django-modeltranslation启用时，动态添加ModelForm字段后翻译值无法保存的问题排查与解决问询

嘿，这个坑我之前也踩过！核心原因其实很直白：Django的ModelForm只会自动处理Meta.fields里声明的字段，或者由modeltranslation自动关联生成的字段。你手动动态添加的description_es这类字段，不在ModelForm的“自动处理清单”里，所以哪怕cleaned_data里已经有正确的值，form.save()的时候也不会把这些值同步到模型实例上。

给你两个实用的解决办法，选哪个看你的代码习惯：

方法一：重写表单save方法，手动赋值动态字段 #

这个方法最直接，我们自己接管动态字段的值赋值工作。首先在你的DefaultModelForm里新增save方法，同时在__init__里记录下所有动态添加的字段名：

class DefaultModelForm(forms.ModelForm):

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        # 新增实例变量，记录所有动态添加的翻译字段名
        self.added_translation_fields = []
        if user := self.request and self.request.user:
            company = user.company
            app_setting = company.settings
            default_lang = settings.MODELTRANSLATION_DEFAULT_LANGUAGE  # "en"
            default_search = f"_{default_lang}"
            to_add = []

            """Set field_order to the same order as set in Meta.fields, unless already set"""
            if self.field_order is None:
                self.field_order = list(self.Meta.fields)

            for modelfield in self._meta.model._meta.fields:
                """If we found a default translation field, add it to the list"""
                if (
                    (formfield := self.fields.get(modelfield.name, None))
                    and modelfield.name.endswith(default_search)
                    and isinstance(modelfield, TranslationField)
                ):
                    to_add.append(
                        {
                            "position": self.field_order.index(modelfield.name),
                            "formfield": deepcopy(formfield),
                            "name": modelfield.name.removesuffix(default_search),  # "description"
                            "languages": app_setting.get_additional_language_codes,  # ["es"]
                        }
                    )

            for addable in to_add:
                for lang in addable.get("languages"):
                    field_name = f"{addable.get('name')}_{lang}"  # "description_es"
                    formfield = addable.get("formfield")
                    formfield.label = formfield.label.replace(f"[{default_lang}]", f"[{lang}]")
                    formfield.required = False
                    formfield.initial = getattr(self.instance, field_name, "")
                    self.fields[field_name] = formfield
                    # 记录添加的字段名
                    self.added_translation_fields.append(field_name)
                    self.field_order.insert(addable.get("position", 0) + 1, field_name)

            self.order_fields(self.field_order)

    def save(self, commit=True):
        # 先调用父类save方法，暂不提交到数据库
        instance = super().save(commit=False)
        # 遍历动态字段，把cleaned_data的值赋值给实例
        for field_name in self.added_translation_fields:
            if field_name in self.cleaned_data:
                setattr(instance, field_name, self.cleaned_data[field_name])
        # 提交保存（如果需要）
        if commit:
            instance.save()
        return instance

方法二：动态更新Meta.fields，让ModelForm自动处理 #

如果你想让ModelForm自己处理这些字段，可以在__init__里把动态添加的字段加入到self._meta.fields中，这样Django会自动同步字段值到实例：

def __init__(self, *args, **kwargs):
    super().__init__(*args, **kwargs)
    # 存储要添加的额外字段
    additional_fields = []
    if user := self.request and self.request.user:
        company = user.company
        app_setting = company.settings
        default_lang = settings.MODELTRANSLATION_DEFAULT_LANGUAGE  # "en"
        default_search = f"_{default_lang}"
        to_add = []

        """Set field_order to the same order as set in Meta.fields, unless already set"""
        if self.field_order is None:
            self.field_order = list(self.Meta.fields)

        for modelfield in self._meta.model._meta.fields:
            """If we found a default translation field, add it to the list"""
            if (
                (formfield := self.fields.get(modelfield.name, None))
                and modelfield.name.endswith(default_search)
                and isinstance(modelfield, TranslationField)
            ):
                to_add.append(
                    {
                        "position": self.field_order.index(modelfield.name),
                        "formfield": deepcopy(formfield),
                        "name": modelfield.name.removesuffix(default_search),  # "description"
                        "languages": app_setting.get_additional_language_codes,  # ["es"]
                    }
                )

        for addable in to_add:
            for lang in addable.get("languages"):
                field_name = f"{addable.get('name')}_{lang}"  # "description_es"
                formfield = addable.get("formfield")
                formfield.label = formfield.label.replace(f"[{default_lang}]", f"[{lang}]")
                formfield.required = False
                formfield.initial = getattr(self.instance, field_name, "")
                self.fields[field_name] = formfield
                additional_fields.append(field_name)
                self.field_order.insert(addable.get("position", 0) + 1, field_name)

        # 更新Meta.fields，加入额外字段（转成列表避免元组不可修改）
        self._meta.fields = list(self._meta.fields) + additional_fields
        self.order_fields(self.field_order)

这两种方法都能解决你的问题，修改后再调试，应该就能看到self.object.description_es拿到正确的POST值啦！

备注：内容来源于stack exchange，提问作者kunambi