Cannot cache component - cannot pickle 'generator' object

[hamidrabedi]

I have this list view that requires pagination and i have a generator for paginating but i keep getting this warning:

Cannot cache component '<class 'pages.components.multimedia_list.MultimediaListView'>' because it is not picklable: <class 'TypeError'>: cannot pickle 'generator' object

This is the code:

from django.db.models import QuerySet
from django.core.paginator import Paginator

from django_unicorn.components import UnicornView

from pages.models import MultiMedia


class MultimediaListView(UnicornView):
    multimedia: QuerySet[MultiMedia] = None
    items = None
    items_per_page = 6  # Number of items to display per page
    page_index = 1  # Current page index
    paginator = None  # Paginator object
    page = None  # Current page
    page_range = None  # Range of pages to display

    class Meta:
        """
        Meta class for additional settings.
        """
        javascript_exclude = (
            "paginator",
            "page",
            "page_range",
            "multimedia",
        )  # Fields to exclude from JavaScript

    def mount(self):
        """
        Prepares the view for rendering.
        """
        self.paginate()

    def paginate(self):
        """
        Paginates the multimedia based on the current page index and items per page.
        """
        paginator = Paginator(self.multimedia, self.items_per_page)
        self.paginator = paginator
        self.page = self.paginator.page(self.page_index)
        self.page_range = self.paginator.get_elided_page_range(number=self.page_index, on_each_side=3, on_ends=2)
        self.items = self.page.object_list

    def go_to_page(self, page):
        """
        Changes the current page to the specified page and paginates the multimedia.
        """
        self.page_index = page
        self.page = ''
        self.paginate()

Which page_range is the generator object, is there anyway to fix this?
and why pickling and caching all the attributes is necessary? like why should it be done?

[hoshmandent]

Hello,

The issue you're encountering is because Django Unicorn needs to serialize (pickle) the component state, but the get_elided_page_range() method returns a generator object which can't be pickled. Here's a solution that addresses this by creating serializable versions of the pagination objects:

from django.core.paginator import Page, Paginator
from django_unicorn.components import UnicornView

class SerializablePaginator:
    """A JSON-serializable version of Django's Paginator"""
    def __init__(self, paginator):
        self.num_pages = paginator.num_pages
        self.count = paginator.count
        self.ELLIPSIS = paginator.ELLIPSIS
        self._elided_page_range = None

    def get_elided_page_range(self, **kwargs):
        """Return the elided page range if it was set"""
        return self._elided_page_range if self._elided_page_range is not None else []

class SerializablePage:
    """A JSON-serializable version of Django's Page object"""
    def __init__(self, page_obj):
        self.object_list = list(page_obj.object_list)
        self.number = page_obj.number
        self.has_next = page_obj.has_next()
        self.has_previous = page_obj.has_previous()
        self.next_page_number = page_obj.next_page_number() if page_obj.has_next() else None
        self.previous_page_number = page_obj.previous_page_number() if page_obj.has_previous() else None
        
        # Store paginator and convert elided page range to list
        self.paginator = SerializablePaginator(page_obj.paginator)
        self.paginator._elided_page_range = list(page_obj.paginator.get_elided_page_range(
            number=page_obj.number,
            on_each_side=1,
            on_ends=1
        ))

# Example usage in your view
class MultimediaListView(UnicornView):
    items_per_page = 6
    page_index = 1
    
    def paginate(self):
        paginator = Paginator(self.multimedia, self.items_per_page)
        page_obj = paginator.page(self.page_index)
        # Convert to serializable format
        self.page = SerializablePage(page_obj)
        self.items = self.page.object_list

The key changes are:

1. Create serializable wrapper classes for both Paginator and Page objects
2. Convert the generator from get_elided_page_range() to a list during initialization
3. Store only the necessary pagination data in a format that can be pickled

This solution maintains all the pagination functionality while making it compatible with Django Unicorn's component state serialization.