来自ws的角度过滤数据显示为空

Question

我从ws正确获取所有城市，但是当我在其他过滤城市使用时是空数组。请关注我的代码。

    client: Client;
     cities: City[] = [];
     selectedCity: string;
     filteredOptionsCity: any;
     city_id: FormControl = new FormControl();
     myform: FormGroup;
      constructor(public fb: FormBuilder) {


    this.myform = this.fb.group({
      'city_id': new FormControl('', Validators.required),
      'client_name': new FormControl('', Validators.required),
      'email': new FormControl('', Validators.required)
    });
  }

    ngOnInit() {
        this.populateForm();
        this.ws.allcity().subscribe(
            cities => {
                this.cities = cities.map((city) => {
                    return new City(city);
                });
                console.log(cities) //return all my city correctly
            }
        );
        this.filteredOptionsCity = this.city_id.valueChanges.pipe(
            startWith(''),
            map(value => this.filterCity(value))
        );
        this.selectedCity = this.cities.filter(
            x => x.city_id === this.client.city
                .map(x => x.city_id)[0])
            .map(y => y.name).join('')
        console.log(this.cities) //cities are empty
    }
    }

    populateForm() {
        this.activatedRoute.params.subscribe(
            params => {
                this.ws.getClientById(params['id']).subscribe(
                    client => {
                        this.client = client;
                        this.patchForm();
                    }
                );
            }
        );
    }
    patchForm() {
        this.myform.controls['client_name'].setValue(this.client.clientName);
        this.myform.controls['email'].setValue(this.client.email);
        this.myform.controls['city_id'].setValue(this.client.city);
    }
    filterCity(val: string): City[] {
        if (val) {
            let filterValue = val.toString();
            return this.cities.filter(city => city.name.toString().startsWith(filterValue));
        }

        return this.cities;
    }

我想过滤城市，我尝试过滤，但在此代码中，我的城市是空的。

     this.selectedCity = this.cities .filter(
          x => x.city_id === this.client.city
          .map(x => x.city_id)[0])
          .map(y => y.name).join('')
          console.log(this.cities ) //cities are empty
         }

我有一个例子，这个逻辑运行良好，但是当我使用来自ws的数据时，这对我不起作用。 DEMO Example