# Τεκμηρίωση του Django - 1.10.7

# Admin actions

The basic workflow of Django’s admin is, in a nutshell, “select an object, then change it.” This works well for a majority of use cases. However, if you need to make the same change to many objects at once, this workflow can be quite tedious.

In these cases, Django’s admin lets you write and register “actions” – simple functions that get called with a list of objects selected on the change list page.

If you look at any change list in the admin, you’ll see this feature in action; Django ships with a “delete selected objects” action available to all models. For example, here’s the user module from Django’s built-in `django.contrib.auth` app:

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The “delete selected objects” action uses `QuerySet.delete()` for efficiency reasons, which has an important caveat: your model’s `delete()` method will not be called.

If you wish to override this behavior, simply write a custom action which accomplishes deletion in your preferred manner – for example, by calling `Model.delete()` for each of the selected items.

For more background on bulk deletion, see the documentation on object deletion.

Read on to find out how to add your own actions to this list.

## Writing actions

The easiest way to explain actions is by example, so let’s dive in.

A common use case for admin actions is the bulk updating of a model. Imagine a simple news application with an `Article` model:

    from django.db import models

    STATUS_CHOICES = (
        ('d', 'Draft'),
        ('p', 'Published'),
        ('w', 'Withdrawn'),
    )

    class Article(models.Model):
        title = models.CharField(max_length=100)
        body = models.TextField()
        status = models.CharField(max_length=1, choices=STATUS_CHOICES)

        def __str__(self):              # __unicode__ on Python 2
            return self.title

A common task we might perform with a model like this is to update an article’s status from “draft” to “published”. We could easily do this in the admin one article at a time, but if we wanted to bulk-publish a group of articles, it’d be tedious. So, let’s write an action that lets us change an article’s status to “published.”

### Writing action functions

First, we’ll need to write a function that gets called when the action is triggered from the admin. Action functions are just regular functions that take three arguments:

- The current `ModelAdmin`
- An `HttpRequest` representing the current request,
- A `QuerySet` containing the set of objects selected by the user.

Our publish-these-articles function won’t need the `ModelAdmin` or the request object, but we will use the queryset:

    def make_published(modeladmin, request, queryset):
        queryset.update(status='p')

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For the best performance, we’re using the queryset’s update method. Other types of actions might need to deal with each object individually; in these cases we’d just iterate over the queryset:

    for obj in queryset:
        do_something_with(obj)

That’s actually all there is to writing an action! However, we’ll take one more optional-but-useful step and give the action a “nice” title in the admin. By default, this action would appear in the action list as “Make published” – the function name, with underscores replaced by spaces. That’s fine, but we can provide a better, more human-friendly name by giving the `make_published` function a `short_description` attribute:

    def make_published(modeladmin, request, queryset):
        queryset.update(status='p')
    make_published.short_description = "Mark selected stories as published"

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This might look familiar; the admin’s `list_display` option uses the same technique to provide human-readable descriptions for callback functions registered there, too.

### Adding actions to the `ModelAdmin`

Next, we’ll need to inform our `ModelAdmin` of the action. This works just like any other configuration option. So, the complete `admin.py` with the action and its registration would look like:

    from django.contrib import admin
    from myapp.models import Article

    def make_published(modeladmin, request, queryset):
        queryset.update(status='p')
    make_published.short_description = "Mark selected stories as published"

    class ArticleAdmin(admin.ModelAdmin):
        list_display = ['title', 'status']
        ordering = ['title']
        actions = [make_published]

    admin.site.register(Article, ArticleAdmin)

That code will give us an admin change list that looks something like this:

That’s really all there is to it! If you’re itching to write your own actions, you now know enough to get started. The rest of this document just covers more advanced techniques.

### Handling errors in actions

If there are foreseeable error conditions that may occur while running your action, you should gracefully inform the user of the problem. This means handling exceptions and using `django.contrib.admin.ModelAdmin.message_user()` to display a user friendly description of the problem in the response.

## Advanced action techniques

There’s a couple of extra options and possibilities you can exploit for more advanced options.

### Actions as `ModelAdmin` methods

The example above shows the `make_published` action defined as a simple function. That’s perfectly fine, but it’s not perfect from a code design point of view: since the action is tightly coupled to the `Article` object, it makes sense to hook the action to the `ArticleAdmin` object itself.

That’s easy enough to do:

    class ArticleAdmin(admin.ModelAdmin):
        ...

        actions = ['make_published']

        def make_published(self, request, queryset):
            queryset.update(status='p')
        make_published.short_description = "Mark selected stories as published"

Notice first that we’ve moved `make_published` into a method and renamed the `modeladmin` parameter to `self`, and second that we’ve now put the string `'make_published'` in `actions` instead of a direct function reference. This tells the `ModelAdmin` to look up the action as a method.

Defining actions as methods gives the action more straightforward, idiomatic access to the `ModelAdmin` itself, allowing the action to call any of the methods provided by the admin.

For example, we can use `self` to flash a message to the user informing her that the action was successful:

    class ArticleAdmin(admin.ModelAdmin):
        ...

        def make_published(self, request, queryset):
            rows_updated = queryset.update(status='p')
            if rows_updated == 1:
                message_bit = "1 story was"
            else:
                message_bit = "%s stories were" % rows_updated
            self.message_user(request, "%s successfully marked as published." % message_bit)

This make the action match what the admin itself does after successfully performing an action:

### Actions that provide intermediate pages

By default, after an action is performed the user is simply redirected back to the original change list page. However, some actions, especially more complex ones, will need to return intermediate pages. For example, the built-in delete action asks for confirmation before deleting the selected objects.

To provide an intermediary page, simply return an `HttpResponse` (or subclass) from your action. For example, you might write a simple export function that uses Django’s serialization functions to dump some selected objects as JSON:

    from django.http import HttpResponse
    from django.core import serializers

    def export_as_json(modeladmin, request, queryset):
        response = HttpResponse(content_type="application/json")
        serializers.serialize("json", queryset, stream=response)
        return response

Generally, something like the above isn’t considered a great idea. Most of the time, the best practice will be to return an `HttpResponseRedirect` and redirect the user to a view you’ve written, passing the list of selected objects in the GET query string. This allows you to provide complex interaction logic on the intermediary pages. For example, if you wanted to provide a more complete export function, you’d want to let the user choose a format, and possibly a list of fields to include in the export. The best thing to do would be to write a small action that simply redirects to your custom export view:

    from django.contrib import admin
    from django.contrib.contenttypes.models import ContentType
    from django.http import HttpResponseRedirect

    def export_selected_objects(modeladmin, request, queryset):
        selected = request.POST.getlist(admin.ACTION_CHECKBOX_NAME)
        ct = ContentType.objects.get_for_model(queryset.model)
        return HttpResponseRedirect("/export/?ct=%s&ids=%s" % (ct.pk, ",".join(selected)))

As you can see, the action is the simple part; all the complex logic would belong in your export view. This would need to deal with objects of any type, hence the business with the `ContentType`.

Writing this view is left as an exercise to the reader.

### Making actions available site-wide

`AdminSite.``add_action`(action, name=None)

  Some actions are best if they’re made available to any object in the admin site – the export action defined above would be a good candidate. You can make an action globally available using `AdminSite.add_action()`. For example:

      from django.contrib import admin

      admin.site.add_action(export_selected_objects)

  This makes the `export_selected_objects` action globally available as an action named “export_selected_objects”. You can explicitly give the action a name – good if you later want to programmatically remove the action – by passing a second argument to `AdminSite.add_action()`:

      admin.site.add_action(export_selected_objects, 'export_selected')

### Disabling actions

Sometimes you need to disable certain actions – especially those registered site-wide – for particular objects. There’s a few ways you can disable actions:

#### Disabling a site-wide action

`AdminSite.``disable_action`(name)

  If you need to disable a site-wide action you can call `AdminSite.disable_action()`.

  For example, you can use this method to remove the built-in “delete selected objects” action:

      admin.site.disable_action('delete_selected')

  Once you’ve done the above, that action will no longer be available site-wide.

  If, however, you need to re-enable a globally-disabled action for one particular model, simply list it explicitly in your `ModelAdmin.actions` list:

      # Globally disable delete selected
      admin.site.disable_action('delete_selected')

      # This ModelAdmin will not have delete_selected available
      class SomeModelAdmin(admin.ModelAdmin):
          actions = ['some_other_action']
          ...

      # This one will
      class AnotherModelAdmin(admin.ModelAdmin):
          actions = ['delete_selected', 'a_third_action']
          ...

#### Disabling all actions for a particular `ModelAdmin`

If you want no bulk actions available for a given `ModelAdmin`, simply set `ModelAdmin.actions` to `None`:

    class MyModelAdmin(admin.ModelAdmin):
        actions = None

This tells the `ModelAdmin` to not display or allow any actions, including any site-wide actions.

#### Conditionally enabling or disabling actions

`ModelAdmin.``get_actions`(request)

  Finally, you can conditionally enable or disable actions on a per-request (and hence per-user basis) by overriding `ModelAdmin.get_actions()`.

  This returns a dictionary of actions allowed. The keys are action names, and the values are `(function, name, short_description)` tuples.

  Most of the time you’ll use this method to conditionally remove actions from the list gathered by the superclass. For example, if I only wanted users whose names begin with ‘J’ to be able to delete objects in bulk, I could do the following:

      class MyModelAdmin(admin.ModelAdmin):
          ...

          def get_actions(self, request):
              actions = super(MyModelAdmin, self).get_actions(request)
              if request.user.username[0].upper() != 'J':
                  if 'delete_selected' in actions:
                      del actions['delete_selected']
              return actions