Unable to save empty list to Django ArrayField

user_11823331 0
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I have a Django model

from django.db import models
from django.contrib.postgres.fields import ArrayField


class Website(models.Model):
    id = models.BigAutoField(primary_key=True, verbose_name='ID')
    status = models.BooleanField(default=True)
    meta = ArrayField(base_field=models.CharField(max_length=200, null=True), default=list)

I'm using following serializer to save data to the DB:

class WebsiteConfigSerializer(serializers.ModelSerializer):
    class Meta:
        model = Website
        fields = ('status', 'meta')

When I'm trying to save the following data, I'm getting error:

{
    "status": true,
    "meta": []
}

#ERROR:
# "meta : This list may not be empty."

Is it not possible to save an empty list to an ArrayField ? When I'm not passing the field at all, the value getting stored is {NULL}. Also during initial migrations, since I had added a default value as list, all my existing entries had "meta" value as {}

If the empty list value is not allowed at all, how come this got saved during initial migration ?

django-rest-framework python-3.x postgresql django-models django
2 Answers

try chaging your model to

from django.db import models
from django.contrib.postgres.fields import ArrayField


class Website(models.Model):
    id = models.BigAutoField(primary_key=True, verbose_name='ID')
    status = models.BooleanField(default=True)
    meta = ArrayField(base_field=models.CharField(max_length=200, null=True), default=list, blank=True)
user_30360580

It's possible to save an empty list, it's even a possible default as the documentation states:

If you give the field a default, ensure it’s a callable such as list (for an empty default) or a callable that returns a list (such as a function). Incorrectly using default=[] creates a mutable default that is shared between all instances of ArrayField.

However, your serializer doesn't allow empty values:

class WebsiteConfigSerializer(serializers.ModelSerializer):
    meta = serializers.ListField(
        allow_empty=True,
        child=serializers.CharField(
            max_length=200, allow_blank=True
        )
    )
    class Meta:
        model = Website
        fields = ('status', 'meta')

You can simplify this, by creating a serializer field:

from rest_framework import serializers


class ArrayField(serializers.ListField):
    child = serializers.CharField(max_length=200, allow_blank=True)

class WebsiteConfigSerializer(serializers.ModelSerializer):
    meta = ArrayField(allow_empty=True)
    class Meta:
        model = Website
        fields = ('status', 'meta')
Admin1
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