如何在Angular中显示/隐藏按钮

当按钮状态为“批准”并且“批准”按钮为“待定”状态时，我想显示“拒绝”按钮。我正确传递了值，但两个按钮始终显示。

这是我的.ts文件

    export class NotificationComponent implements OnInit {

      notices: notification[] = [];
      public approve_show: boolean = false;
      public disapprove_show: boolean = false;

      constructor(
        private http: HttpClient,
        private router: Router,
      ) { }

      ngOnInit() {

    var url = "http://localhost:3000/notification/view";

    this.http.get<any>(url).subscribe(res => {
      this.notices = res;
      var i = 0;

      for (var prop in res) {
        if (res.hasOwnProperty(prop)) {
          // console.log(res[i].state)          
          if (res[i].state == 'Approved') {
            console.log("approved")
            this.disapprove_show = true
          }
          else {
            this.approve_show = true
          }
          i++;
        }
      }

    }, (err) => {
      console.log(err);
    });
  }
}

这是我的html代码

<button *ngIf="approve_show" mat-raised-button class="approve_btn">Approve</button>
<button *ngIf="disapprove_show"  mat-raised-button color="warn" style="width:100px;">Disapprove</button>