Question

In models.py I have…

class Siteinfo(models.Model):
    url = models.CharField(max_length=100)
    description = models.TextField()    

class Makesite(models.Model):
    sitename = models.CharField(max_length=100, unique = True) 
    siteinfo = models.ManyToManyField(Siteinfo)
    ref_id = models.ManyToManyField(RefID)
    def __unicode__(self):
        return u'%s' %(self.sitename)

I’m trying to delete a instance of description and replace it with another instance and still have it be associated with the same url and still be the many to many object under say. Group on.

So group1 is the site name. to create the relation I have

url = request.POST['url']
description = request.POST['description']

datsite = Makesite.objects.get(sitename=site)
datsite.siteinfo.add(Siteinfo.objects.create(url=url,description=description))

But then when I try to delete and replace the description with this bit of code it also deletes the url.

name = Makesite.objects.get(sitename=site).siteinfo.values_list('description',flat=True)[0]
Makesite.objects.get(sitename=site).siteinfo.get(description=name).delete()

I guess I could try to write some code that could get around this problem but I’d rather find a way to just delete one and add another instance in its place.

Answer 1

Just to be picky, you should be using forms for processing user input.

It sounds like you want to be updating an instance, not deleting and adding one nearly exactly the same.

site_info = Makesite.objects.get(sitename=site).siteinfo.get(description=name)
site_info.description = "new description"
site_info.save()

Or, more simply:

site_info = Siteinfo.objects.get(makesite__sitename=site, description=name) # only 1 query
site_info.description = "new description"
site_info.save()