title: Saving data to the database after signup
body: <p>I'm trying to create a database with firebase after a user is signed up.
  I have this method:</p>
  
  <pre><code>writeUserData(mUID, mNickname){
      console.log("WRITE");
      firebaseRef.database().ref('users/' + mUID + '/').set({
        nickname: mNickname,
      });
  }
  </code></pre>
  
  <p>From my understanding, my database should look something like that (after this method runs):</p>
  
  <pre><code>{
   users:{
       UID:{
         nickname
       }
    }
  }
  </code></pre>
  
  <p>but after running this method, my database still null. Should I create a file or should it be created automatically after .set() happens?</p>
  
  <p>I really got confused with Firebase and hope you guys could help me somehow.</p>