File upload from <input type="file">

Using angular 2 beta, I cannot seem to get an <input type="file"> to work.

Using diagnostic, I can see two-way binding for other types such as text.

<form>
    {{diagnostic}}
    <div class="form-group">
        <label for="fileupload">Upload</label>
        <input type="file" class="form-control" [(ngModel)]="model.fileupload">
    </div>
</form>

In my TypeScript file, I have the following diagnostic line:

get diagnostic() { return JSON.stringify(this.model); }

Could it be that it is the issue of not being JSON? The value is null.

I cannot really verify the value of the input. Уven though the text next to "Choose file ..." updates, I cannot see differences in the DOM for some reason.

Solution 1:

I think that it's not supported. If you have a look at this DefaultValueAccessor directive (see https://github.com/angular/angular/blob/master/modules/angular2/src/common/forms/directives/default_value_accessor.ts#L23). You will see that the value used to update the bound element is $event.target.value.

This doesn't apply in the case of inputs with type file since the file object can be reached $event.srcElement.files instead.

For more details, you can have a look at this plunkr: https://plnkr.co/edit/ozZqbxIorjQW15BrDFrg?p=info:

@Component({
  selector: 'my-app',
  template: `
    <div>
      <input type="file" (change)="onChange($event)"/>
    </div>
  `,
  providers: [ UploadService ]
})
export class AppComponent {
  onChange(event) {
    var files = event.srcElement.files;
    console.log(files);
  }
}

Solution 2:

@Component({
  selector: 'my-app',
  template: `
    <div>
      <input name="file" type="file" (change)="onChange($event)"/>
    </div>
  `,
  providers: [ UploadService ]
})
export class AppComponent {
  file: File;
  onChange(event: EventTarget) {
        let eventObj: MSInputMethodContext = <MSInputMethodContext> event;
        let target: HTMLInputElement = <HTMLInputElement> eventObj.target;
        let files: FileList = target.files;
        this.file = files[0];
        console.log(this.file);
    }

   doAnythingWithFile() {
   }

}

Solution 3:

There is a slightly better way to access attached files. You could use template reference variable to get an instance of the input element.

Here is an example based on the first answer:

@Component({
  selector: 'my-app',
  template: `
    <div>
      <input type="file" #file (change)="onChange(file.files)"/>
    </div>
  `,
  providers: [ UploadService ]
})

export class AppComponent {
  onChange(files) {
    console.log(files);
  }
}

Here is an example app to demonstrate this in action.

Template reference variables might be useful, e.g. you could access them via @ViewChild directly in the controller.

Solution 4:

Another way using template reference variable and ViewChild, as proposed by Frelseren:

import { ViewChild } from '@angular/core';

@Component({
  selector: 'my-app',
  template: `
    <div>
      <input type="file" #fileInput/>
    </div>
  `
})  
export class AppComponent {
  @ViewChild("fileInput") fileInputVariable: any;
  randomMethod() {
    const files = this.fileInputVariable.nativeElement.files;
    console.log(files);
  }
}

Also see https://stackoverflow.com/a/40165524/4361955

Solution 5:

Try this small lib, works with Angular 5.0.0

• https://www.npmjs.com/package/ng2-file-upload

Quickstart example with ng2-file-upload 1.3.0:

User clicks custom button, which triggers upload dialog from hidden input type="file" , uploading started automatically after selecting single file.

app.module.ts:

import {FileUploadModule} from "ng2-file-upload";

your.component.html:

...
  <button mat-button onclick="document.getElementById('myFileInputField').click()" >
    Select and upload file
  </button>
  <input type="file" id="myFileInputField" ng2FileSelect [uploader]="uploader" style="display:none">
...

your.component.ts:

import {FileUploader} from 'ng2-file-upload';
...    
uploader: FileUploader;
...
constructor() {
   this.uploader = new FileUploader({url: "/your-api/some-endpoint"});
   this.uploader.onErrorItem = item => {
       console.error("Failed to upload");
       this.clearUploadField();
   };
   this.uploader.onCompleteItem = (item, response) => {
       console.info("Successfully uploaded");
       this.clearUploadField();

       // (Optional) Parsing of response
       let responseObject = JSON.parse(response) as MyCustomClass;

   };

   // Asks uploader to start upload file automatically after selecting file
  this.uploader.onAfterAddingFile = fileItem => this.uploader.uploadAll();
}

private clearUploadField(): void {
    (<HTMLInputElement>window.document.getElementById('myFileInputField'))
    .value = "";
}

Alternative lib, works in Angular 4.2.4, but requires some workarounds to adopt to Angular 5.0.0

• https://www.npmjs.com/package/angular2-http-file-upload