如何在angular的不同环境下检查特征是否为真？

import { MediaObserver } from '@angular/flex-layout';

constructor(private mediaObserver: MediaObserver) { }

const isFeatureTrue = this.mediaObserver.isActive('特征媒体查询');

import { Component } from '@angular/core';
import { MediaObserver } from '@angular/flex-layout';

@Component({
  selector: 'app-my-component',
  template: `
    <div *ngIf="isFeatureTrue">特征为真</div>
    <div *ngIf="!isFeatureTrue">特征为假</div>
  `
})
export class MyComponent {
  isFeatureTrue: boolean;

  constructor(private mediaObserver: MediaObserver) {
    this.isFeatureTrue = this.mediaObserver.isActive('特征媒体查询');
  }
}