I will show two different validations, one with the validation of one attribute of the serializer and the second with the validation of different attributes.
validation of different attributes in validate():
# serializers.py
class ProjectCreateSerializer(serializers.ModelSerializer):
class Meta:
model = Project
fields = [
"id",
"name",
"description",
"project_type",
]
def validate(self, attrs):
if (
self.context["view"]
.project.filter(name=attrs["name"], project_type=attrs["project_type"])
.exists()
):
raise serializers.ValidationError("Attention! This project exists already.")
return attrs
self.context["view"].project this project property/attribute is created in view (ProjectViewSet). With this syntax we can get the project property and filter for existing projects. If this combination of name and project_type is found, the ValidationError will be raised. Otherwise the project will be validated.
validation with one attributes in validate_user():
validate_user the user part is the name of the attribute from the serializer. If you have an attribute project the function name would be validate_project().
# serializers.py
class ContributorSerializer(serializers.ModelSerializer):
# create attribute 'user', which is write_only because we just need to give a value
user = serializers.IntegerField(write_only=True)
class Meta:
model = UserModel
fields = ["id", "user"]
def validate_user(self, value):
user = UserModel.objects.filter(pk=value).first()
if user is None:
raise serializers.ValidationError("User does not exists!")
if user.is_superuser:
raise serializers.ValidationError(
"Superusers cannot be added as contributors."
)
if self.context["view"].project.contributors.filter(pk=value).exists():
raise serializers.ValidationError(
"This user is already a contributor of this project."
)
return user
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