app/django/contrib/gis/db/backend/util.py
author Madhusudan C.S. <madhusudancs@gmail.com>
Mon, 08 Jun 2009 08:42:13 +0200
changeset 2406 6f966e1a80bc
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Changed the property that holds the minimum age required for Students to participate in a GHOP based program. Added a new property student_min_age_as_of to hold the DateTime from when the minimum age should be reached. Changed student_min_age property to now store the student minimum age as an integer. This all feel more user friendly then letting the program admin calculate the required DateTime. Storing the two properties is then still needed in this case since information might be lost otherwise when the program admin brings up the edit view. Reviewed by: Lennard de Rijk

from types import UnicodeType

def gqn(val):
    """
    The geographic quote name function; used for quoting tables and 
    geometries (they use single rather than the double quotes of the
    backend quotename function).
    """
    if isinstance(val, basestring):
        if isinstance(val, UnicodeType): val = val.encode('ascii')
        return "'%s'" % val
    else:
        return str(val)

class SpatialOperation(object):
    """
    Base class for generating spatial SQL.
    """
    def __init__(self, function='', operator='', result='', beg_subst='', end_subst=''):
        self.function = function
        self.operator = operator
        self.result = result
        self.beg_subst = beg_subst
        try:
            # Try and put the operator and result into to the
            # end substitution.
            self.end_subst = end_subst % (operator, result)
        except TypeError:
            self.end_subst = end_subst

    @property
    def sql_subst(self):
        return ''.join([self.beg_subst, self.end_subst])

    def as_sql(self, geo_col):
        return self.sql_subst % self.params(geo_col)

    def params(self, geo_col):
        return (geo_col, self.operator)

class SpatialFunction(SpatialOperation):
    """
    Base class for generating spatial SQL related to a function.
    """
    def __init__(self, func, beg_subst='%s(%s, %%s', end_subst=')', result='', operator=''):
        # Getting the function prefix.
        kwargs = {'function' : func, 'operator' : operator, 'result' : result,
                  'beg_subst' : beg_subst, 'end_subst' : end_subst,}
        super(SpatialFunction, self).__init__(**kwargs)

    def params(self, geo_col):
        return (self.function, geo_col)