Django的through模型
示例
class Skill(models.Model):
name = models.CharField(max_length=50)
description = models.TextField()
class Developer(models.Model):
name = models.CharField(max_length=50)
skills = models.ManyToManyField(Skill, through='DeveloperSkill')
class DeveloperSkill(models.Model):
"""具有相应能力和经验的开发人员技能。"""
class Meta:
order_with_respect_to = 'developer'
"""Sort skills per developer so that he can choose which
skills to display on top for instance.
"""
unique_together = [
('developer', 'skill'),
]
"""It's recommended that a together unique index be created on
`(developer,skill)`. This is especially useful if your database is
being access/modified from outside django. You will find that such an
index is created by django when an explicit through model is not
being used.
"""
ABILITY_CHOICES = [
(1, "Beginner"),
(2, "Accustomed"),
(3, "Intermediate"),
(4, "Strong knowledge"),
(5, "Expert"),
]
developer = models.ForeignKey(Developer, models.CASCADE)
skill = models.ForeignKey(Skill, models.CASCADE)
"""The many-to-many relation between both models is made by the
above two foreign keys.
Other fields (below) store information about the relation itself.
"""
ability = models.PositiveSmallIntegerField(choices=ABILITY_CHOICES)
experience = models.PositiveSmallIntegerField(help_text="多年经验。")建议在上创建一个唯一索引(developer,skill)。如果要从django外部访问/修改数据库，这将特别有用。您会发现，当不使用显式直通模型时，django会创建这样的索引。