Question

我希望将项目添加到django模型中的manytomany字段中。目前正在创建新的标记对象，但是当我在管理员中调用save时，它不会被添加到MyModel。我的代码没有任何错误，有什么想法吗？

class Tag(models.Model):
    text = models.SlugField(max_length=50, unique=True)


class MyModel(models.Model):
    tags = models.ManyToManyField("Tag", blank=True)

    def save(self, *args, **kwargs):
        if (self.tags.count() == 0):
            tag, created = Tag.objects.get_or_create(text=get_word())
            tag.save()
            self.tags.add(tag)

        return super(MyModel, self).save(*args, **kwargs)

Answer 1

首先你需要保存MyModel实例，然后使用self.tags.add（tag）

class MyModel(models.Model):
    tags = models.ManyToManyField("Tag", blank=True)

    def save(self, *args, **kwargs):
        super(MyModel, self).save(*args, **kwargs) # saving MyModel instance

        tag, created = Tag.objects.get_or_create(text=get_word())
        tag.save()
        self.tags.add(tag) # adding m2m to saved instance MyModel

        return self

Answer 2

为了向ManyToMany字段添加一些值，您可以使用post_save信号

from django.db.models.signals import post_save
from django.dispatch import receiver

class MyModel(models.Model):
    tags = models.ManyToManyField("Tag", blank=True)


@receiver(post_save, sender=MyModel)
def update_related_doc_sync(sender, instance, **kwargs):
    # get or create Tag - no need to call .save()
    tag, created = Tag.objects.get_or_create(text=get_word())
    # add tag to M2M field
    instance.tags.add(tag)

在Django中保存时将对象添加到ManyToMany字段

2 个答案: