角度2 |如何在FormControl中处理输入类型文件? [英] Angular 2 | How to handle input type file in FormControl?

问题描述

美好的一天，

我如何处理formControl中的输入类型文件?即时通讯使用反应形式，但是当我得到形式的值时，它在我的<input type="file"> ??

How can i handle input type file in formControl? im using reactive form but when i get the value of my form it returns null value on my <input type="file">??

推荐答案

您需要编写自己的FileInputValueAccessor.这是矮人和代码:

You need to write your own FileInputValueAccessor. Here is the plunker and the code:

@Directive({
  selector: 'input[type=file]',
  providers: [
    {
      provide: NG_VALUE_ACCESSOR,
      useExisting: FileValueAccessorDirective,
      multi: true
    }
  ]
})
export class FileValueAccessorDirective implements ControlValueAccessor {
  onChange;

  @HostListener('change', ['$event.target.value']) _handleInput(event) {
    this.onChange(event);
  }

  constructor(private element: ElementRef, private render: Renderer2) {  }

  writeValue(value: any) {
    const normalizedValue = value == null ? '' : value;
    this.render.setProperty(this.element.nativeElement, 'value', normalizedValue);
  }

  registerOnChange(fn) {    this.onChange = fn;  }

  registerOnTouched(fn: any) {  }

  nOnDestroy() {  }
}

然后您将能够获得如下更新:

And then you will be able to get updates like this:

@Component({
  moduleId: module.id,
  selector: 'my-app',
  template: `
      <h1>Hello {{name}}</h1>
      <h3>File path is: {{path}}</h3>
      <input type="file" [formControl]="ctrl">
  `
})
export class AppComponent {
  name = 'Angular';
  path = '';
  ctrl = new FormControl('');

  ngOnInit() {
    this.ctrl.valueChanges.subscribe((v) => {
      this.path = v;
    });
  }
}

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