Django Rest Framework many to many with extra fields serialization

Question

 class Item(models.Model):
 name = models.CharField(max_length=20)

 class Meals(models.Model):
 name = models.CharField(max_length=50)
 ingredients = models.ManyToManyField(Item, through='MealRecipe')


 class Menu(models.Model):
 name = models.CharField(max_length=50)
 meals = models.ManyToManyField(Meals,through='CompMenu')


 class CompMenu(models.Model):
 TYPE_COMP = (
     ('B', 'Breakfast'),
     ('L', 'Lunch'),
     ('D', 'Dinner')
 )
 menu = models.ForeignKey(Menu)
 meal = models.ForeignKey(Meals)
 type = models.CharField(max_length=1, choices=TYPE_COMP)

 class MealRecipe(models.Model):
 meal = models.ForeignKey(Meal)
 item = models.ForeignKey(Item)
 qty = models.IntegerField()

If i need to serialze queryset how can i do it, there is no documentation about it, i need a JSON with Item_id, Item_name, MealRecipe_qty. Do i have to serialze all models ? I need this to manipualte the recipe quantities on the front end based on the selected menu.

 receipes = MealRecipe.objects.filter(meal__in=meals_of_menu)
 for receipe in receipes:
 name = receipe.item.name
 qty = receipe.qty

OR

 MealRecipe.objects.filter(meal__menu=some_menu_instance).distinct()

I cannot figure out how to pass the result o this query to the front end

Aniruddha Bhondwe · Accepted Answer · 2017-03-09 05:38:22Z

3

For your requirements of Item_id, Item_name, MealRecipe_qty, you will need to serialize the MealRecipe model and the Item model.

Also give a related name to item in MealRecipe model

class MealRecipe(models.Model):
    meal = models.ForeignKey(Meal)
    item = models.ForeignKey(Item,related_name='qty')
    qty = models.IntegerField()

And your serializers will be

class MealRecipeSerializer(serializers.ModelSerializer):

    class Meta:
        model = MealRecipe
        fields = ('qty')

class ItemSerializer(serializers.ModelSerializer):

    qty = MealRecipeSerializer()
    class Meta:
        model = Item
        fields = ('id','name','qty')

Also if you are passing a queryset to a serializer do it as, MealRecipeSerializer(many=True)

edited Mar 9, 2017 at 5:38

answered Mar 9, 2017 at 5:32

Aniruddha Bhondwe

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2 Comments

gaccep Over a year ago

It worked, but i used MealRecipe.objects.all(), can i use MealRecipe.objects.filter(meal__menu=some_menu_instance).distinct() result as the queryset for my serializer?

Aniruddha Bhondwe Over a year ago

Should work. If the query provides a queryset of MealRecipe objects it should work.

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