嵌套数组对象和角度数组

Question

找到下面的数组和对象以及我需要调用的数组的数据， 将名称sectionId = name; shiftId = name转换为具有id：_id的html角材料以传递到component.ts，

***************数据****************

"mainData": [{
    "gradeId": {
      "organId": "5a90152",
      "name": "primary",
    },
    "clSectionId": [{
        "sectionId": {
          "_id": "533d06",
          "organId": "5a90152",
          "name": "AA",
        },
        "shiftId": [{
            "_id": "b1fbfe",
            "name": "MORNING",
            "organId": "5a90152"
            "days": [
              "Monday"
            ]
          },
          {
            "_id": "03de8a",
            "name": "EVENING",
            "organId": "5a90152",
            "days": [
              "Monday",
              "Tuesday",
              "Wednesday",
              "Thursday",
              "Friday"
            ]
          }
        ]
      }
    }
  ]

************ html ***********

<mat-form-field>
  <mat-select 
    placeholder="Grade" 
    [(ngModel)]="selectedValue" 
    (change)="changefunction($event)" 
    name="grade">
    <mat-option 
      *ngFor="let class of classes" 
      [value]="class.gradeId._id">
      {{class.gradeId.name}}
    </mat-option>
  </mat-select>
</mat-form-field>