Complete example of cursor based pagination in relay spec

[Tushant]

I am trying to implement cursor based pagination by following relay spec from the documentation. But there are two issues I am facing. First the arguments like after, before are not shown and the second one is where should I write the query. I am not blaming to documentation rather its my lack of knowledge I could not understand. Any help or support is highly appreciated. Below is the source code so far as per my understanding.

from api.query import (UserQueryType,)
query = merge_types("Query", (UserQueryType,))
strawberry.Schema(query=query, mutation=mutation)

from apps.user.query import UserQueryResolver
UserQueryType = create_type(name="UserQuery", fields=[strawberry.field(UserQueryResolver.current_user, permission_classes=[IsAuthenticated]),strawberry.field(UserQueryResolver.users),])

@strawberry.type
class UserQueryResolver:
    @strawberry.relay.connection(UserPaginated)
    async def users(self, info: Info) -> UserPaginated:
        return await service.users(info)

async def users(info: Info):
    loaders = info.context.loaders
    async with async_session() as session:
        user_ids = await session.scalars(select(User.id).filter())
        user_list = await loaders.users_id_loader.load_many(user_ids)
    # return [UserType.from_instance(user) for user in user_list]
    return user_list
    
@strawberry.type
class RelayBaseType(strawberry.relay.Node):
    id: strawberry.relay.NodeID[strawberry.ID]
    created_at: Optional[datetime.datetime] = None
    updated_at: Optional[datetime.datetime] = None

@strawberry.type
class User(RelayBaseType):
    full_name: Optional[str] = None
    username: Optional[str] = None
    user_profile: Optional["UserProfile"] = None
    
    @classmethod
    def from_instance(cls, user: Optional[UserModel]= None) -> Optional['User']:
        if user is None:
            return None
        return cls(
            id=user.id,
            full_name=user.full_name,
            username=user.username,
            created_at=user.created_at,
            updated_at=user.updated_at,
        )

    @strawberry.field
    async def user_profile(self, root) -> Optional["UserProfile"]:
        async with async_session() as session:
            return await session.scalar(    select(UserProfileModel).filter(UserProfileModel.user_id == root.id)

@strawberry.type
class UserPaginated(strawberry.relay.ListConnection[User]):
    @classmethod
    def resolve_node(cls, node: UserModel, *, info: Info, **kwargs) -> User:
        return User.from_instance(node)

I have asked this on discord as well.

[Tushant]

you can see there is no first, last, after, before arguments at all. Can anyone help me at this, please?

[Tushant]

not sure if I am following the right way but this solved me after I dug into the source code

@strawberry.type
class UserQueryResolver:
    @relay.connection(UserType)
    async def users(self, info: Info, first: Optional[int] = 10,
                    last: Optional[int] = None,
                    after: Optional[str] = None,
                    before: Optional[str] = None,) -> UserPaginated:
        return await service.users(info, first, last, after, before)


async def users(info: Info, first, last, after, before):
    loaders = info.context.loaders
    limit = min(first, last) if first and last else first or last
    async with async_session() as session:
        user_ids = await session.scalars(select(User.id).filter())
        user_list = await loaders.users_id_loader.load_many(user_ids)
    user_instances = [UserType.from_instance(user) for user in user_list]
    return UserPaginated.resolve_connection(
        user_instances,
        info=info,
        first=first,
        last=last,
        after=after,
        before=before

    )
    
@strawberry.type
class User(RelayBaseType):
    full_name: Optional[str] = None
    username: Optional[str] = None
    user_profile: Optional["UserProfile"] = None
    
    @classmethod
    def from_instance(cls, user: Optional[UserModel]= None) -> Optional['User']:
        if user is None:
            return None
        return cls(
            id=user.id,
            full_name=user.full_name,
            username=user.username,
            created_at=user.created_at,
            updated_at=user.updated_at,
        )

    @strawberry.field
    async def user_profile(self, root) -> Optional["UserProfile"]:
        async with async_session() as session:
            return await session.scalar(    select(UserProfileModel).filter(UserProfileModel.user_id == root.id)

@strawberry.type
class UserPaginated(relay.ListConnection[User]):
    @classmethod
    def resolve_connection(cls, node: List[User], info: Info, first, last, after, before, **kwargs) -> 'UserPaginated':
        return ListConnection.resolve_connection(
            node,
            info=info,
            first=first,
            last=last,
            after=after,
            before=before
        )

[eudago]

Check this pr