引用其他模型的字段

Question

在我的第一次旅程進入django世界我想擁有一個模型unicode函數引用另一個模型unicode函數與外鍵引用。這是我已經和它不工作

class Rider(models.Model): 
    first_name = models.CharField(max_length=30) 
    last_name = models.CharField(max_length=30) 
    def __unicode__(self): 
     return self.first_name + " " + self.last_name 

class Ride(models.Model): 
    ride_name = models.CharField(max_length=200) 
    ride_meeting_place = models.CharField(max_length=2000) 
    ride_description = models.CharField(max_length=2000) 
    ride_leader = models.ForeignKey(Rider) 
    ride_date = models.DateTimeField('date of ride') 
    ride_miles = models.FloatField('scheduled miles') 
    def __unicode__(self): 
     return self.ride_name 

class Miles(models.Model): 
    rider_id = models.ForeignKey(Rider) 
    ride_id = models.ForeignKey(Ride) 
    actual_miles = models.FloatField('actual miles') 
    def __unicode__(self): 
     return self.rider_id + " " + self.ride_id + " " + self.actual_miles 

最後一行是我遇到的麻煩之一。

Answer 1

我會收拾你的模型了一下：

class Rider(models.Model): 
    first_name = models.CharField(max_length=30) 
    last_name = models.CharField(max_length=30) 
    def __unicode__(self): 
     return self.first_name + " " + self.last_name 

class Ride(models.Model): 
    name = models.CharField(max_length=200) 
    meeting_place = models.CharField(max_length=2000) 
    description = models.CharField(max_length=2000) 
    leader = models.ForeignKey(Rider) 
    date = models.DateTimeField('date of ride') 
    miles = models.FloatField('scheduled miles') 
    def __unicode__(self): 
     return self.name 

class Miles(models.Model): 
    rider = models.ForeignKey(Rider) 
    ride = models.ForeignKey(Ride) 
    actual_miles = models.FloatField('actual miles') 
    def __unicode__(self): 
     return "%s %s %s" % (self.rider, self.ride, self.actual_miles) 

無需前言所有Ride領域與ride_。

不要叫你的外鍵rider_id，只需使用rider（同樣與ride_id）

然後使用字符串格式化強制統一。

Answer 2

你並不需要添加前綴_id：

class Miles(models.Model): 
    rider = models.ForeignKey(Rider) 
    ride = models.ForeignKey(Ride) 
    actual_miles = models.FloatField('actual miles') 

    def __unicode__(self): 
     return "%s %s %s" % (self.rider, self.ride, self.actual_miles) 

通過使用字符串格式化，你實際上是在加入str(self.rider)，str(self.ride)和str(self.actual_miles)，這意味着調用引擎蓋下self.rider.__unicode__()和self.ride.__unicode()__。從docs報價：

If you define a __unicode__() method on your model and not a __str__() method, Django will automatically provide you with a __str__() that calls __unicode__() and then converts the result correctly to a UTF-8 encoded string object. This is recommended development practice: define only __unicode__() and let Django take care of the conversion to string objects when required.