angular - 尽管有数据源，但 mat-table angular 6 不显示任何数据

Question

我想通过Angular material design的数据表mat-table展示一个列表。 这是我的组件:

import { LeaveapplicationService } from './../../services/leaveapplication.service';
import { leaveapplication } from './../../models/leaveapplication';
import { Component, OnInit, ViewChild, Input } from '@angular/core';
import { MatTableDataSource, MatPaginator, MatSort } from '@angular/material';
// import { DataSource } from '@angular/cdk/table';

@Component({
  selector: 'app-leaveapplication-list',
  templateUrl: './leaveapplication-list.component.html',
  styleUrls: ['./leaveapplication-list.component.scss']
})
export class LeaveapplicationListComponent implements OnInit {
  leaveApplications: leaveapplication[];
  displayedColumns: ['id', 'applicant', 'manager', 'leavetype', 'start', 'end', 'return', 'status'];
  dataSource: MatTableDataSource<leaveapplication>;

  constructor(private leaveApplicationService: LeaveapplicationService) { }

  @ViewChild(MatPaginator) paginator: MatPaginator;
  @ViewChild(MatSort) sort: MatSort;

  ngOnInit() {
    this.leaveApplicationService.getLeaveApplications().subscribe(leaveapplications => {
      this.leaveApplications = leaveapplications;
      this.dataSource = new MatTableDataSource<leaveapplication>(this.leaveApplications);
      this.dataSource.paginator = this.paginator;
      this.dataSource.sort = this.sort;
      console.log(this.dataSource);
    });

  }

  applyFilter(filterValue: string) {
    filterValue = filterValue.trim(); // Remove whitespace
    filterValue = filterValue.toLowerCase(); // MatTableDataSource defaults to lowercase matches
    this.dataSource.filter = filterValue;
  }
}

休假申请接口(interface):

export interface leaveapplication {
  id: number; 
  applicant: string;
  manager: string;
  startdate: Date;
  enddate: Date;
  returndate: Date;
  leavetype: string; 
  status: string;
}

我正在控制台中正确获取数据源:

但是 mat-table 返回空单元格:

这是我的模板:

<mat-form-field>
  <input matInput (keyup)="applyFilter($event.target.value)" placeholder="Filter">
</mat-form-field>
<mat-table #table [dataSource]="dataSource" matSort class="mat-elevation-z8">
  <ng-container matColumnDef="id">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> Form ID </th>
    <td mat-cell *matCellDef="let leaveapplication"> {{leaveapplication.id}} </td>
  </ng-container>
  <ng-container matColumnDef="applicant">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> Applicant </th>
    <td mat-cell *matCellDef="let leaveapplication"> {{leaveapplication.applicant}} </td>
  </ng-container>

  <ng-container matColumnDef="manager">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> Manager </th>
    <td mat-cell *matCellDef="let leaveapplication"> {{leaveapplication.manager}} </td>
  </ng-container>

  <ng-container matColumnDef="leavetype">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> Leave Type </th>
    <td mat-cell *matCellDef="let leaveapplication"> {{leaveapplication.leaveType}} </td>
  </ng-container>
  <ng-container matColumnDef="start">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> Start Date </th>
    <td mat-cell *matCellDef="let leaveapplication"> {{leaveapplication.startDate | date:'dd-MM-yyyy'}} </td>
  </ng-container>
  <ng-container matColumnDef="end">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> End Date </th>
    <td mat-cell *matCellDef="let leaveapplication"> {{leaveapplication.endDate | date:'dd-MM-yyyy'}} </td>
  </ng-container>
  <ng-container matColumnDef="return">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> Return Date </th>
    <td mat-cell *matCellDef="let leaveapplication"> {{leaveapplication.returnDate | date:'dd-MM-yyyy'}} </td>
  </ng-container>
  <ng-container matColumnDef="status">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> Status </th>
    <td mat-cell *matCellDef="let leaveapplication"> {{leaveapplication.status}} </td>
  </ng-container>
  <tr mat-header-row *matHeaderRowDef="displayedColumns"></tr>
  <tr mat-row *matRowDef="let row; columns: displayedColumns;"></tr>
</mat-table>

<mat-paginator [pageSizeOptions]="[5, 10, 20]" showFirstLastButtons></mat-paginator>

为什么我没有填充 mat-table？是因为响应的异步性质吗？

Answer 1

您好，我有一个类似的问题，我可以记录数据源的数据，但数据表不显示数据。

我在我的服务中创建了一个模拟数据数组，并传递了它而不是我从数据库中获得的结果。使用 Mock-Array 它可以正常工作，并且我在我的 mat-table 中填充了数据。

在我记录了数据库和 Mock-Data 的结果后，在控制台中我注意到我从我的数据库中得到了一个包含数组的对象，而不仅仅是一个数组。

浏览器控制台 ->

模拟数据:[ {...} ]

数据库:{ [ {...} ] }

如果仔细观察，您会在浏览器 DOM 中看到，数据源设置为 [Object object]，我认为存在问题，因为 Mat-Table 无法访问数据。

我找到了一个解决方法，我传递了对象的数组而不是对象，这有点脏，但在我找到问题的根源之前完成了这项工作。

这是我的服务:

rfc.service.ts

@Injectable({
  providedIn: 'root'
})
export class RfcService {
  rfcsChanged = new Subject<Rfc[]>();
  private dbSubs: Subscription[] = [];

  <<MOCK-DATA>>

  constructor(private http: HttpClient) { }

  httpOptions = {
    headers: new HttpHeaders({
      'Content-Type': 'application/json'
    })
  };

  fetchRfcs() {...}

  cancelSubscriptions() {
    this.dbSubs.forEach(sub => sub.unsubscribe());
  }

在我更改了我的代码之后:

fetchRfcs() {
  this.dbSubs.push(
    this.http.get<Rfc[]>('http://localhost:3000/rfcs')
     .subscribe((rfcs: Rfc[]) => {
       // console.log(this.MOCK_RFCS);
       // console.log(rfcs);
       this.rfcsChanged.next(rfcs); 
     })
  );
}

到:

fetchRfcs() {
  this.dbSubs.push(
    this.http.get<Rfc[]>('http://localhost:3000/rfcs')
     .subscribe((rfcs: Rfc[]) => {
        // console.log(this.MOCK_RFCS);
        // console.log(rfcs.rfcs);
        this.rfcsChanged.next(rfcs.rfcs); 
     })
    );
}

它起作用了。

我不知道为什么我的响应数组被包裹在一个对象中，但我建议检查您的服务以及它如何接收数据。目前，我试图找到一种方法来映射来自后端的响应，这样它就不会被包裹在一个对象中。

您如何在您的服务中检索数据？