title: Django, POST method, already logged in user
body: <p>I write an app in django - sth like twitter, i have already log in/log out panel, and form when already logged in user can add a tweet. 
  A tweet has a 3 columns in database: </p>
  
  <pre><code>class Tweet(models.Model):
      content = models.CharField(max_length=140)
      creation_date = models.DateTimeField(auto_now_add=True)
      user = models.ForeignKey(User, on_delete=models.CASCADE)
  </code></pre>
  
  <p>The form looks like:</p>
  
  <pre><code>class TweetForm(forms.Form):
      content = forms.CharField(label='content')
  </code></pre>
  
  <p>And the view:</p>
  
  <pre><code>class TweetCreationView(LoginRequiredMixin, View):
      permission_required = 'twitter.add_tweet'
      raise_exception = True
      permission_denied_message = 'You are not allowed being there!'
  
      def get(self, request):
          form = TweetForm()
          return render(request, "twitter/add_tweet.html", {"form": form})
  
      def post(self, request):
          form = TweetForm(request.POST)
          if form.is_valid():
              if request.user.is_authenticated():
                  username = request.user.username
                  user_id = username.id
                  content = form.cleaned_data.get('content')
          return render(request, "twitter/add_tweet.html", {"form": form})
  </code></pre>
  
  <p>How can i obtain an already logged in user in django and add his/her id to post view form?</p>