Django模型中的ManyToMany关系

Question

I'm trying to add relation between three table with manyToMany relationship. I'm learning python and new for Django framework. For requirement, An user can add a project and he also can add permission for view for another user. It means an user can have multiple projects and a project also have multiple user. User model is default user model of django.

and the project model is:

Projects/model.py

from django.db import models
from django.contrib.auth.models import User
# Create your models here.


class Projects(models.Model):
    project_title = models.CharField(max_length=255)
    description = models.TextField(blank=True)
    privacy = models.SmallIntegerField(default=1) # 1 for public, 2 for private
    status = models.SmallIntegerField(default=1) #1 for active, 2 for deactive, 3 for delete, 4 for depricated
    created_at = models.DateTimeField('date published', blank=True, default=False)
    users = models.ManyToManyField(User, through="UserProjects")

class UserProjects(models.Model):
    user = models.ForeignKey(User,blank=True, default=False)
    project = models.ForeignKey(Projects,blank=True)
    owner = models.SmallIntegerField(default=1)

It's not working. When i'm add a project is produce some error..

Traceback (most recent call last):
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\core\handlers\exception.py", line 41, in inner
    response = get_response(request)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\core\handlers\base.py", line 187, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\core\handlers\base.py", line 185, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "E:\Programs\Python\RestClient\Projects\views.py", line 29, in add
    p.save()
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\base.py", line 806, in save
    force_update=force_update, update_fields=update_fields)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\base.py", line 836, in save_base
    updated = self._save_table(raw, cls, force_insert, force_update, using, upda
te_fields)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\base.py", line 922, in _save_table
    result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\base.py", line 961, in _do_insert
    using=using, raw=raw)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\query.py", line 1063, in _insert
    return query.get_compiler(using=using).execute_sql(return_id)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\sql\compiler.py", line 1098, in execute_sql
    for sql, params in self.as_sql():
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\sql\compiler.py", line 1051, in as_sql
    for obj in self.query.objs
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\sql\compiler.py", line 1051, in <listcomp>
    for obj in self.query.objs
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\sql\compiler.py", line 1050, in <listcomp>
    [self.prepare_value(field, self.pre_save_val(field, obj)) for field in field
s]
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\sql\compiler.py", line 990, in prepare_value
    value = field.get_db_prep_save(value, connection=self.connection)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\fields\__init__.py", line 770, in get_db_prep_save
    prepared=False)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\fields\__init__.py", line 1459, in get_db_prep_value
    value = self.get_prep_value(value)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\fields\__init__.py", line 1438, in get_prep_value
    value = super(DateTimeField, self).get_prep_value(value)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\fields\__init__.py", line 1296, in get_prep_value
    return self.to_python(value)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\db\models\fields\__init__.py", line 1399, in to_python
    parsed = parse_datetime(value)
  File "C:\Users\Jitendra\AppData\Local\Programs\Python\Python35-32\lib\site-pac
kages\django\utils\dateparse.py", line 94, in parse_datetime
    match = datetime_re.match(value)
TypeError: expected string or bytes-like object
[28/Jul/2017 22:25:10] "POST /projects/add/ HTTP/1.1" 500 145532

And here the projects/view.py

def add(request):
    form = ProjectForm()
    if request.method == "POST":
        form = ProjectForm(request.POST)
        if form.is_valid():
            p = Projects(project_title=request.POST.get("project_title"), description=request.POST.get("description"),
                         status=1, privacy=1)
            p.save()
            sp = UserProjects(user_id=request.user.id, project_id=p.id)
            sp.save()
            p.users.add(sp)
            messages.success(request, 'Profile details updated.')

    view_data = {
        "form": form,
        'title': "Add new project"
    }
    return render(request, 'projects/add.html', view_data)

I dont know, whats wrong with it. Please guide me. Thanks

Answer 1

From Django docs :

class DateTimeField(**kwargs)

Default widget: DateTimeInput

Empty value: None

Normalizes to: A Python datetime.datetime object.

Validates that the given value is either a datetime.datetime, datetime.date or string formatted in a particular datetime format.

Error message keys: required, invalid

You can read that DateTimeField validates that given value is either datetime.datetime, datetime.date or string formatted in particular datetime format, however you set default=False in your model definitions. So I would guess the problem lays in there.