Question

在Angular 7项目中，我有一个带有select和*ngFor块的反应形式。 ngFor值是根据选项中的选定值进行过滤的，而自定义管道负责过滤。每当我从选项中选择一个值时，我只会看到"[object Object]"的输出。我尝试了(ngModelChange)=fun()，change个事件。他们没有工作。

表格：

<div class="container container-fluid">
  <h3 style="text-align: center"> BCMC CyberSecurity Jobs</h3>
  <form [formGroup]="jobsForm">
  <div class="row" style="margin-top: 40px">
    <div class="col-xs-6 col-sm-6 col-md-6 col-lg-6">
        <label> Job Type:
          <select class="custom-select" formControlName="jobTypeControl" (ngModelChange)="updateFilterValue($event)">
            <option *ngFor="let jobType of jobTypeObservable" [value]="jobType"> {{jobType.name}}</option>
          </select>
        </label>
    </div>

    <div *ngIf="jobsDataAvailable()" class="col-xs-6 col-sm-6 col-md-6 col-lg-6">
      <div class="has-text-centered">
        <pagination-controls (pageChange)="page = $event" class="my-pagination" directionLinks="true" maxSize="5"
                             nextLabel="" previousLabel=""></pagination-controls>
      </div>
    </div>
  </div>

  <div *ngIf="jobsDataAvailable()">
    <div *ngFor="let job of (jobsObservable) | stringFilter: this.jobsForm.controls['jobTypeControl'].value  | paginate: { itemsPerPage: 10, currentPage: page }" class="row" style="margin-top: 10px">
      <div class="col-xs-12 col-sm-12 col-md-12 col-lg-12">
        <div class="card">
          <div class="card-body">
            <h5 class="card-title">{{job.title}}</h5>
            <h6 class="card-subtitle mb-2 text-muted">{{job.city}}, {{job.state}}</h6>
            <p class="card-text">This text will be replaced by clearance value in future</p>
            <a class="btn btn-primary" href="https://bcmcllc.applytojob.com/apply/{{job.board_code}}">View and Apply</a>
          </div>
        </div>
      </div>
    </div>
  </div> <!-- End of ngIf-->
  </form>

</div>

自定义过滤器：

 import {Pipe, PipeTransform} from "@angular/core";

    @Pipe({
      name: 'stringFilter'
    })
    export class StringFilterPipe implements PipeTransform
    {

      transform(value: string[], filterValue: any)
      {
        if (!filterValue || filterValue === '')
        {
          return value;
        }
        return value.filter(item => -1 < item.toLowerCase().indexOf(filterValue.toLowerCase()));
      }
    }


**JobsListComponent**

import {Component, OnChanges, OnInit, SimpleChanges} from '@angular/core';
import {JobsService} from './services/jobs.service';
import {SERVER_API_URL} from '../../app.constants';
import {Observable} from 'rxjs';
import {Job} from './model/job';
import {FormControl, FormGroup} from '@angular/forms';
import {JobType} from './model/job-type';

@Component({
  selector: 'app-jobs-list',
  templateUrl: './jobs-list.component.html',
  styleUrls: ['./jobs-list.component.css']
})

export class JobsListComponent implements OnInit
{
  jobsObservable: Observable<Job[]>;
  jobTypeObservable: Observable<JobType[]>;
  page: number = 1;

  jobsForm = new FormGroup({
    jobTypeControl: new FormControl({value: '', disabled: false})
  });

  //this.form.controls['jobTypeControl'].value
  //jobsForm.get('jobTypeControl').value
  constructor(private jobsService: JobsService) {
  }

  ngOnInit()
  {

    this.getAllJobTypes();
    this.getAllJobs();
  }

  getAllJobs() {
    let url = SERVER_API_URL + 'jobs/all';

    this.jobsService.getAllJobs(url).subscribe(
      data => {
        // @ts-ignore
        this.jobsObservable = data;
      },
      error => console.error('Failed to retrieve values from backend, error=> ' + error),
      () => console.log('Jobs retrieved from backend'));
    return this.jobsObservable;
  }

  getAllJobTypes() {
    let url = SERVER_API_URL + 'jobtypes/all';

    this.jobsService.getAllJobTypes(url).subscribe(
      data => {
        // @ts-ignore
        this.jobTypeObservable = data;
      },
      error => console.error('Failed to retrieve values from backend, error=> ' + error),
      () => console.log('Job Types retrieved from backend'));
    return this.jobTypeObservable;
  }

  jobsDataAvailable() {
    return this.jobsObservable !== undefined;
  }


  updateFilterValue(event)
  {
    console.log("Emitted Value "+event);
  }
}

Answer 1

两件事。

首先：您可以选择

<option *ngFor="let jobType of jobTypeObservable" [value]="jobType"> 
      {{jobType.name}}
</option>

因此，该值是jobType类型的对象，可以使用例如。如果您的jobType具有名为“ id”的属性[value] = jobType.id

<option *ngFor="let jobType of jobTypeObservable" [value]="jobType.id"> 
      {{jobType.name}}
</option>

因此，您在函数中收到的是“ id”，而不是整个对象

第二个：通常在反应形式中，您订阅值更改-不使用（更改）-。然后，在创建表单后

jobsForm.get('jobTypeControl').valueChanges.subscribe(value=>
   { //here you has the value of jobTypeControl
      console.log(value)
   }
)

选择表单控件在Angular 7中返回[object Object]

1 个答案: