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Code Issues 32 Releases Wiki Activity

Redo the changes in [7773] in a better way.

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This removes some of the leaky abstraction problems (lifting WhereNode
internals into the Query class) from that commit and makes it possible for
extensions to WhereNode to have access to the field instances. It's also
backwards-compatible with pre-[7773] code, which is also better.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7835 bcc190cf-cafb-0310-a4f2-bffc1f526a37
This commit is contained in:
Malcolm Tredinnick
2008-07-04 06:42:58 +00:00
parent 3b6487130a
commit 6dd2b5468f
4 changed files with 84 additions and 51 deletions
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31
django/utils/tree.py
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@@ -29,6 +29,22 @@ class Node(object):
self.subtree_parents = []
self.negated = negated
# We need this because of django.db.models.query_utils.Q. Q. __init__() is
# problematic, but it is a natural Node subclass in all other respects.
def _new_instance(cls, children=None, connector=None, negated=False):
"""
This is called to create a new instance of this class when we need new
Nodes (or subclasses) in the internal code in this class. Normally, it
just shadows __init__(). However, subclasses with an __init__ signature
that is not an extension of Node.__init__ might need to implement this
method to allow a Node to create a new instance of them (if they have
any extra setting up to do).
"""
obj = Node(children, connector, negated)
obj.__class__ = cls
return obj
_new_instance = classmethod(_new_instance)
def __str__(self):
if self.negated:
return '(NOT (%s: %s))' % (self.connector, ', '.join([str(c) for c
@@ -82,7 +98,8 @@ class Node(object):
else:
self.children.append(node)
else:
obj = Node(self.children, self.connector, self.negated)
obj = self._new_instance(self.children, self.connector,
self.negated)
self.connector = conn_type
self.children = [obj, node]
@@ -96,7 +113,8 @@ class Node(object):
Interpreting the meaning of this negate is up to client code. This
method is useful for implementing "not" arrangements.
"""
self.children = [Node(self.children, self.connector, not self.negated)]
self.children = [self._new_instance(self.children, self.connector,
not self.negated)]
self.connector = self.default
def start_subtree(self, conn_type):
@@ -108,12 +126,13 @@ class Node(object):
if len(self.children) == 1:
self.connector = conn_type
elif self.connector != conn_type:
self.children = [Node(self.children, self.connector, self.negated)]
self.children = [self._new_instance(self.children, self.connector,
self.negated)]
self.connector = conn_type
self.negated = False
self.subtree_parents.append(Node(self.children, self.connector,
self.negated))
self.subtree_parents.append(self.__class__(self.children,
self.connector, self.negated))
self.connector = self.default
self.negated = False
self.children = []
@@ -126,7 +145,7 @@ class Node(object):
the current instances state to be the parent.
"""
obj = self.subtree_parents.pop()
node = Node(self.children, self.connector)
node = self.__class__(self.children, self.connector)
self.connector = obj.connector
self.negated = obj.negated
self.children = obj.children