Save belongs to relation in database

[Amit Singh]

My Table structure is there are four tables

user
coin
exchange

their reference goes to

user_exchange_plan

with keys

user_id, coin_id, exchange_id

so i am creating a user exchange plan via api
for this i am sending a request like




{ "user": 1, "coin": 1, "exchange": 1, "plan_type": null, ..... }

but it is throwing validation error that all three are required. what could i be possibly doing wrong.
how can i save foreign keys in this record.

Following is the code for my serializer

`class UserTradePlanSerializer(serializers.ModelSerializer):

#code1
user = serializers.PrimaryKeyRelatedField(queryset=SUser.objects.all())
coin = serializers.PrimaryKeyRelatedField(queryset=Coin.objects.all())
exchange = serializers.PrimaryKeyRelatedField(queryset=Exchange.objects.all())

 #code2
# user = SUserSerializer()
# coin = CoinSerializer()
# exchange = ExchangeSerializer()

def create(self, validated_data):
    return UserTradePlan.objects.create(**validated_data)

class Meta:
    model = UserTradePlan
    fields = ("id", "user", "coin", "exchange", "plan_type", ....)
    depth = 1`

if i activate the code written under #code1 then it will work as expected, but while retrieving it will not replace user with user object. it will return the id of that user plain.

if i activate the code written under #code2 and comment the code #code1 then while retrieving it replaces the user with object but it start throwing the validation error.

what is the appropriate way to save and retrieve the values of association table. So that when saved it saves the id and when retrieved it replaces it by object. i haven't used user_id field do i need to add it to send the value?

thanks

[Ryoma Han]

Sorry, I'm not sure if my understanding is correct.

In my view, you have user coin exchange and user_exchange_plan , four models , like:

class User(models.Model):
    ...

class Coin(models.Model):
    ...

class Exchange(models.Model):
    ...

class UserExchangePlan(models.Model):
    user = ForeignKey(User, ...)
    coin = ForeignKey(Coin, ...)
    exchange =ForeignKey(Exchange, ...)

now you want to create a user_exchange_plan with user_id coin_id exchange_id

just create your UserExchangePlanSerializers like:

class UserExchangePlanSerializers(ModelSerializer):

    class Meta:
        model = UserExchangePlan
        fields = '__all__'

create your UserExchangePlanViewSet like:

class UserExchangePlanViewSet(ModelViewSet):
    queryset = UserExchangePlan.objects.all()
    serializer = UserExchangePlanSerializers

you can post {"user": <id>, "coin": <id>, "exchange": <id>,...} to create a user_exchange_plan database data

if you want to list user_exchange_plan's user coin exchange with list data type, you just need to create a new user_exchange_plan serializer like:

class ListUserExchangePlan(ModelSerializer):
    user = YourUserSerializer()
    coin = YourCoinSerializer()
    exchange = YourExchangeSerializer()

    class Meta:
        model = UserExchangePlan
        fields = '__all__'

You can build new YourUserSerializer/YourCoinSerializer/YourExchangeSerializer to your needs.

I hope my understanding is correct.

If you have other questions, you can email me directly.

By RyomaHan

 2019年5月7日星期二 UTC+8下午8:47:51，Amit Singh写道：