Angular 7.如何从另一个页面(dashboard.page.ts-in.page.ts)控制页面上的变量

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

@Injectable({
  providedIn: 'root'
})
export class SharedService {
  public variable: any;

  constructor() { }
}

import { Component } from '@angular/core';
import { SharedService } from 'path/to/shared.service';

@Component({
  selector: 'app-dashboard',
  templateUrl: 'dashboard.page.html',
  styleUrls: ['dashboard.page.scss'],
})
export class DashboardPage {
  constructor(private sharedService: SharedService) {}

  updateVariable() {
    this.sharedService.variable = 'New value';
  }
}

import { Component } from '@angular/core';
import { SharedService } from 'path/to/shared.service';

@Component({
  selector: 'app-in',
  templateUrl: 'in.page.html',
  styleUrls: ['in.page.scss'],
})
export class InPage {
  constructor(private sharedService: SharedService) {}

  getVariable() {
    console.log(this.sharedService.variable);
  }
}