访问自定义表单控件的有效值

问题描述

我创建了代表密码表单控制的自定义组件(以下代码已简化).

I created custom component representing password form control (code below is simplified).

PasswordComponent(html)

PasswordComponent (html)

<form [formGroup]="passwordForm">
  ...
  <input formControlName="password" type="password">
</form>

PasswordComponent(ts)

PasswordComponent (ts)

...
@Component({
  selector: 'password',
  templateUrl: './password.component.html',
  styleUrls: ['./password.component.css'],
  providers: [{
    provide: NG_VALUE_ACCESSOR,
    useExisting: forwardRef(() => PasswordComponent),
    multi: true
  }]
})
export class PasswordComponent implements ControlValueAccessor {

  passwordForm: FormGroup;
  onChange = (password: string) => { };
  onTouched = () => { };

  constructor() {
    this.passwordForm = new FormGroup({
      ...
      password: new FormControl('')
    });

    this.passwordForm.valueChanges.subscribe(data => this.onChange(this.value));
  }

  get value(): string {
    return this.passwordForm.get('password').value;
  }

  writeValue(password: string): void {
    this.passwordForm.get('password').setValue(password);
    this.onChange(this.value);
  }

  registerOnChange(fn: any): void { this.onChange = fn; }

  registerOnTouched(fn: any): void { this.onTouched = fn; }

  setDisabledState?(isDisabled: boolean): void { }
}

我在其他组件而不是标准输入元素中使用它:

I use it in other components instead of standard input element:

<form [formGroup]="userForm">
  ...
  <password formControlName="password"></password>
</form>

验证者来自外部形式(它们未在PasswordComponent中定义)

Validators are coming from outer form (they're not defined inside PasswordComponent)

this.userForm = fb.group({
  ...
  password: ['', [Validators.minLength(10), Validators.maxLength(100)]]
});

我的问题是:如何从PasswordComponent内部获取<password>元素的有效性?我想根据有效性对其进行样式化.换句话说，如何从代表该控件的PasswordComponent中获得userForm的密码"控件的有效性.

My question is: how can I get <password> element validity from inside PasswordComponent? I would like to stylize it based on validity. In other words how can I get validity of userForm's 'password' control from PasswordComponent that represents this control.

推荐答案

由于我们将直接得到DI的依赖，因此无法直接从DI系统获取NgControl实例.下图显示了为什么在自定义值访问器中注入NgControl时会发生这种情况:

As we can't get NgControl instance directly from DI system since we'll get a circular dependency error. The following diagram shows why it happens if we inject NgControl in our custom value accessor:

现在应该很清楚，我们有NgControl -> FormControlName -> ValueAccessor -> CustomValueAccessor -> NgControl循环依赖项

Now it should be clear that we have NgControl -> FormControlName -> ValueAccessor -> CustomValueAccessor -> NgControl circular dependency

要解决此问题，您可以利用Injector来实现:

To work around it you can leverageInjector to achieve that:

component.ts

import { NgControl } from '@angular/forms';
export class PasswordComponent implements ControlValueAccessor {
  ...
  ngControl: NgControl;

  constructor(private inj: Injector) {
    ...
  }

  ngOnInit() {
    this.ngControl = this.inj.get(NgControl)
  }

template.html

{{ ngControl.control.valid }}

柱塞示例

Plunker Example

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