/usr/share/pyshared/elixir/ext/list.py is in python-elixir 0.7.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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This extension is DEPRECATED. Please use the orderinglist SQLAlchemy
extension instead.
For details:
http://www.sqlalchemy.org/docs/05/reference/ext/orderinglist.html
For an Elixir example:
http://elixir.ematia.de/trac/wiki/Recipes/UsingEntityForOrderedList
or
http://elixir.ematia.de/trac/browser/elixir/0.7.0/tests/test_o2m.py#L155
An ordered-list plugin for Elixir to help you make an entity be able to be
managed in a list-like way. Much inspiration comes from the Ruby on Rails
acts_as_list plugin, which is currently more full-featured than this plugin.
Once you flag an entity with an `acts_as_list()` statement, a column will be
added to the entity called `position` which will be an integer column that is
managed for you by the plugin. You can pass an alternative column name to
the plugin using the `column_name` keyword argument.
In addition, your entity will get a series of new methods attached to it,
including:
+----------------------+------------------------------------------------------+
| Method Name | Description |
+======================+======================================================+
| ``move_lower`` | Move the item lower in the list |
+----------------------+------------------------------------------------------+
| ``move_higher`` | Move the item higher in the list |
+----------------------+------------------------------------------------------+
| ``move_to_bottom`` | Move the item to the bottom of the list |
+----------------------+------------------------------------------------------+
| ``move_to_top`` | Move the item to the top of the list |
+----------------------+------------------------------------------------------+
| ``move_to`` | Move the item to a specific position in the list |
+----------------------+------------------------------------------------------+
Sometimes, your entities that represent list items will be a part of different
lists. To implement this behavior, simply pass the `acts_as_list` statement a
callable that returns a "qualifier" SQLAlchemy expression. This expression will
be added to the generated WHERE clauses used by the plugin.
Example model usage:
.. sourcecode:: python
from elixir import *
from elixir.ext.list import acts_as_list
class ToDo(Entity):
subject = Field(String(128))
owner = ManyToOne('Person')
def qualify(self):
return ToDo.owner_id == self.owner_id
acts_as_list(qualifier=qualify)
class Person(Entity):
name = Field(String(64))
todos = OneToMany('ToDo', order_by='position')
The above example can then be used to manage ordered todo lists for people.
Note that you must set the `order_by` property on the `Person.todo` relation in
order for the relation to respect the ordering. Here is an example of using
this model in practice:
.. sourcecode:: python
p = Person.query.filter_by(name='Jonathan').one()
p.todos.append(ToDo(subject='Three'))
p.todos.append(ToDo(subject='Two'))
p.todos.append(ToDo(subject='One'))
session.commit(); session.clear()
p = Person.query.filter_by(name='Jonathan').one()
p.todos[0].move_to_bottom()
p.todos[2].move_to_top()
session.commit(); session.clear()
p = Person.query.filter_by(name='Jonathan').one()
assert p.todos[0].subject == 'One'
assert p.todos[1].subject == 'Two'
assert p.todos[2].subject == 'Three'
For more examples, refer to the unit tests for this plugin.
'''
from elixir.statements import Statement
from elixir.events import before_insert, before_delete
from sqlalchemy import Column, Integer, select, func, literal, and_
import warnings
__all__ = ['acts_as_list']
__doc_all__ = []
def get_entity_where(instance):
clauses = []
for column in instance.table.primary_key.columns:
instance_value = getattr(instance, column.name)
clauses.append(column == instance_value)
return and_(*clauses)
class ListEntityBuilder(object):
def __init__(self, entity, qualifier=None, column_name='position'):
warnings.warn("The act_as_list extension is deprecated. Please use "
"SQLAlchemy's orderinglist extension instead",
DeprecationWarning, stacklevel=6)
self.entity = entity
self.qualifier_method = qualifier
self.column_name = column_name
def create_non_pk_cols(self):
if self.entity._descriptor.autoload:
for c in self.entity.table.c:
if c.name == self.column_name:
self.position_column = c
if not hasattr(self, 'position_column'):
raise Exception(
"Could not find column '%s' in autoloaded table '%s', "
"needed by entity '%s'." % (self.column_name,
self.entity.table.name, self.entity.__name__))
else:
self.position_column = Column(self.column_name, Integer)
self.entity._descriptor.add_column(self.position_column)
def after_table(self):
position_column = self.position_column
position_column_name = self.column_name
qualifier_method = self.qualifier_method
if not qualifier_method:
qualifier_method = lambda self: None
def _init_position(self):
s = select(
[(func.max(position_column)+1).label('value')],
qualifier_method(self)
).union(
select([literal(1).label('value')])
)
a = s.alias()
# we use a second func.max to get the maximum between 1 and the
# real max position if any exist
setattr(self, position_column_name, select([func.max(a.c.value)]))
# Note that this method could be rewritten more simply like below,
# but because this extension is going to be deprecated anyway,
# I don't want to risk breaking something I don't want to maintain.
# setattr(self, position_column_name, select(
# [func.coalesce(func.max(position_column), 0) + 1],
# qualifier_method(self)
# ))
_init_position = before_insert(_init_position)
def _shift_items(self):
self.table.update(
and_(
position_column > getattr(self, position_column_name),
qualifier_method(self)
),
values={
position_column : position_column - 1
}
).execute()
_shift_items = before_delete(_shift_items)
def move_to_bottom(self):
# move the items that were above this item up one
self.table.update(
and_(
position_column >= getattr(self, position_column_name),
qualifier_method(self)
),
values = {
position_column : position_column - 1
}
).execute()
# move this item to the max position
# MySQL does not support the correlated subquery, so we need to
# execute the query (through scalar()). See ticket #34.
self.table.update(
get_entity_where(self),
values={
position_column : select(
[func.max(position_column) + 1],
qualifier_method(self)
).scalar()
}
).execute()
def move_to_top(self):
self.move_to(1)
def move_to(self, position):
current_position = getattr(self, position_column_name)
# determine which direction we're moving
if position < current_position:
where = and_(
position <= position_column,
position_column < current_position,
qualifier_method(self)
)
modifier = 1
elif position > current_position:
where = and_(
current_position < position_column,
position_column <= position,
qualifier_method(self)
)
modifier = -1
# shift the items in between the current and new positions
self.table.update(where, values = {
position_column : position_column + modifier
}).execute()
# update this item's position to the desired position
self.table.update(get_entity_where(self)) \
.execute(**{position_column_name: position})
def move_lower(self):
# replace for ex.: p.todos.insert(x + 1, p.todos.pop(x))
self.move_to(getattr(self, position_column_name) + 1)
def move_higher(self):
self.move_to(getattr(self, position_column_name) - 1)
# attach new methods to entity
self.entity._init_position = _init_position
self.entity._shift_items = _shift_items
self.entity.move_lower = move_lower
self.entity.move_higher = move_higher
self.entity.move_to_bottom = move_to_bottom
self.entity.move_to_top = move_to_top
self.entity.move_to = move_to
acts_as_list = Statement(ListEntityBuilder)
|