Django查询：从不直接相关的模型中获取值

Question

我想从Django中不直接相关的模型中获取值。 我有以下型号：

class Platform(models.Model): 
    platform = models.CharField() 


class Game(models.Model): 
    game = models.CharField() 
    genre = models.CharField() 


class Link(models.Model): 
    game = models.ForeignKey(Game) 
    platform = models.ForeignKey(Platform) 

我怎么能得到游戏的QuerySet对象，其中游戏标题（Game.game场）将被替换到以下模式：游戏（平台）（例如“战地（PS3）”。 ）没有额外的命中数据库？

在SQL它应该是这样的：

SELECT 
    g.id, 
    g.game || ' (' || p.platform || ')' AS game 
FROM game g INNER JOIN link l ON g.id = l.game_id 
    LEFT JOIN platform p ON l.platform_id = p.id; 

Answer 1

您可以使用link_set获得游戏反向查找，这里的django documentation

class Platform(models.Model): 
    platform = models.CharField() 


class Game(models.Model): 
    game = models.CharField() 
    genre = models.CharField() 

    def save(self, *args, **kwargs): 
     self.title = "{0} ({1})".format(self.title, self.link__platform) 
     super(Game, self).save(*args, **kwargs) 


class Link(models.Model): 
    class Meta: 
     unique_together = ('game', 'platform') 
    game = models.ForeignKey(Game) 
    platform = models.ForeignKey(Platform)