如何在特定条件下从angular 8中的formarray中选中复选框

import { Component } from '@angular/core';
import { FormBuilder, FormArray, FormControl } from '@angular/forms';

@Component({
  selector: 'app-dynamic-form',
  templateUrl: './dynamic-form.component.html',
  styleUrls: ['./dynamic-form.component.css']
})
export class DynamicFormComponent {
  dynamicForm = this.fb.group({
    checkboxes: this.fb.array([])
  });

  constructor(private fb: FormBuilder) {
    this.addCheckbox();
  }

  get checkboxes() {
    return this.dynamicForm.get('checkboxes') as FormArray;
  }

  addCheckbox() {
    const checkbox = this.fb.control(false);
    this.checkboxes.push(checkbox);
  }

  selectCheckboxes(condition: boolean) {
    this.checkboxes.controls.forEach(control => {
      control.setValue(condition);
    });
  }
}

<form [formGroup]="dynamicForm">
  <div formArrayName="checkboxes">
    <div *ngFor="let checkbox of checkboxes.controls; let i = index" [formGroupName]="i">
      <input type="checkbox" formControlName="checked"> Checkbox {{ i + 1 }}
    </div>
  </div>
  <button (click)="selectCheckboxes(true)">Select All</button>
  <button (click)="selectCheckboxes(false)">Deselect All</button>
</form>