title: Angular 6 Updating Observable
body: <p>Hi i'am new to Angular 6 and can't make things work after several researching.
  I have a list coming from jsonplaceholder.typecode.com and as i have read its docs, I can post, delete, and update but how can i make my list change async'ly as i perform those methods.</p>
  
  <p>this are my methods from a service</p>
  
  <pre><code>getContacts(){
  return this.contact = 
   this.http.get('https://jsonplaceholder.typicode.com/users');
  }
  
  getUser(id){
   return this.http.get('https://jsonplaceholder.typicode.com/users/'+id);
  }
  
  addContact(newContact: Contact){
   return this.http.post('https://jsonplaceholder.typicode.com/users', 
  newContact);
   }
  
   removeContact(contact){
    return 
   this.http.delete('https://jsonplaceholder.typicode.com/users/'+contact.id);
  }
  
  updateContact(contac: Contact){
  return 
  this.http.put('https://jsonplaceholder.typicode.com/users/'+contac.id, 
   contac);
   } 
  </code></pre>