Add a Custom Action to Django Admin and Remove the Restriction of Having to Select Objects

Introduction

I have to say, Django's Admin really brings a lot of convenience to development. Here I am tinkering again, this time adding a custom action.

You can check the official documentation for this custom Action; it's very detailed, so I won't repeat it.

https://docs.djangoproject.com/en/3.0/ref/contrib/admin/actions/

UI Effect

By default, after adding an action in Django, you have to select objects below before you can submit. But I don't need that—I just want to simply click Start Lottery and have the prize drawn right away. Persistence pays off; I still found a solution on Stack Overflow, (SOF-oriented programming, as expected)

Next, I'll explain how to implement it~

Define the Action

Write the following code in admin.py:

@admin.register(models.PrizeLog)
class PrizeLogAdmin(admin.ModelAdmin):
    actions = ['draw_prize']

    def draw_prize(self, request, queryset):
        pass

    draw_prize.short_description = '开始抽奖'
    draw_prize.type = 'warning'
    draw_prize.confirm = '确认即开始抽奖并发送中奖通知~'

This will display the button, but clicking it still won't execute the code inside the draw_prize method, because Django requires at least one object to be selected before an action can run.

Next, we'll take a roundabout approach to bypass this restriction.

Remove the Restriction

Still in this Admin class, write the following code:

@admin.register(models.PrizeJoinLog)
class PrizeJoinLogAdmin(admin.ModelAdmin):
    actions = ['draw_prize']

    def changelist_view(self, request, extra_context=None):
        try:
            action = self.get_actions(request)[request.POST['action']][0]
            action_acts_on_all = action.acts_on_all
        except (KeyError, AttributeError):
            action_acts_on_all = False

        if action_acts_on_all:
            post = request.POST.copy()
            post.setlist(admin.helpers.ACTION_CHECKBOX_NAME,
                         self.model.objects.values_list('id', flat=True))
            request.POST = post

        return super(PrizeJoinLogAdmin, self).changelist_view(request, extra_context)

    def draw_prize(self, request, queryset):
        pass

    draw_prize.short_description = '开始抽奖'
    draw_prize.type = 'warning'
    draw_prize.confirm = '确认即开始抽奖并发送中奖通知~'
    draw_prize.acts_on_all = True

Note the code above: we added the changelist_view method, and in the last line we added an acts_on_all attribute to draw_prize and set it to True (that's the invincible dynamic language Python for you)

This way, when submitting, changelist_view detects that the action has an acts_on_all attribute and automatically includes all objects—equivalent to automatically checking all objects for us. Pretty neat~

Discussion Welcome

This approach doesn't feel entirely perfect though. If you experts have a better solution, feel free to leave a comment and discuss~

References

• https://stackoverflow.com/questions/4500924/django-admin-action-without-selecting-objects
• https://simpleui.88cto.com/docs/simpleui/QUICK.html#%E8%87%AA%E5%AE%9A%E4%B9%89%E6%8C%89%E9%92%AE-action

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