Problem with 'Cannot assign' error in django

Question

I have something like this in my template.

<form action="" method="POST">
    {% csrf_token %}
     <select name='section'>
      {% for item in all_sections %}
              <option>{{ item.SectionName }}</option>
      {% endfor %}
     </select>
</form>

and in my view.py page:

obj=models.Section.objects.all()
context={
    'all_sections':obj,
}
return render(request,'matab/add-service.html',context)

but i get this is error while saving data:

Cannot assign "'{item}'": "Services.Section" must be a "Section" instance.

also my models.py is like this:

class Section(models.Model):
SectionName=models.CharField(max_length=50)
SectionId=models.CharField(max_length=10)

class Services(models.Model):
Section=models.OneToOneField(
    Section,
    on_delete=models.CASCADE,
)

how can i solve it?

That's just making a lot more work for yourself... options should have a value <option value="{{ item.id }}"> — Iain Shelvington
– Iain Shelvington, Commented Aug 6, 2019 at 10:53
But seriously, just use a ModelForm and it will handle most of the input rendering and input cleaning/conversion — Iain Shelvington
– Iain Shelvington, Commented Aug 6, 2019 at 10:55

dirkgroten · Accepted Answer · 2019-08-06 11:01:51Z

2

Services.Section is a OneToOneField, so you need to assign Section instance, not its name.

Depending on your code, it might work if you set the option value to the pk.

 <select name='section'>
  {% for item in all_sections %}
          <option value="{{ item.pk }}">{{ item.SectionName }}</option>
  {% endfor %}
 </select>

As Iain suggests in the comments, it would be better to change your views to use Django forms instead of manually render select inputs.

edited Aug 6, 2019 at 11:01

dirkgroten

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answered Aug 6, 2019 at 10:52

Alasdair

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