Service variable when passing data from one component to another angular 2

I am trying to pass a variable from one component to another. I am doing that by using a service:

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


    @Injectable()
    export class SharedService {
      // private questionNumber = new Subject<number>();
      // questionNumber$ = this.questionNumber.asObservable();
      questionNumber : number;
      publishData(number:number) {
        this.questionNumber = number;
        console.log(this.questionNumber,'publish');
      }

  getQuestionData(){
    console.log(this.questionNumber,'get');
    return this.questionNumber;
  }

  constructor() { }

}

If the data gets changed in the function "publishData" it writes the current variable value in the console:

But if I try to access that variable it is still undefined as if it isn't changed

Component 1 (excerpt) :

import { Component, OnInit } from '@angular/core';
import { ViewEncapsulation } from '@angular/core';
import { SharedService } from '../shared.service';

@Component({
  selector: 'app-main-quiz',
  templateUrl: './main-quiz.component.html',
  styleUrls: ['./main-quiz.component.css'],
  encapsulation: ViewEncapsulation.None,
  providers: [SharedService]
})
export class MainQuizComponent implements OnInit {

  constructor(private _sharedService: SharedService){
    this._sharedService = _sharedService;
  }

  updateQuestion(){
    this._sharedService.publishData(this.questionNumber);
  };

Component 2:

import { Component, OnInit, Input } from '@angular/core';
import { ViewEncapsulation } from '@angular/core';
import { SharedService } from '../shared.service';

@Component({
  selector: 'app-win-page',
  templateUrl: './win-page.component.html',
  styleUrls: ['./win-page.component.css'],
  encapsulation: ViewEncapsulation.None,
  inputs: ['questionNumber'],
  providers: [SharedService]
})
export class WinPageComponent implements OnInit {

  constructor(private _sharedService : SharedService) {
    this._sharedService = _sharedService;
    this.questionNumber = this._sharedService.getQuestionData();
   }

  questionNumber : number;

  ngOnInit() {

  }

  ngOnChanges(){
    this.questionNumber = this._sharedService.getQuestionData();
  }

}

Why isn't that variable updated ?

Thanks for your help!