Custom field implementing Boolean Field is having response value as None instead of False
Priyanka Thakur
from django.db import models
class HibernateBooleanField(models.BooleanField):
def from_db_value(self, value, expression, connection, context):
return self.to_python(value)
def get_internal_type(self):
return "HibernateBooleanField"
def db_type(self, connection):
return 'bit(1)'
def to_python(self, value):
if value in (True, False):
return value
if value in ('t', 'True', 'true', '1', '\x01'): return True
if value in ('f', 'False', 'false', '0', '\x00', None): return False
def get_db_prep_value(self, value, connection, prepared=False):
return 0x01 if value else 0x00
def get_db_prep_save(self, value, connection):
return 0x01 if value else 0x00
def get_prep_value(self, value):
return self.to_python(value)
---
I have defined a field in the model as:
class MetaMetadata(models.Model):
is_folder = HibernateBooleanField()
When I invoke a POST request on API in my test case , I get the value for this field as "None" in response.
The API is :
response = self._client.post('/xyz/api/metametadatas/',
{'edit_view': "TestEditView",
'grid_view': "TestGridView",
'name': "Test Metametadata",
'sort_key': 9000,
'parentid': 0,
'version':0,
'id': 100}, format='json')
Please explain , what is it that I'm doing wrong. Why isn't to_python method getting invoked ? Am I missing something?
Regards,
Priyanka
Melvyn Sopacua
On Friday 16 June 2017 07:33:22 Priyanka Thakur wrote:
> Hi,
>
> I am doing migration from Django 1.7 to 1.10 version and has a custom
> django field.
>
> Below is the custom class for the field:
>
> ----
>
> from django.db import models
>
>
>
> class HibernateBooleanField(models.BooleanField):
>
> def from_db_value(self, value, expression, connection, context):
>
> return self.to_python(value)
>
>
> def get_internal_type(self):
>
> return "HibernateBooleanField"
>
>
> def db_type(self, connection):
>
> return 'bit(1)'
>
>
> def to_python(self, value):
>
> if value in (True, False):
>
> return value
>
> if value in ('t', 'True', 'true', '1', '\x01'): return True
>
> if value in ('f', 'False', 'false', '0', '\x00', None): return
> False
and if value is something else, nothing (aka None) is returned. You have no else clause here.
--
Melvyn Sopacua
Priyanka Thakur
> if value in ('f', 'False', 'false', '0', '\x00', None): return
> False
--copy--
Thanks for checking and replying !!
Regards,
Priyanka
m712 - Developer
Melvyn was not saying whether you were checking for None. If `value` is i.e. "some string" your to_python method will return `None`. You should do something like this:
```
if value in ('t', ...): return True
elif value in ('f', ...): return False
else: return bool(value) # You can change this
```
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Priyanka Thakur
Melvyn Sopacua
On Monday 19 June 2017 04:00:42 Priyanka Thakur wrote:
> On Monday, 19 June 2017 16:05:06 UTC+5:30, m712 - Developer wrote:
> > Melvyn was not saying whether you were checking for None. If `value`
> > is i.e. "some string" your to_python method will return `None`. You
> > should do something like this:
> >
> > ```
> >
> > if value in ('t', ...): return True
> > elif value in ('f', ...): return False
> > else: return bool(value) # You can change this
> >
> > ```
That's correct for to_python. But personally, I would raise an exception in from_db_value, since that indicates data corruption.
In your case, there are only a handful of allowed values that should come from the database. Anything else, will indicate somebody messing with your data or upgrades of one of the libraries in between Django and the database changed it's output format. Both of which will require attention.
This is one advantage of from_db_value and to_python separation.
--
Melvyn Sopacua