Value Error for Foregin key field - django

Question

I am trying to insert data but am getting ValueError while inserting due to ForeignKey.
class Test(models.Model):
test_name = models.CharField(max_length=20, unique=True)
test_code = models.SlugField(max_length=10, name='Code',unique=True)
referance_value = models.CharField(name='Referance', max_length=20)
def __str__(self):
return self.test_name
class TestTaken(models.Model):
app_code = models.CharField(max_length=20,unique=True)
user_name = models.CharField(name='Username',max_length=20)
test_names = models.ForeignKey(Test, on_delete=models.CASCADE)
result_value = models.CharField(name='ResultValue',max_length=20)
def __str__(self):
return self.app_code
Below is my View.py
def alltestdata(request):
if request.method == 'POST':
app_code = request.POST.getlist('app_code')
test_name = request.POST.getlist('name')
test_list = request.POST.getlist('test_list')
for i, j , k in zip(app_code, test_name, test_list):
book = TestTaken(app_code=i, ResultValue=j, test_names=k, Username=request.user.username)
book.save()
return redirect('lab:Dashboard')
Am geting following error
ValueError: Cannot assign "'eeeee'": "TestTaken.test_names" must be a "Test" instance.

Answer 1

The error holds the answer to your question: test_names is a ForeignKey, not a string. To set it from a name, you first need to find the key into the Test table. This can be done with a get or get_or_create, depending on how you want to handle missing tests.
NOTE: test_names is not a very good name for that ForeignKey field and probably caused this confusion. It shouldn't be plural, and points to a Test object, not just a name. You probably want something more like test
There is some additional confusion in your code. First, you seem to have swapped values in your inner iteration (j gets its value from test_name and is then applied to ResultValue, while k comes from test_list but goes to test_names instead). You can avoid confusion like this by using more explicit variable names. The second source of confusion is in the variable names app_code, test_name, and test_list, all of which seem to be lists, but only one of them has a name that seems to reflect this.
Combining these points into code, try something like the following. Note that I have changed some of the names of variables to reflect what I think you intended, and I have used a simple get_or_create, while you might want something else. Adjust to suit your needs:
# in your model
class Test(models.Model):
test_name = models.CharField(max_length=20, unique=True)
test_code = models.SlugField(max_length=10, name='Code',unique=True)
referance_value = models.CharField(name='Referance', max_length=20)
def __str__(self):
return self.test_name
class TestTaken(models.Model):
app_code = models.CharField(max_length=20,unique=True)
user_name = models.CharField(name='Username',max_length=20)
test = models.ForeignKey(Test, on_delete=models.CASCADE)
result_value = models.CharField(name='ResultValue',max_length=20)
def __str__(self):
return self.app_code
# in View.py
def alltestdata(request):
if request.method == 'POST':
app_codes = request.POST.getlist('app_code')
test_names = request.POST.getlist('name')
scores = request.POST.getlist('test_list')
for code, test_name, score in zip(app_codes, test_names, scores):
test_obj, _ = Test.objects.get_or_create(test_name=test_name)
book = TestTaken(app_code=code, ResultValue=score, test=test_obj, Username=request.user.username)
book.save()
return redirect('lab:Dashboard')