Iif you want virtual fields to show up in a query over a single table they
have to be defined in that table, otherwise you need to join a table where
they exist.
The definition of a virtual field needs a name and usually a lambda
function over fields in a row.
Lets add a virtual field to the auth_user table:
db.auth_user.full_name = Field.Virtual('full_name', lambda row: '%s %s' %(
row.auth_user.first_name, row.auth_user.last_name))
Now everytime you retrieve rows from auth_user, whether directly or via a
join, they will have a field called full_name.
There are also Method fields which are functions than can be called to
obtain a value.
db.items.createdbyfullname = Field.Method('createdbyfullname',
lambda row: db(db.auth_user.id==row.items.created_by).select()[0].
full_name)
So now, after retrieving rows from item, you can call the row's
createdbyfullname function to get the full name of the user that created
the entry.
Note that is over simplified but helps to illustrate the use.
Denes
On Thursday, January 21, 2016 at 5:24:00 PM UTC-5, Oliva Lemke wrote:
>
> hi
>
> i have table
> db.define_table('items', Field('name'), Field('created_by'),
> Field('modified_by'))
>
> fields `created_by` and `modified_by` has defined relation to
> db.auth_user.user_id (not auth_user.id)
>
> how to programatically create virtual fields created_by.full_name and
> modified_by.full_name?
>
>
> lefts = []
> auth_user_fields = ('created_by', 'modified_by')
> for field in auth_user_fields:
> table = db.auth_user.with_alias(field)
> table.full_name = self.db.Field.Virtual('full_name', lambda
> row, field=field: '%s %s' % (row[field].first_name, row[field].last_name))
> lefts.append(table.on(table.user_id==self.model[field]))
>
> rows = db(db.items).select(left=lefts)
>
> but `rows` in last line contains only fields/columns from `db.items` ,
> aliased `created_by` and `modified_by` `auth_user` table is missing
>
> am i doing something wrong?
>
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