问TypeError: this.mealService.getCardAssignment不是函数Angular 8

EN

<kendo-grid [data]="allData"
              kendoGridSelectBy="id"
              [selectedKeys]="mySelection"
              [pageSize]="pageSize" [skip]="skip" [sort]="gridState.sort"
              [pageable]="true"
              [sortable]="true"
              [reorderable]="true"
              [resizable]="true"
              [scrollable]="true"
              [columnMenu]="{ filter: true }"
              (edit)="onEdit($event)"
              (remove)="onRemove($event)"
              (add)="onAdd($event)">

<kendo-grid [data]="cardAssignment"
                      [pageable]="true"
                      [sortable]="true"
                      [reorderable]="true"
                      [resizable]="true"
                      [scrollable]="true">

this.mealService.getCardAssignment(bookedByData).subscribe(
      (resp: any) => {
        console.log(resp);
        this.guestsPerEmployee = resp;
      },
      (err: any) => {
        //ON ERROR
      },
      () => {
        //ON Success
        this.loadCardAssignmentGrid();
      }
    );

getCardAssignment(params: any) {
    return this.api.post('v1/employees/GetCardAssignment', params);
  }