Question

我正在使用角度6，“ @ angular / fire”：“ ^ 5.1.1”，“ firebase”：“ ^ 5.6.0”，我想获取数据库中的所有数据，但没有得到它，我尝试了很多方法，这是我的appmodule.ts：

          import { BrowserModule } from '@angular/platform-browser';
      import { NgModule } from '@angular/core';
      import { AngularFireDatabaseModule } from '@angular/fire/database';
      import {AngularFireModule} from '@angular/fire';
      import {environment} from '../environments/environment';

      import { AppComponent } from './app.component';


      @NgModule({
        declarations: [
          AppComponent,

        ],
        imports: [
          BrowserModule,
          AngularFireDatabaseModule,
          AngularFireModule.initializeApp(environment.firebase),
        ],
        providers: [],
        bootstrap: [AppComponent]
      })
      export class AppModule { }

...这是我的appcomponent：

      import { Component, OnInit} from '@angular/core';
      import { AngularFireDatabase } from '@angular/fire/database';
      //import 'rxjs/add/operator/map';
      import {Observable} from 'rxjs';

      @Component({
        selector: 'app-root',
        templateUrl: './app.component.html',
        styleUrls: ['./app.component.css']
      })
      export class AppComponent implements OnInit {


        courses: Observable<any[]>;

          constructor(private db: AngularFireDatabase){
              this.courses=db.list('/courses').snapshotChanges();
          }

            getData(){
              return this.courses;
            }

          ngOnInit(){
              console.log(this.getData());
              debugger;
          }
      }

.... i也尝试过：

this.courses=db.list('/courses').valueChanges();

...和

this.courses=db.list('/courses').subscribe(courses=>{
                this.courses=courses;
              });

Answer 1

snapshotChanges返回一个可观察值。我们需要订阅可观察对象以获取数据。

 constructor(private db: AngularFireDatabase){
      db.list('/courses').snapshotChanges().subscribe((response) => {
             this.courses= response;
      });
 }

Answer 2

从文档中：

valueChanges（）： The current state of your collection. Returns an Observable of data as a synchronized array of JSON objects. All Snapshot metadata is stripped and just the method provides only the data.

您应该订阅该函数返回的Observable，所以：

courses: Observable<CourseModel[]> | Observable<any> | any;
constructor(private db: AngularFireDatabase){
  this.courses=db.list('/courses').valueChanges()
    .subscribe(courses => {
      console.log(courses); // Check the returned values;
      this.courses = courses;
    })
}

我没有从Firebase实时数据库中获取数据到angular 6

2 个答案: