角度数组长度未定义

Question

我在角度模型中定义了以下代码段。但是当我尝试在组件中获取数组的长度时，它表示未定义。我无法弄清楚发生了什么。请任何人帮助我。提前致谢。

import {Injectable} from "@angular/core";

@Injectable()
export class Bus{

  unique_id : string = '';
  bus_number : string = '';
  name : string = '';
  make : string = '';
  model : string = '';
  owner_id : string = '';
  merchant_route_id : string;
  features : any = [];
  selected_features : any = [];
  active_bus_images : any = [];

  constructor(){}

}

我的服务代码段

private bus: Bus = new Bus();
private busImage: BusImage = new BusImage();

getBus(): Bus {
    var bus: Bus = {
      name: this.bus.name,
      bus_number: this.bus.bus_number,
      make: this.bus.make,
      model: this.bus.model,
      unique_id: this.bus.unique_id,
      owner_id: this.bus.owner_id,
      features: this.bus.features,
      active_bus_images: this.bus.active_bus_images,
      merchant_route_id : this.bus.merchant_route_id,
      selected_features : this.bus.selected_features
    };
    console.log(this.bus.selected_features)
    return bus;
}

组件中的代码段

this.bus = this.busService.getBus();
for (let item2 of this.tempFeatuers) {
   this.feature2.id = item2.unique_id;
   this.feature2.itemName = item2.name;
   this.dropdownList.push(Object.assign({}, this.feature2));
}

console.log(this.bus.selected_features.length); // says undefined