Question

我目前正在尝试使用googles firebase构建一些东西，我遇到了一个问题。看来这段代码

    export class FirebaseService {
    items: Observable<Item[]>;

    constructor(private db: AngularFireDatabase){

    }

    getBusinesses(){
        this.businesses = this.db.list('/items').valueChanges() as Observable<Item[]>
        return this.items;
    }

}

用于为您提供一个带有$ key的对象作为数据库中对象的键（至少这是我在阅读的教程中所做的）

问题是，$ key是未定义的，我想知道，我如何获得list-method返回包含密钥的对象。一直在尝试一段时间，但我真的找不到错误。如果有人知道答案，我会很高兴。

[编辑]

https://github.com/angular/angularfire2/blob/master/docs/version-5-upgrade.md 这让我更接近解决方案。看来，angularfire2已经看到了5.0.0版本的一些重大变化。但是由于我还在学习，我无法将它真正集成到我的代码中。目前它看起来像这样

firebase.service.ts

import { Injectable } from '@angular/core';
import { AngularFireModule } from 'angularfire2';
import { AngularFireDatabase, AngularFireDatabaseModule } from 'angularfire2/database';
import { FirebaseListObservable } from 'angularfire2/database-deprecated';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/map';
import {Business} from '../Business';
import {Category} from '../Category';

@Injectable()
export class FirebaseService {
    businesses : Observable<Business[]>;
    categories : Observable<Category[]>;

    constructor(private db: AngularFireDatabase){

    }

    getBusinesses(){
        this.businesses = this.db.object('/businesses').snapshotChanges().map(action => {
            console.log('ACTION:');
            console.log(action);
            const $key = action.payload.key;
            const data = {$key, ...action.payload.val()};
            return data;
        }) as Observable<Business[]>;
        return this.businesses;
    }
}

和app.component.ts

import { Component, OnInit } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';
import { Observable } from 'rxjs/Observable';
import { FirebaseService } from './services/firebase.service';
import { Business } from './Business';
import { Category } from './Category';

@Component({
    selector: 'app-root',
    templateUrl: './app.component.html',
    styleUrls: ['./app.component.css']
})
export class AppComponent {
    title = 'app';
    items: Observable<any[]>;
    businesses: Business[];
    categories: Category[];
    appState: string;
    activeKey: string;

    constructor(private _firebaseService: FirebaseService){

    }

    ngOnInit(){
        this._firebaseService.getBusinesses().subscribe(businesses => {
            console.log('Businesses:');
            console.log(businesses);
            this.businesses = businesses;
        });
    }


}

现在我的结果并不像我希望的那样。基本上我要回来的是

{
    0: {
        Key01: "xyz",
        Key02: "yyy"
    },
    1: {
        Key11: "zyx",
        Key12: "zzz"
    },
    $key: "businesses"
}

我会继续努力。也许你知道我做错了什么。感谢您的帮助到目前为止

[/编辑]

Answer 1

您需要将项目声明为FirebaseListObservable<Item[]>并执行getBusinesses（）调用，如下所示：

this.items= this.af.list('/items') as FirebaseListObservable<Item[]>;

希望这会帮助您获得$ key值。

检索firebase数据库中的id

1 个答案: