@Output 从指令向父组件发出值 Angular 4

Question

我有一些上传指令，非常简单，唯一的问题是我必须从这个指令组件向父组件发出值。有人知道一个简单的解决方案吗？提前致谢。这是我现在的指令：

上传-field.component.ts

import { Component, OnInit, Input } from '@angular/core';
import { TooltipModule } from 'ngx-bootstrap/tooltip';

@Component({
  selector: 'app-upload-field',
  templateUrl: './upload-field.component.html',
  styleUrls: ['./upload-field.component.scss']
})
export class UploadFieldComponent implements OnInit {

  @Input() labelName: string;
  @Input() placeHolderValue: string;
  value = '';

  constructor() { }

  ngOnInit() {
  }

  uploadButton(event: any) {
    this.value += event.target.value;
    this.value = this.value.replace(/^.*\/, '');
  }

}

上传-field.component.html

<input placeholder="{{placeHolderValue}}" disabled="disabled" class="form-control first-input" value="{{value}}" />
<div class="file-upload">
  <span class="btn btn-default btn-lg">{{labelName}}</span>
  <input type="file" class="form-control upload-button" (change)="uploadButton($event)" value="{{value}}" />
</div>

我是这样使用的：

<app-upload-field [labelName]="'Blader'" [placeHolderValue]="'Kies bestand'"></app-upload-field>

Answer 1

您可以为此使用 EventEmitter。

参考：Parent listens for child event

import { Component, Output, EventEmitter } from '@angular/core';
@Component({
  //...your decorator properties
})
export class UploadFieldComponent { 
    @Output() onValueChanged = new EventEmitter<any>();

    uploadButton() {
       this.value += event.target.value;
       this.value = this.value.replace(/^.*\/, '');
       this.onValueChanged.emit(this.value);
    }

}

在父组件中，模板：

<app-upload-field [labelName]="'Blader'" [placeHolderValue]="'Kies bestand'" 
    (onValueChanged)=onValueChanged($event)>
</app-upload-field>

在组件代码中，

 onValueChanged(value) {
       // value will be the emitted value by the child
 }

The child component exposes an EventEmitter property with which it emits events when something happens. The parent binds to that event property and reacts to those events.

Answer 2

在UploadFieldComponent中

export class UploadFieldComponent implements OnInit {
...
@Output myValueChanged = new  EventEmitter<string>();//passing a string value to parent
...
  uploadButton(event: any) {
    ...
    myValueChanged.emit(valueToBePassed);
  }
}

用法

<app-upload-field [labelName]="'Blader'" (myValueChanged)="parentEvent($event)" [placeHolderValue]="'Kies bestand'"></app-upload-field>

在父组件中

 parentEvent(data:string){
    // do something with data
    }

参考this link了解更多详情。

@Output 从指令向父组件发出值 Angular 4

@Output emit value from directive to parent component Angular 4

angularjs-directive

angular