From acf0e761bf7aacf341ff3a56b3e1359e2070e12f Mon Sep 17 00:00:00 2001
From: bob-white <robert.wd.white@gmail.com>
Date: Sun, 13 Aug 2017 00:53:56 -0500
Subject: [PATCH] Adding a filtered view class

This creates a view into an ObservableCollection and lets you apply a
filter against that view.

Each FilteredView can be bound to a different control, but still
reference the same underlying collection.

When the base collection changes, each view is updated.
---
 mGui/observable.py | 50 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 48 insertions(+), 2 deletions(-)

diff --git a/mGui/observable.py b/mGui/observable.py
index 0db2223..6fdd55c 100644
--- a/mGui/observable.py
+++ b/mGui/observable.py
@@ -3,7 +3,8 @@
 @author: stevetheodore
 """
 import itertools
-from collections import MutableSequence, Sequence
+from weakref import proxy
+from collections import MutableSequence, Sequence, Sized
 
 from mGui.bindings import BindableObject
 from mGui.events import MayaEvent, Event
@@ -117,9 +118,11 @@ def reverse(self):
         self.update_bindings()
         self.onCollectionChanged(sorted=True)
 
+    def __repr__(self):
+        return '{0.__class__.__name__}({0._internal_collection!r})'.format(self)
 
-class ImmediateObservableCollection(ObservableCollection):
 
+class ImmediateObservableCollection(ObservableCollection):
 
     def __init__(self, *items):
         super(ImmediateObservableCollection, self).__init__(*items)
@@ -200,6 +203,49 @@ def __getitem__(self, item):
         return self.view.__getitem__(item)
 
 
+class FilteredView(Sized, BindableObject):
+    """
+    Creates a filtered view of an observable.
+
+    This allows us to create multiple views from a single observable collection, 
+    and each view can be bound to a different control.
+
+    """
+
+    _BIND_SRC = 'view'
+    _BIND_TGT = None
+
+    def __init__(self, observable, _filter=lambda x: x):
+        if not isinstance(observable, ObservableCollection):
+            raise TypeError()
+        self._observable = proxy(observable)
+        self._filter = _filter
+        self._observable.onCollectionChanged += self.update_bindings
+
+    def __len__(self):
+        return len(self.view)
+
+    @property
+    def view(self):
+        if self._observable is None:
+            return tuple()
+        return tuple(itertools.ifilter(self._filter, self._observable))
+
+    @property
+    def viewCount(self):
+        return len(self)
+
+    def __repr__(self):
+        return '{0.__class__.__name__}({0._observable!r}, {0._filter!r})'.format(self)
+
+    def update_filter(self, _filter=lambda x: x):
+        self._filter = _filter
+        self.update_bindings()
+
+    def update_bindings(self, *args, **kwargs):
+        super(FilteredView, self).update_bindings()
+
+
 class BoundCollection(Sequence, BindableObject):
     """
     An iterable object which can be bound to a collection. When the source