无法从 Angular5 模板中的 firebase 获取 $key [英] Unable to fetch $key from firebase in Angular5 template

问题描述

我正在 Angular5 中使用 firebase 在后端制作表单.该表单包含几个输入字段和一个下拉列表.

我可以在下拉选项中填充值 ({{ c.name }}) 但选项的 value 属性为空，我正在尝试使用 c.$key 填充.

以下是 HTML 部分:

<!-- 这里的其他输入字段--><div class="form-group"><label for="category">Category</label><select ngModel name="category" id="category" class="form-control"><option value=""></option><option *ngFor="let c of Categories$ | async" [value]="c.$key">{{ c.name }}</选项></选择>

</表单>

这是我的组件:

import { CategoryService } from './../../category.service';从@angular/core"导入 { Component, OnInit };@成分({选择器:'app-product-form'，templateUrl: './product-form.component.html',styleUrls: ['./product-form.component.css']})导出类 ProductFormComponent 实现 OnInit {类别$;构造函数(类别服务:类别服务){this.categories$ = categoryService.getCategories();}ngOnInit() {}保存(产品){控制台日志(产品)；}}

服务:

import { Injectable } from '@angular/core';从 'angularfire2/database' 导入 { AngularFireDatabase };@Injectable()导出类 CategoryService {构造函数(私有数据库:AngularFireDatabase){}获取类别(){return this.db.list('/categories', ref => ref.orderByChild('name')).valueChanges();}}

我正在控制台上打印表单 json 的值.类别的值即将未定义.

{title: "Title", price: 10, category: "undefined", imageUrl: "xyz"}

请指导我我错过了什么.

解决方案

$key 已弃用.改用 snapshotChanges().

category.service.ts

getCategories() {返回这个.db.list('/categories', (ref) => ref.orderByChild('name')).snapshotChanges().管道(地图((动作)=> {返回 actions.map((action) => ({键:action.key，val: action.payload.val(),}));}));}

app.component.html

{{ c.val.name }}</选项>

I am making a form in Angular5 using firebase in backend. The form contains few input fields and a dropdown.

I'm able to populate values ({{ c.name }}) in dropdown options but value attribute of option is coming empty which I'm trying to populate using c.$key.

Below is the HTML part:

<form #f="ngForm" (ngSubmit)="save(f.value)">
    <!-- other input fields here -->
    <div class="form-group">
        <label for="category">Category</label>
        <select ngModel name="category" id="category" class="form-control">
          <option value=""></option>
          <option *ngFor="let c of categories$ | async" [value]="c.$key"> 
            {{ c.name }} 
          </option>
        </select>
    </div>
</form>

Here is my component:

import { CategoryService } from './../../category.service';
import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-product-form',
  templateUrl: './product-form.component.html',
  styleUrls: ['./product-form.component.css']
})
export class ProductFormComponent implements OnInit {
  categories$;

  constructor(categoryService: CategoryService) {
    this.categories$ = categoryService.getCategories();
  }

  ngOnInit() {
  }

  save(product) {
    console.log(product);
  }

}

Service:

import { Injectable } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';

    @Injectable()
    export class CategoryService {

      constructor(private db: AngularFireDatabase) { }

      getCategories() {
        return this.db.list('/categories', ref => ref.orderByChild('name')).valueChanges();
      }
    }

I'm printing value of form json on console. The value of category is coming undefined.

{title: "Title", price: 10, category: "undefined", imageUrl: "xyz"}

Please guide me what am I missing.

解决方案

$key has been deprecated. Use snapshotChanges() instead.

category.service.ts

getCategories() {
    return this.db
        .list('/categories', (ref) => ref.orderByChild('name'))
        .snapshotChanges()
        .pipe(
        map((actions) => {
            return actions.map((action) => ({
                key: action.key,
                val: action.payload.val(),
            }));
        }));

}

app.component.html

<option *ngFor="let c of categories$ | async" [value]="c.key">
    {{ c.val.name }}
</option>

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