我想将https://github.com/lipis/flag-icon-css与ionic-select和https://www.npmjs.com/package/ionic-selectable一起使用。安装软件包后，我尝试了许多方法，但仍然无法显示该标志。有人可以给我解释一下这些标志如何工作

ionic_select.html

<ion-select #select1 [(ngModel)]="selectedCode">
<ion-select-option *ngFor="let c of countries" value="{{c.flag}}{{c.code}}">{{c.flag}}{{c.name}}</ion-select-option>
</ion-select>

ionic_select.ts

countries: any = [
{
  code: '+93',name: 'Afghanistan',flag: './assets/flags/af.png'
},

ionic_selectable.html

 <ion-item>
 <ionic-selectable
 item-content
 [(ngModel)]="port"
 [items]="ports"
 itemTextField="country"

 [canSearch]="true"
 (onChange)="portChange($event)"


 </ionic-selectable>
<span class="flag-icon flag-icon-{flag}"></span>
 </ion-item>

ionic_selectable.ts

class country {
public country: string;
public flag: string;

}
export class Classname {
  ports: country[]; 
  port: country;  
this.ports = [
 constructor(){
  {
    country: 'afghanistan',flag: './assets/flags/af.png'
  },}