive({
  selector: 'fe-phone-number-input',
  providers: [
    {
      provide: NG_VALIDATORS,
      useExisting: PhoneNumberInputValidatorDirective,
      multi: true
    }
  ]
})
export class PhoneNumberInputValidatorDirective implements Validator { ... }

Answer 3

我的解决方案采用了@blid 的想法，而是复制与正在验证的组件相同的 @Inputs，我通过依赖注入注入组件，如下所示：

@Directive({
  selector: 'fe-phone-number-input, [fePhoneNumber]',
  providers: [
    {
      provide: NG_VALIDATORS,
      useExisting: PhoneNumberInputValidatorDirective,
      multi: true
    }
  ]
})
export class PhoneNumberInputValidatorDirective implements Validator {
  constructor(private injector: Injector) {}
  
  validate(control: FormControl) {
    // use @Self to get the only instance of component that this validator is directly attached to
    // use @Optional so that this validator can be used separately as a directive via attribute `fePhoneNumber`
    const phoneNumberInputComponent = this.injector.get(PhoneNumberInputComponent, undefined, InjectFlags.Self | InjectFlags.Optional);

    if (phoneNumberInputComponent?.myInput) {
      // some custom logic
    }
    return null;
  }
}

Answer 4

我不确定您是否需要实现 validator 接口。对于我的自定义控件，我使用注入的 ngControl 进行任何验证。

@Component({
  selector: 'fe-phone-number-input',
  templateUrl: './phone-number-input.component.html',
  styleUrls: ['./phone-number-input.component.scss'],
  providers: [
    {
      provide: MatFormFieldControl,
      useExisting: forwardRef(() => PhoneNumberInputComponent),
    },
  ],
})
export class PhoneNumberInputComponent
  implements MatFormFieldControl<string>, ControlValueAccessor
{

  constructor(@Optional() @Self() public ngControl: NgControl) {
    if (this.ngControl != null) {
      this.ngControl.valueAccessor = this;
    }
  }

  updatePhone(phone: string) {
    this.value = phone;
    this.ngControl.control?.updateValueAndValidity();
  } 
}

<input
  class="phone-number-input mat-input-element"
  type="text"
  (blur)="updateValue(phoneInput.value)"
  [required]="required"
  #phoneInput
/>

实现 ControlValueAccessor 和 Validator 的 MatFormFieldControl 创建循环依赖

MatFormFieldControl that implements ControlValueAccessor and Validator creates cyclic dependency

typescript

angular-material

angular-components

angular

angular5