Django查詢：從不直接相關的模型中獲取值

Question

我想從Django中不直接相關的模型中獲取值。 我有以下型號：

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) 

我怎麼能得到遊戲的QuerySet對象，其中游戲標題（Game.game場）將被替換到以下模式：遊戲（平臺）（例如「戰地（PS3）」。 ）沒有額外的命中數據庫？

在SQL它應該是這樣的：

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獲得遊戲反向查找，這裏的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)