title: DRF oneToOneField Create Serializer
body: <p>trying to do some nested model creation with drf/create serizlizer.</p>
  
  <p>what i'm trying to serialize is 'TradePost' model, which has post, and ProductItem in it.</p>
  
  <p>i already have 'ProductItemSerializer', and 'PostSerializer' by using this.. how can i serialize them?? with creation? not by telling existing record with pk value.</p>
  
  <p>models.py</p>
  
  <pre><code>class ProductItem(models.Model):
      baseProduct = models.ForeignKey(Product, related_name='baseProduct')
  
      seller = models.ForeignKey(User)
  
      price = models.DecimalField(max_digits=6, decimal_places=2)
  
      isOrderClosed = models.BooleanField()
      isTradeCompleted = models.BooleanField()
  
  
      def __str__(self):
          return '[seller = '+self.seller.username+']' + '[product = '+(str)(self.baseProduct)+']' + '[id = '+(str)(self.id)+']'
  
  
  
  
  class TradePost(models.Model):
  
      basePost = models.OneToOneField(Post)
  
      baseProductItem = models.OneToOneField(ProductItem)
  
      def __str__(self):
          return '[post = ' + (str)(self.basePost) + ']' + '[product = ' + (str)(self.baseProductItem) + ']' + '[id = ' + (str)(self.id) + ']'
  </code></pre>
  
  <p>in serialziers.py</p>
  
  <pre><code>class ProductItemCreateSerializer(serializers.ModelSerializer):
      class Meta:
          model = ProductItem
          fields = ('baseProduct', 'price')
  
  
  
  #???
  class TradePostCreateSerializer(serializers.ModelSerializer):
  
      class Meta:
          model = TradePost
          fields = ('basePost', 'baseProductItem',)
  
      def create(self, validated_data):
          post =
  </code></pre>