Django高級編程之自定義Field實現多語言

自定義資料庫欄位

擴展預設的models.CharField和models.TextField使之成為支持多語言的欄位。
可以輕鬆實現復用，無需配置多餘選項

from django.conf import settings
from django.db import models
from django.utils.translation import get_language


class MultilingualField(models.Field):
    SUPPORTED_FIELD_TYPES = [models.CharField, models.TextField]

    def __init__(self, verbose_name=None, **kwargs):
        self.localized_field_model = None
        for model in MultilingualField.SUPPORTED_FIELD_TYPES:
            if issubclass(self.__class__, model):
                self.localized_field_model = model
        self._blank = kwargs.get("blank", False)
        self._editable = kwargs.get("editable", True)
        super().__init__(verbose_name, **kwargs)

    @staticmethod
    def localized_field_name(name, lang_code):
        lang_code_safe = lang_code.replace("-", "_")
        return f"{name}_{lang_code_safe}"

    def get_localized_field(self, lang_code, lang_name):
        _blank = (self._blank
                  if lang_code == settings.LANGUAGE_CODE
                  else True)
        localized_field = self.localized_field_model(
            f"{self.verbose_name} ({lang_name})",
            name=self.name,
            primary_key=self.primary_key,
            max_length=self.max_length,
            unique=self.unique,
            blank=_blank,
            null=False, # we ignore the null argument!
            db_index=self.db_index,
            default=self.default or "",
            editable=self._editable,
            serialize=self.serialize,
            choices=self.choices,
            help_text=self.help_text,
            db_column=None,
            db_tablespace=self.db_tablespace)
        return localized_field

    def contribute_to_class(self, cls, name,
                            private_only=False):
        def translated_value(self):
            language = get_language()
            val = self.__dict__.get(
                MultilingualField.localized_field_name(
                        name, language))
            if not val:
                val = self.__dict__.get(
                    MultilingualField.localized_field_name(
                            name, settings.LANGUAGE_CODE))
            return val

        # generate language-specific fields dynamically
        if not cls._meta.abstract:
            if self.localized_field_model:
                for lang_code, lang_name in settings.LANGUAGES:
                    localized_field = self.get_localized_field(
                        lang_code, lang_name)
                    localized_field.contribute_to_class(
                            cls,
                            MultilingualField.localized_field_name(
                                    name, lang_code))

                setattr(cls, name, property(translated_value))
            else:
                super().contribute_to_class(
                    cls, name, private_only)


class MultilingualCharField(models.CharField, MultilingualField):
    pass


class MultilingualTextField(models.TextField, MultilingualField):
    pass

這裡定義了 MultilingualCharField 和 MultilingualTextField欄位

使用方法

settings.py中配置多語言

LANGUAGE_CODE = 'zh-hans'
TIME_ZONE = 'Asia/Shanghai'

LANGUAGES = (
    ('en-us', 'US English'),
    ('zh-hans', 'Asia/Shanghai')
)

預設語言設置為中文，多語言為英語

models.py中使用欄位

from django.db import models
from django.utils.translation import ugettext_lazy as _

from utils.fields import (
    MultilingualCharField,
    MultilingualTextField
)

class Item(models.Model):
    title = MultilingualCharField(_('Title'), max_length=200)
    description = MultilingualTextField(_('Description'), blank=True)
    content = MultilingualTextField(_('Content'))

    def __str__(self):
        return self.title

效果圖

可以看到，資料庫欄位自動生成了相應語言的欄位

當用戶語言切換到其他，可以自動適配實現多語言