Didn't realize you could make a second query in a Virtual field but makes
sense now that I see it. Although I'd rather not make the extra query (2
actually since longitude would need to do the same thing) so I guess I will
just add latitude and longitude directly to my original select instead of
trying to make them Virtual fields. e.g.
db(db.location.id>0).select(db.location.ALL, db.location.point.st_x(), db.
location.point.st_y())
On Friday, January 3, 2014 4:16:57 AM UTC-5, Paolo Valleri wrote:
> st_*() are db engine functions, you should query the db to get the output
> you are looking for. Given that, in your virtual field you should make a
> new query, something like that:
>
> Field.Virtual('latitude', lambda row: db(db.location.id == row.location.id
> ).select(db.location.point.st_x()).first()[db.location.point.st_x()]
>
> Paolo
>
> On Thursday, January 2, 2014 9:59:14 PM UTC+1, Christian Foster Howes
> wrote:
>>
>> i bet that by the time your lambda is running the point has been
>> converted to a string already. can you see if that is true? i'm not sure
>> how to invoke db functions in a lambda of a virtual field. :(
>>
>> On Wednesday, January 1, 2014 5:50:54 PM UTC-8, User wrote:
>>>
>>> Suppose I have a table like:
>>>
>>> db.define_table('location',
>>> Field(name, 'string'),
>>> Field('point', 'geometry()')
>>> )
>>>
>>> I want to have the latitude and longitude as attributes also (whose
>>> value can be derived from the point field). So I try this:
>>>
>>> db.define_table('location',
>>> Field(name, 'string'),
>>> Field('point', 'geometry()'),
>>> Field.Virtual('latitude', lambda row: row.location.point.st_x()),
>>> Field.Virtual('longitude', lambda row: row.location.point.st_y()),
>>> )
>>>
>>> But it doesn't work and fails silently. The model just doesn't have
>>> latitude or longitude fields. I also tried with Field.Method but this
>>> complains that 'point' is of typer str.
>>>
>>> I guess the complication is that st_x() translates into a database
>>> function. I'm thinking about parsing the point string which is of the form
>>> "POINT(x y)" as a workaround but I'd rather use st_x if someone can show me
>>> how.
>>>
>>
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