Angular 如何通过更改其他下拉列表过滤一个下拉列表

我从angular开始，在我的项目中，我有两个下拉列表，第一个下拉列表：

<mat-form-field appearance="fill" class = "tp-full-width">
            <mat-select  #captionlist2 (selectionChange)="filterByCaption($event)"> 
                 <mat-option  *ngFor="let p of list_product.data" [value]="p">
                       {{ p.description }}
                  </mat-option>
             </mat-select>
</mat-form-field>

   <mat-form-field appearance="fill" class = "tp-full-width">
           <mat-select  #brandlist (selectionChange)="filterByBrands($event)">
                  <mat-option  *ngFor="let m of list_brands.data" [value]="m">
                              {{ m.BDesc }}
                   </mat-option>
            </mat-select>
    </mat-form-field>

filterByCaption(event: any)
          {
            console.log(event.value.id);
            this.list_brands.filterPredicate = 
             (data, filter: string) => data.brandcode== event.value.id;
               this.list_brands.filter=event.value.id;
          }

还可用于onchange标题下拉列表：

<mat-form-field appearance="fill" class = "tp-full-width">
            <mat-select  #captionlist2 (selectionChange)="filterByCaption($event)"> 
                 <mat-option  *ngFor="let p of list_product.data" [value]="p">
                       {{ p.description }}
                  </mat-option>
             </mat-select>
</mat-form-field>

   <mat-form-field appearance="fill" class = "tp-full-width">
           <mat-select  #brandlist (selectionChange)="filterByBrands($event)">
                  <mat-option  *ngFor="let m of list_brands.data" [value]="m">
                              {{ m.BDesc }}
                   </mat-option>
            </mat-select>
    </mat-form-field>

filterByCaption(event: any)
          {
            console.log(event.value.id);
            this.list_brands.filterPredicate = 
             (data, filter: string) => data.brandcode== event.value.id;
               this.list_brands.filter=event.value.id;
          }

---

但是第二个下拉列表不能通过选择更改第一个下拉列表进行过滤，我该怎么做？

它看起来像是

list\u品牌

，

list\u产品

的类型如下：

interface YourFilterList<T> {
    data: T[];
    filterPredicate: (d: T, filter: string) => boolean;
    filter: string;
}

---

只要让管道谁将返回过滤数组，如果选择的东西，如果第一个dd或无，如果第一个是空的