ng- select :如何选择多个标签相同但对象不同的项目

Question

我正在尝试修补ng-select下拉列表中的多个选定项。我没有指定任何bindValue，所以这些项应该通过object进行绑定(在https://www.npmjs.com/package/@ng-select/ng-select中指定)

但在尝试执行此操作时，项不会根据对象而是根据显示的标签进行选择。而且，只有第一个标签会被选中。

示例: app.component.html

<form [formGroup]="group">
    <div class="form-group" formGroupName="school">
        <ng-select labelForId="school" placeholder="Select school" [items]="schools" formControlName="code"
            bindLabel="displayLabel" multiple="true" groupBy="city">
        </ng-select>
    </div>
</form>

app.component.ts

import { Component, OnInit } from '@angular/core';
import { FormBuilder, FormGroup, FormControl, Validators } from '@angular/forms';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {
  group: FormGroup;
  schools = [];
  constructor(private fb: FormBuilder) { }

  ngOnInit() {
    this.initSchools();
    const formModel = {
      school: new FormGroup({
        code: new FormControl(null, Validators.required)
      })
    }
    this.group = this.fb.group(formModel);
    this.group.patchValue({
      school: {
        code:
          [
            {
              schoolId: 'SC003',
              displayLabel: 'Test-3 school',
              city: "City1"
            },
            {
              schoolId: 'SC005',
              displayLabel: 'Test-3 school',
              city: "City5"
            }
          ]
      }
    });
  }

  initSchools() {
    this.schools.push(
      {
        schoolId: 'SC001',
        displayLabel: 'Test-1 school',
        city: "City1"
      },
      {
        schoolId: 'SC002',
        displayLabel: 'Test-2 school',
        city: "City2"
      },
      {
        schoolId: 'SC003',
        displayLabel: 'Test-3 school',
        city: "City3"
      },
      {
        schoolId: 'SC004',
        displayLabel: 'Test-4 school',
        city: "City4"
      },
      {
        schoolId: 'SC005',
        displayLabel: 'Test-3 school',
        city: "City5"
      }
    );
  }
}

在上面的示例中，只有item的对象

    {
      schoolId: 'SC003',
      displayLabel: 'Test-3 school',
      city: "City1"
    },

被选中，

而下面的项目并不

    {
      schoolId: 'SC005',
      displayLabel: 'Test-3 school',
      city: "City5"
    }

应该怎么做才能让两个项目都在下拉列表中被选中(提供唯一的对象)。这里有没有遗漏什么。任何其他实现这一目标的方法。

在这里运行示例：https://stackblitz.com/edit/angular-szel64?file=src%2Fapp%2Fapp.component.ts

Answer 1

我发现对于ng-select有一个compareWith选项，它允许您定义一个函数来比较对象。使用此选项，您可以绑定对象，并根据compareWith选项提供的功能将其选中。

下面是我的更改，以防任何人遇到同样的问题

app.component.html

<form [formGroup]="group">
    <div class="form-group" formGroupName="school">
        <ng-select labelForId="school" placeholder="Select school" [items]="schools" formControlName="code"
            bindLabel="displayLabel" multiple="true" groupBy="city"
      [compareWith]="compareFunction">
        </ng-select>
    </div>
</form>

app.component.ts

...
  compareFunction(item, selected) {
// any logic to compare the objects and return true or false
    return item.schoolId === selected.schoolId
  }
...