如何在 Graphene-Django 中传递 django-simple-history model？

Question

I have created an instance of simple_history.models.HistoricalRecords in my Notification model

models.py

class Notification(models.Model):
    title = models.CharField(max_length=500)
    content = RichTextField()
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    history = HistoricalRecords()


class Attachment(models.Model):
    title = models.CharField(max_length=500)
    attachement = models.FileField(upload_to = user_directory_path)
    notifiaction = models.ForeignKey(Notification, on_delete=models.SET_NULL, null= True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

schema.py

class AttachmentNode(DjangoObjectType):
    class Meta:
        model = Attachment
        filter_fields = ['title']
        interfaces = (relay.Node, )


class NotificationNode(DjangoObjectType):
    class Meta:
        model = Notification
        filter_fields = {
            'id': ['exact'],
            'title': ['exact', 'icontains', 'istartswith'],
        }
        interfaces = (relay.Node, )



class Query(graphene.ObjectType):
    notifications = relay.Node.Field(NotificationNode)
    all_notifications = DjangoFilterConnectionField(NotificationNode)

This is working fine but I want all the records created by the HistoricalRecords() for the notification model in the graphql endpoint when I query the notification. How can I do this?

Answer 1

I assume you want each notification's history inside it, probably to show it somewhere in your app.

Getting a change list from a list of revisions

Looks like there's an issue you'll have to solve first - django-simple-history stores revisions of objects, and not the diffs. You'll have figure out a way to convert this

[
    <HistoricalNotification: Notification object as of 2010-10-25 18:04:13.814128>,
    <HistoricalNotification: Notification object as of 2010-10-25 18:03:29.855689>,
]

to something like this by comparing adjacent revisions and finding the differences:

[
    "Created by Jack Pear 10 minutes ago",
    "title changed by Jack Pear 8 minutes ago",
]

In reality you probably need dicts instead of stings, so it's easier to process on frontend.

There is a tool included in django-simple-history just for that. Here's some pseudocode of how you might do it:

class Notification(models.Model):
    title = models.CharField(max_length=500)
    content = RichTextField()
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    history = HistoricalRecords()

    def get_changelist(self):
        record = self.history.first()
        while record.next_record:
            delta = record.diff_against(record.next_record)
            for change in delta.changes:
                yield {
                    "field": change.field,
                    "old": change.old,
                    "new": change.new,
                    "changed_by": record.next_record.history_user,
                    "changed_at": record.next_record.history_date,
                }
            record = record.next_record

Adding the changelist to graphql

We'll have to declare a separate ObjectType for changelist objects:

class ChangeListItemNode(graphene.ObjectType):
    field = graphene.ID()
    old = graphene.ID()
    new = graphene.ID()
    changed_by = graphene.Field(UserNode)
    changed_at = graphene.DateTime()

After that, we declare a custom field with a resolver on NotificationNode :

class NotificationNode(DjangoObjectType):
    changelist = graphene.List(ChangeListItemNode)

    class Meta:
        model = Notification
        filter_fields = {
            'id': ['exact'],
            'title': ['exact', 'icontains', 'istartswith'],
        }
        interfaces = (relay.Node, )

    @staticmethod
    def resolve_changelist(notification, info, **kwargs):
        return notification.get_changelist()

Keep in mind that this was not tested, it's just pseudocode and definitely contains bugs. This should provide a starting point though.