DRF Serializer error, "Incorrect type. Expected pk value, received str."

Using Django Forms & APIs
1

I’ve got a serializer to update a model which has got a field -

used_toys = ListField(child=PrimaryKeyRelatedField(queryset=Toys.objects.all()), required=False)

I am also using OpenAPI for documentation.
The problem is when I add values to that field on Swagger UI and execute, I got this error for array fields.

"used_toys": {
    "0": [
      "Incorrect type. Expected pk value, received str."
    ]
  }

Here’s the curl cmd

curl -X PATCH "http://0.0.0.0:8000/api/toys/update/" -H "accept: application/json" -H "Content-Type: multipart/form-data" -H "X-CSRFToken: k8OYLRtWnUD8CIi6uhLT83xG4HcM52JECc24tT8b19AwzMFFFZZsRK0yz5MBRX46" -d {"used_toys":"\"15\",\"3\""}

I am not sure what is wrong and what I should fix
Any help would be appreciated.

2

Since you’re supposed to be sending a list of integers, have you tried sending either '{"used_toys": [15, 3]}' or '{"used_toys": ["15", "3"]}'? (enclosing the entire string in single quotes avoids the need of escaping the double-quote characters)

3

Thanks, @KenWhitesell
Yes, I think so.
But the problem is I am using Swagger and I am not sure how to convert it as you suggested in Swagger.
I think the API would work fine on other client apps because they will make send the data in correct form.

4

I’m not familiar with swagger, but is it worth confirming that this would work with curl?

5

A quick glance through the OpenAPI Specification gives me the impression that specifying the field as of type array should produce the desired results. How do you have “used_toys” defined?

6

This one

used_toys = ListField(child=PrimaryKeyRelatedField(queryset=Toys.objects.all()), required=False)

Would you please send me the link to that OpenAPI Specification?

7

Yes, I saw how that’s what you have defined in your code - I’m looking for the OpenAPI definition for the field.

and…
https://swagger.io/specification/

8

Hi, @KenWhitesell

I finally resolved this issue by overriding ModelSerializer’s to_internal_value and update method.
I added my own preprocessing to convert that weird string literal into a valid list.

Thanks for your help

9

Hii @devspectre could you please share the steps on how you solved the problem?

I am trying to pass a list of student IDs but it is not working.
Below is the to_internal_value method which I have overridden.

def to_internal_value(self, data):
    tempdict = data.copy()
    tempdict['students'] = json.loads(data['students'])
    data = tempdict
    return super(NoticesSerializer, self).to_internal_value(data)

but it always returns the same error

{students: [“Incorrect type. Expected pk value, received list.”]}

10

@Vishalpandey1247
It’s saying it received list.

What is your payload look like on client side?

How do you make the requests?
Swagger, Postman or Insomnia?