ngClass未看到通过服务订阅更新的变量

<div [ngClass]="{'class-name': isClassActive}">
  <!-- HTML内容 -->
</div>

import { Component, OnInit } from '@angular/core';
import { YourService } from 'your-service';

@Component({
  selector: 'your-component',
  templateUrl: 'your-component.html',
  styleUrls: ['your-component.css']
})
export class YourComponent implements OnInit {
  isClassActive: boolean;

  constructor(private yourService: YourService) {}

  ngOnInit() {
    this.yourService.variable.subscribe((value) => {
      this.isClassActive = value;
    });
  }
}

import { Injectable } from '@angular/core';
import { BehaviorSubject } from 'rxjs';

@Injectable()
export class YourService {
  variable: BehaviorSubject<boolean> = new BehaviorSubject<boolean>(false);

  updateVariable(value: boolean) {
    this.variable.next(value);
  }
}

import { Component } from '@angular/core';
import { YourService } from 'your-service';

@Component({
  selector: 'your-other-component',
  template: `
    <button (click)="updateVariable(true)">Activate</button>
    <button (click)="updateVariable(false)">Deactivate</button>
  `
})
export class YourOtherComponent {
  constructor(private yourService: YourService) {}

  updateVariable(value: boolean) {
    this.yourService.updateVariable(value);
  }
}