CODEWITHSUNDEEP
pythondjangomigration
CoderBrain
CoderBrain

Reputation: 103

'ForeignKey' object has no attribute

When I try to make migrations for the following models: 

class Location(models.Model):
    name = models.CharField(max_length=200)
    latitude = models.FloatField
    longitude = models.FloatField
    altitude = models.IntegerField

    def _str_(self):
        return self.name

    def getLatitude(self):
        return self.latitude

    def getLongitude(self):
        return self.longitude

class Distance(models.Model):
    placeA = models.ForeignKey(Location, on_delete=models.CASCADE)
    placeB = models.ForeignKey(Location, on_delete=models.CASCADE)
    placeAlatitude = placeA.getLatitude()
    placeBlatitude = placeB.getLatitude()
    placeAlongitude = Location.objects.select_related().get(placeA.longitude)
    placeBlongitude = Location.objects.select_related().get(placeB.longitude)
    distance = models.FloatField(default = 0.0)

I am getting the error:

'ForeignKey' object has no attribute 'getLatitude'

I get a similar error if I try to directly access the latitude directly (placeA.latitude)

What am I doing wrong? I am new to using the Django framework.

Upvotes: 2

Views: 10206

Answers (2)

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 477814

First of all there is likely an error in your Location model: you here do not construct the FloatFields and IntegerField: you only pass a reference to the class, you do not "call" it. So in order to define these columns, you should add parenthesis:

class Location(models.Model):
    name = models.CharField(max_length=200)
    latitude = models.FloatField()
    longitude = models.FloatField()
    altitude = models.IntegerField()

    # ...

Next you can not define placeAlatitude, etc. with placeA.GetLatitude(), at class level placeA is a ForeignKey object, not a Location, object, you can however define a @property here that will, for a Distance object, fetch the correct attribute of the related objects:

class Distance(models.Model):
    placeA = models.ForeignKey(Location, on_delete=models.CASCADE)
    placeB = models.ForeignKey(Location, on_delete=models.CASCADE)
    distance = models.FloatField(default = 0.0)

    @property
    def placeAlatitude(self):
        return self.placeA.latitude

    @property
    def placeBlatitude(self):
        return self.placeB.latitude

    @property
    def placeAlongitude(self):
        return self.placeA.longitude

    @property
    def placeBlongitude(self):
        return self.placeB.longitude

Upvotes: 7

a_k_v
a_k_v

Reputation: 1608

In your model, you are defining the structure. You can't use 

placeAlatitude = placeA.getLatitude()
placeBlatitude = placeB.getLatitude()

placeAlatitude and placeBlatitude must be define the type of model. You can't simply return value.

From analyzing your model these two fields are not necessary it is redundant values(same case for placeAlongitude and placeBlongitude). You defined a foreign key relation to location. So you can access longitude and latitude by using that relation.

Upvotes: 1

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