2026年版 Django Admin カスタマイズ完全ガイド：アクション、フィルター、面接対策

# admin.py
from django.contrib import admin
from django.utils.html import format_html
from .models import Article


class ArticleAdmin(admin.ModelAdmin):
    list_display = ["title", "author_name", "status", "publish_date", "is_recent"]
    search_fields = ["title", "author__email", "content"]
    list_per_page = 50
    list_select_related = ["author"]  # N+1クエリを回避

    @admin.display(description="著者", ordering="author__last_name")
    def author_name(self, obj):
        return f"{obj.author.first_name} {obj.author.last_name}"

    @admin.display(description="最近？", boolean=True)
    def is_recent(self, obj):
        from django.utils import timezone
        return obj.publish_date >= timezone.now() - timezone.timedelta(days=7)


admin.site.register(Article, ArticleAdmin)

# admin.py
from datetime import date, timedelta
from django.contrib import admin
from django.utils.translation import gettext_lazy as _
from .models import Article


class PublishDateFilter(admin.SimpleListFilter):
    title = _("公開期間")
    parameter_name = "published"  # URLパラメータ: ?published=this_week

    def lookups(self, request, model_admin):
        # フィルターサイドバー用の(値, ラベル)タプルを返す
        return [
            ("this_week", _("今週")),
            ("this_month", _("今月")),
            ("this_year", _("今年")),
            ("unpublished", _("未公開")),
        ]

    def queryset(self, request, queryset):
        # self.value()に基づいてクエリセットをフィルタリング
        today = date.today()
        if self.value() == "this_week":
            return queryset.filter(publish_date__gte=today - timedelta(days=7))
        if self.value() == "this_month":
            return queryset.filter(
                publish_date__year=today.year, publish_date__month=today.month
            )
        if self.value() == "this_year":
            return queryset.filter(publish_date__year=today.year)
        if self.value() == "unpublished":
            return queryset.filter(publish_date__isnull=True)
        return queryset


class ArticleAdmin(admin.ModelAdmin):
    list_filter = [
        "status",
        PublishDateFilter,
        ("author", admin.RelatedOnlyFieldListFilter),  # 記事を持つ著者のみ表示
    ]

# admin.py
from django.contrib import admin
from django.contrib.admin import ShowFacets
from .models import Article


class ArticleAdmin(admin.ModelAdmin):
    list_display = ["title", "status", "category"]
    list_filter = ["status", "category", "author"]
    show_facets = ShowFacets.ALWAYS  # 常にカウントを表示

    # 代替値:
    # ShowFacets.ALLOW - URLに?_facets=1がある場合にカウントを表示
    # ShowFacets.NEVER - カウントを表示しない（大規模データセット用）

# admin.py
from django.contrib import admin
from django.contrib import messages
from django.utils.translation import ngettext
from .models import Article


@admin.action(description="選択した記事を公開", permissions=["change"])
def publish_articles(modeladmin, request, queryset):
    # すでに公開済みの記事を除外
    unpublished = queryset.exclude(status="published")
    updated = unpublished.update(status="published")

    modeladmin.message_user(
        request,
        ngettext(
            "%d件の記事を公開しました。",
            "%d件の記事を公開しました。",
            updated,
        )
        % updated,
        messages.SUCCESS,
    )


@admin.action(description="選択した記事をJSONでエクスポート")
def export_as_json(modeladmin, request, queryset):
    from django.http import HttpResponse
    from django.core import serializers

    response = HttpResponse(content_type="application/json")
    response["Content-Disposition"] = 'attachment; filename="articles.json"'
    serializers.serialize("json", queryset, stream=response)
    return response  # HttpResponseを返すとファイルダウンロードが開始


class ArticleAdmin(admin.ModelAdmin):
    actions = [publish_articles, export_as_json]

    def get_actions(self, request):
        # ユーザー権限に基づいてアクションを条件付きで削除
        actions = super().get_actions(request)
        if not request.user.has_perm("articles.delete_article"):
            del actions["delete_selected"]
        return actions

# admin.py
from django.contrib import admin
from .models import Article, ArticleImage, ArticleComment


class ArticleImageInline(admin.TabularInline):
    model = ArticleImage
    extra = 1  # 表示する空のフォーム数
    max_num = 5  # 記事ごとの最大画像数
    fields = ["image", "caption", "order"]


class ArticleCommentInline(admin.StackedInline):
    model = ArticleComment
    extra = 0
    readonly_fields = ["created_at", "author"]
    can_delete = True


class ArticleAdmin(admin.ModelAdmin):
    fieldsets = [
        (
            None,
            {
                "fields": ["title", "slug", "author"],
            },
        ),
        (
            "コンテンツ",
            {
                "fields": ["content", "excerpt"],
                "classes": ["wide"],  # 全幅フィールド
            },
        ),
        (
            "公開設定",
            {
                "fields": ["status", "publish_date", "category", "tags"],
                "classes": ["collapse"],  # デフォルトで折りたたみ
            },
        ),
        (
            "SEO",
            {
                "fields": ["meta_title", "meta_description"],
                "classes": ["collapse"],
                "description": "検索エンジン最適化フィールド",
            },
        ),
    ]
    inlines = [ArticleImageInline, ArticleCommentInline]
    prepopulated_fields = {"slug": ["title"]}  # タイトルからスラッグを自動生成
    autocomplete_fields = ["author", "category"]  # AJAXパワードセレクト
    filter_horizontal = ["tags"]  # M2M選択用ウィジェット


admin.site.register(Article, ArticleAdmin)

# admin.py
from django.contrib import admin
from django.contrib.admin import AdminSite
from .models import Article, Category


class ContentAdminSite(AdminSite):
    site_header = "コンテンツ管理"
    site_title = "CMS"
    index_title = "ダッシュボード"

    def has_permission(self, request):
        # 'editors'グループのスタッフに制限
        return (
            request.user.is_active
            and request.user.is_staff
            and request.user.groups.filter(name="editors").exists()
        )


content_admin = ContentAdminSite(name="content_admin")
content_admin.register(Article, ArticleAdmin)
content_admin.register(Category)

# urls.py内:
# path('content-admin/', content_admin.urls),

# admin.py
from django.contrib import admin
from .models import Order


class OrderAdmin(admin.ModelAdmin):
    # 間違い: list_select_relatedなしで関連フィールドにアクセス
    # これはN+1クエリを引き起こし、リストビューの各行に1つずつ発生
    list_display = ["id", "customer_email", "total"]

    # 修正: 関連オブジェクトをプリフェッチ
    list_select_related = ["customer"]

    def customer_email(self, obj):
        return obj.customer.email

    # 間違い: インデックスのない大きなテキストカラムでのsearch_fields
    # search_fields = ["notes"]  # 大きなテーブルでは遅い

    # 修正: インデックス付きフィールドに検索を制限
    search_fields = ["id", "customer__email"]

    # 間違い: list_displayでの高コストな計算
    # def order_total(self, obj):
    #     return sum(item.price * item.qty for item in obj.items.all())  # N+1

    # 修正: get_querysetでアノテーションを使用
    def get_queryset(self, request):
        from django.db.models import Sum, F

        qs = super().get_queryset(request)
        return qs.annotate(computed_total=Sum(F("items__price") * F("items__qty")))

    @admin.display(description="合計", ordering="computed_total")
    def total(self, obj):
        return obj.computed_total

# settings.py
INSTALLED_APPS = [
    "unfold",  # django.contrib.adminの前に配置する必要がある
    "unfold.contrib.filters",  # 高度なフィルターウィジェット
    "unfold.contrib.forms",  # 拡張フォームウィジェット
    "django.contrib.admin",
    # ...
]