title: Global Service - getting value is undefined
body: <blockquote>
    <p><code>"@angular/common": "^5.0.0"</code></p>
  </blockquote>
  
  <p>I searched a lot about it and most say to do it that way ... What am I doing wrong?</p>
  
  <p>My intuition says that every time that I build (constructor) another component, the GlobalService will be clean, but I don't know how to do this correctly...</p>
  
  <p><strong>GlobalService</strong></p>
  
  <pre><code>import { Injectable } from '@angular/core';
  
  @Injectable()
  export class GlobalService{
    private currency;
    constructor() {
     }
    setCurrency(val) {
        this.currency = val;
    }
    getCurrency() {
        return this.currency;
    }
  }
  </code></pre>
  
  <p><strong>GlobalService Module</strong></p>
  
  <pre><code>@NgModule({
    ...,
    providers:[ GlobalService ]
  })
  </code></pre>
  
  <p><strong>Setting Value (Any Component)</strong></p>
  
  <pre><code>import { GlobalService } from '.path/global.service';
  
  constructor(..., private global: GlobalService) { }
  
  anyMethod(){
    this.global.setCurrency('Test Global Service');
    console.log(this.global.getCurrency()); // On console =&gt; Test Global Service
  }
  </code></pre>
  
  <p><strong>Getting Value (Another Any Component)</strong></p>
  
  <pre><code>import { GlobalService } from '.path/global.service';
  
  constructor(..., private global: GlobalService) { }
  
  anyMethod(){
    console.log(this.global.getCurrency()); // On console =&gt; undefined
  }
  </code></pre>