apt.Cache: Introduce a connect2() callback connector

The new API passes the cache as the first argument to the
callback and allows for other arguments to be passed
as well.

1 files changed, 25 insertions, 0 deletions

diff --git a/apt/cache.py b/apt/cache.py
index 73a95e7c..faad8523 100644
--- a/apt/cache.py
+++ b/apt/cache.py
@@ -78,6 +78,7 @@ class Cache(object):
         self._records = None
         self._list = None
         self._callbacks = {}
+        self._callbacks2 = {}
         self._weakref = weakref.WeakValueDictionary()
         self._changes_count = -1
         self._sorted_set = None
@@ -144,6 +145,10 @@ class Cache(object):
                 else:
                     callback()
 
+        if name in self._callbacks2:
+            for callback, args, kwds in self._callbacks2[name]:
+                    callback(self, *args, **kwds)
+
     def open(self, progress=None):
         """ Open the package cache, after that it can be used like
             a dictionary
@@ -545,6 +550,26 @@ class Cache(object):
             self._callbacks[name] = []
         self._callbacks[name].append(callback)
 
+    def connect2(self, name, callback, *args, **kwds):
+        """Connect to a signal.
+
+        The callback will be passed the cache as an argument, and
+        any arguments passed to this function. Make sure that, if you
+        pass a method of a class as your callback, your class does not
+        contain a reference to the cache.
+
+        Cyclic references to the cache can cause issues if the Cache object
+        is replaced by a new one, because the cache keeps a lot of objects and
+        tens of open file descriptors.
+
+        currently only used for cache_{post,pre}_{changed,open}.
+
+        .. versionadded:: 1.0
+        """
+        if name not in self._callbacks2:
+            self._callbacks2[name] = []
+        self._callbacks2[name].append((callback, args, kwds))
+
     def actiongroup(self):
         """Return an `ActionGroup` object for the current cache.