Angular Firebase在数据库中创建子项

Question

所以我已将业务信息上载到数据库（createItemAuth()），并且我正试图将数据库中的子项将卡车和拖车上载到公司，但这是行不通的。那就是我的尝试：

export interface Trucks {
  name: string;
}

export interface Trailers {
  name: string;
}


export interface Data {
  name: string;
  address: string;
  address2: string;
  pscode: string;
  ccode: string;
  name2: string;
  trucks: Trucks;
  trailers: Trailers;
}
export class BackService {
  constructor(private afDatabase: AngularFireDatabase,     private afAuth: AngularFireAuth ) {
    this.busCollection = this.afDatabase.list(`imones`);
  }
  busines = {} as Data;
  createItemAuth() {
    this.afAuth.authState.subscribe(auth => {
      this.afDatabase.object(`${auth && auth.email && auth.uid}/company/`).update(this.busines)
        });
    }

createTruckAuth() {
    this.afAuth.authState.subscribe(auth => {
      this.afDatabase.list(`${auth && auth.email && auth.uid}/company/trucks/`).push(this.busines.trucks)
    });
  }
  createTrailAuth() {
    this.afAuth.authState.subscribe(auth => {
      this.afDatabase.list(`${auth && auth.email && auth.uid}/comapny/trails/`).push(this.busines.trailers)
    });
  }

创建HTML：

<input [(ngModel)]="back.busines.name" type="text">
      <input [(ngModel)]="back.busines.address" type="text">
      <input [(ngModel)]="back.busines.address2" type="text">
      <input [(ngModel)]="back.busines.trucks.name" type="text">
      <input [(ngModel)]="back.busines.trailers.name" type="text">
      <button (click)="back.createTruckAuth();back.createTrailAuth();back.createItemAuth();back.createItem()">create truck</button>
<p *ngFor="let car of carsData" status="success" class="col-sm-4">{{car.name}}></p>

如何在数据库中创建子项，以便我可以发布信息？