Ionic 2-如何在调用服务以外的自定义方法中使用订阅

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

@Injectable()
export class DataService {
  private dataSubject = new Subject<any>();

  public data$ = this.dataSubject.asObservable();

  constructor() { }

  public sendData(data: any) {
    this.dataSubject.next(data);
  }
}

import { Component } from '@angular/core';
import { DataService } from './data.service';

@Component({
  selector: 'app-my-component',
  template: `
    <button (click)="customMethod()">Custom Method</button>
  `
})
export class MyComponent {
  constructor(private dataService: DataService) { }

  public customMethod() {
    this.dataService.data$.subscribe(data => {
      // 在这里处理订阅到的数据
      console.log(data);
    });
  }
}