There's mistakes in how this is structured. UserDefinedType represents a type
object applied to a Column. The actual data handled by such a type is not
meant to be an instance of the type itself. ACLItem() here would be its own
class, and UserDefinedType would be the superclass of a class like
"ACLItemType". ACLItemType() is placed on the Column, and its
bind_processor() and result_processor() deal with ACLItem objects.
Once you have the roles of "type" and "value" set up, you'd want to mixin
sqlalchemy.types.MutableType, which alerts the ORM that the value of this type
can change "inline". Note that MutableType is not recommended for high volume
applications as it performs terribly, due to the need for flush() to scan all
"mutables" in the session for changes every time it's called - 0.7 has a new
extension that allows mutable values to send change events in an efficient
manner.
On Jan 13, 2011, at 1:33 PM, A.M. wrote:
> Hello,
>
> I have created an SQLAlchemy type which represents a postgresql aclitem
> (which represents postgresql access control lists). I am able to load and
> save newly-created ACLItems from the database, however, modifying the values
> of an instance of the type does not dirty it for flushing. Is there some
> decorator for dirtying accessors to the type instance convenience methods?
>
> Specifically, modifying any of "grantee", "grantor", "permissions", and
> "grant_option", does not trigger a proper update.
>
> Cheers,
> M
>
> import sqlalchemy.types as types
> import re
> import sqlalchemy.exc
>
> #include/utils/acl.h
> #define ACL_ALL_RIGHTS_STR "arwdDxtXUCTc"
>
> class ACLItem(types.UserDefinedType):
>
> def
> __init__(self,grantee=None,permissions=None,grantor=None,grant_option=False):
> #note that sqlalchemy calls this with None arguments for processing
> self.grantee = grantee
> self.permissions = []
> if permissions:
> for p in permissions:
> self.permissions.append(p)
> self.grantor = grantor
> self.grant_option = grant_option
>
> def get_col_spec(self):
> return 'aclitem'
>
> def bind_processor(self,dialect):
> def acl2string(aclitem):
> return aclitem._as_pgsql_string()
> return acl2string
>
> def compare_values(self,a,b):
> return a._as_pgsql_string() == b._as_pgsql_string()
>
> def _as_pgsql_string(self):
> #convert to string 'user <grantee>=<perms>/<grantor>'
> string_perms = ''
> for perm in self.permissions:
> string_perms += perm
>
> if self.grant_option:
> grant_option = '*'
> else:
> grant_option = ''
> return "user %s=%s%s/%s" %
> (self.grantee,string_perms,grant_option,self.grantor)
>
> @classmethod
> def _from_pgsql_string(klass,aclstring):
> "grantee=perms*/grantor"
> matches = re.match('([^=]+)=([^/\*]+)(\*?)/(\w+)',aclstring)
> if matches is None:
> raise sqlalchemy.exc.DataError(aclstring,[],'')
> grantee = matches.group(1)
> permissions = matches.group(2)
> grant_option = len(matches.group(3))
> grantor = matches.group(4)
> return ACLItem(grantee,permissions,grantor,grant_option)
>
> def result_processor(self,dialect,column_type):
> def string2acl(aclstring):
> return ACLItem._from_pgsql_string(aclstring)
> return string2acl
>
> def has_permission(self,permission_test):
> return permission_test in self.permissions
>
> def set_permission(self,permission,on=True):
> if not self.has_permission(permission):
> if on:
> self.permissions.append(permission)
> else:
> self.permissions.remove(permission)
>
> def clear_permissions(self):
> del self.permissions[:]
>
> def __str__(self):
> return self._as_pgsql_string()
>
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