On Wednesday, December 5, 2012 8:35:38 PM UTC+1, len wrote:
>
> I am new to web2py and have been going through the books and examples and
> was wondering if when creating foreign-key if 'reference tablename' or
> db.tablename is better to use.
> I looked in the 4th edition of the book and there is an example where a
> table has multiple references to itself;
>
> db.define_table('person',
> Field('mother', 'reference person' ...
> Field('father', 'reference person' ...
>
> and it indicates 'reference person' should be used in that case. Which
> should be used.
>
> small disclaimer: db.person exists only AFTER db.define_table('person',
.....) so you can't use *db.person* in db.define_table('person', ....).
'reference tablename' is the *recommended* way for ALL foreign keys
> Should length normally be supplied for field types that accept it?
>
length defaults to 512. If you don't set it explicitely, 512 will be used
in most databases.
> When defining the type of field should you use type='string' or 'string'
> or does it matter?
>
This is more a python question than a web2py one. there are named arguments
and positional arguments. Current signature of the Field class is
fieldname,
type='string',
length=None,
default=DEFAULT,
required=False,
requires=DEFAULT,
ondelete='CASCADE',
notnull=False,
unique=False,
uploadfield=True,
widget=None,
label=None,
comment=None,
writable=True,
readable=True,
update=None,
authorize=None,
autodelete=False,
represent=None,
uploadfolder=None,
uploadseparate=False,
uploadfs=None,
compute=None,
custom_store=None,
custom_retrieve=None,
custom_retrieve_file_properties=None,
custom_delete=None,
filter_in = None,
filter_out = None,
custom_qualifier = None,
So, if you do Field('something', 'string', 30) it will be the same as
Field('something', type='string', length=30). It's just a matter of being
explicit vs implicit.
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