Question

我正在使用django import-export库来处理数据。它运行良好，除了我无法导入外键中尚不存在的对象。

如果外键模型中存在对象（csv中的值），则导入正常。

但是如果外键模型中不存在对象/值，则表示“匹配查询不存在”，并且不会导入数据。

如果外键中不存在新对象，我怎么能告诉它将新对象添加到外键模型？

Models.py代码段

class Store(models.Model):

    store_name = models.CharField(max_length=30)
    def __unicode__(self):
        return self.store_name
    #etc

class Product(models.Model):

    Store = models.ForeignKey(Store)
    Category = models.ForeignKey(Category)
    first_name = models.CharField(max_length=30)
    second_name = models.CharField(max_length=30)
...

Admin.py代码段

admin.site.register(Category)
admin.site.register(Store)

class ProductResource(resources.ModelResource):

     store_name = fields.Field(column_name='store_name', attribute='Store',
                       widget=ForeignKeyWidget(Store, 'store_name'))

    def __unicode__(self):
        return self.store_name.name

    class Meta:
        model = Product
        fields = ('id', 'first_name', 'second_name','store_name')
        export_order = ('id', 'second_name', 'first_name')
        skip_unchanged = False
        report_skipped = False
        widgets = {
                'published': {'format': '%d.%m.%Y'},
                }


class ProductAdmin(ImportExportModelAdmin):
    resource_class = ProductResource
    list_display = ('first_name', 'second_name')

admin.site.register(Product, ProductAdmin)

Answer 1

在ForeignKeyWidget你有方法

  def clean(self, value):
        val = super(ForeignKeyWidget, self).clean(value)
        return self.model.objects.get(**{self.field: val}) if val else None

您可以尝试覆盖它以执行get_or_create ...

之类的操作它应该看起来像这样...

from import_export.widgets import ForeignKeyWidget
class MyCustomizationToFKWidget(ForeignKeyWidget):

      def clean(self, value):
            val = super(ForeignKeyWidget, self).clean(value)
            HERE SOME LOGIC OVERRIDEN

Answer 2

如果您的模型的ForeignKey可以为null：

MyForeignKeyName = Models.ForeignKey(<modelclass>,blank=True, null=True)

您可以在Resource类中添加before_import_row()方法：

def before_import_row(self,row) :
    fieldname = 'MyForeignKeyName'
    if not( <modelclass>.objects.filter(pk=row[fieldname]).exists() ) :
        # print(row['id'],row[fieldname],'unknown key !') # console log
        row[fieldname ] = None # or something else.. *

* ..符合您的foreignkey configuration [python None = SQL null]

我对Django有点新意，所以也许这不是更好的方法，但这解决了我的问题。

还有一些关于db_constraint = False的东西，可以添加到ForeignKey的参数（一些信息@stackoverflow和@django）但是，我找不到我的方式它

Answer 3

您可以在Resource类的before_import_row()方法中创建缺少的外键条目：

class ProductResource(resources.ModelResource):
    ...
    def before_import_row(self, row, **kwargs):
        Store.objects.get_or_create(
            store_name=row.get('store_name')
        )

Answer 4

我发现最好的方法是使用自定义小部件。我在 django-import-export GitHub 项目 here 上找到了一个线程，其中包含很多有用的信息。从中我拼凑了这两个支持创建新对象的自定义小部件。通过将它们添加到您的 failed_jobs 模块中，这些应该都能正常工作：

admin.py

您可以像这样在导入-导出模型资源类中使用这些：

from import_export.widgets import ManyToManyWidget
from django.db.models import QuerySet


class ForeignKeyWidgetWithCreation(ForeignKeyWidget):
    """
    Taken from a GitHub post.
    https://github.com/django-import-export/django-import-export/issues/318#issuecomment-139989178
    """

    def __init__(self, model, field="pk", create=False, **kwargs):
        self.model = model
        self.field = field
        self.create = create
        super(ForeignKeyWidgetWithCreation, self).__init__(model, field=field, **kwargs)

    def clean(self, value, **kwargs):
        if not value:
            return None

        if self.create:
            self.model.objects.get_or_create(**{self.field: value})

        val = super(ForeignKeyWidgetWithCreation, self).clean(value, **kwargs)

        return self.model.objects.get(**{self.field: val}) if val else None


class ManyToManyWidgetWithCreation(ManyToManyWidget):
    """
    Taken from a GitHub post.
    https://github.com/django-import-export/django-import-export/issues/318#issuecomment-139989178
    """

    def __init__(self, model, field="pk", create=False, **kwargs):
        self.model = model
        self.field = field
        self.create = create
        super(ManyToManyWidgetWithCreation, self).__init__(model, field=field, **kwargs)

    def clean(self, value, **kwargs):

        # If no value was passed then we don't have anything to clean.

        if not value:
            return self.model.objects.none()

        # Call the super method. This will return a QuerySet containing any pre-existing objects.
        # Any missing objects will be

        cleaned_value: QuerySet = super(ManyToManyWidgetWithCreation, self).clean(
            value, **kwargs
        )

        # Value will be a string that is separated by `self.separator`.
        # Each entry in the list will be a reference to an object. If the object exists it will
        # appear in the cleaned_value results. If the number of objects in the cleaned_value
        # results matches the number of objects in the delimited list then all objects already
        # exist and we can just return those results.

        object_list = value.split(self.separator)

        if len(cleaned_value.all()) == len(object_list):
            return cleaned_value

        # If we are creating new objects then loop over each object in the list and
        # use get_or_create to, um, get or create the object.

        if self.create:
            for object_value in object_list:
                _instance, _new = self.model.objects.get_or_create(
                    **{self.field: object_value}
                )

        # Use `filter` to re-locate all the objects in the list.

        model_objects = self.model.objects.filter(**{f"{self.field}__in": object_list})

        return model_objects

Django在foriegn密钥模型中导入导出新值

4 个答案: