NEW: bind:toObject: ... now checks if another binding mutually exclusive is already binded. Throws an exception if this is the case.

Controls can implement -isExlusiveBinding: to determine if bindings are exclusive. Defaults to NO.
Exclusive bindings are mainly CPSelectedIndexBinding | CPSelectedTagBinding | CPSelectedValueBinding

AppKit/CPKeyValueBinding.j

@@ -173,6 +173,24 @@ var CPBindingOperationAnd = 0,
     return self;
 }
 
++ (BOOL)isBindingAllowed:(CPString)aBinding forObject:(id)anObject
+{
+    if ([[anObject class] isBindingExclusive:aBinding])
+    {
+        var bindingsForObject = [bindingsMap objectForKey:[anObject UID]],
+            allBindings = [bindingsForObject allKeys],
+            count = [allBindings count];
+
+        while(count--)
+        {
+            if ([[anObject class] isBindingExclusive:allBindings[count]])
+                return NO;
+        }
+    }
+
+    return YES;
+}
+
 - (void)raiseIfNotApplicable:(id)aValue forKeyPath:(CPString)keyPath options:(CPDictionary)options
 {
     if (aValue === CPNotApplicableMarker && [options objectForKey:CPRaisesForNotApplicableKeysBindingOption])
@@ -401,6 +419,11 @@ var CPBindingOperationAnd = 0,
     return [CPBinder class];
 }
 
++ (BOOL)isBindingExclusive:(CPString)aBinding
+{
+    return NO;
+}
+
 - (CPArray)exposedBindings
 {
     var exposedBindings = [],
@@ -429,6 +452,12 @@ var CPBindingOperationAnd = 0,
     if (!anObject || !aKeyPath)
         return CPLog.error("Invalid object or path on " + self + " for " + aBinding);
 
+    if (![CPBinder isBindingAllowed:aBinding forObject:self])
+    {
+        [CPException raise:CPGenericException
+                   reason:@"Cannot bind " + aBinding + " because a binding with the same functionality is already in use."];
+        return;
+    }
     //if (![[self exposedBindings] containsObject:aBinding])
     //    CPLog.warn("No binding exposed on " + self + " for " + aBinding);
 

AppKit/CPPopUpButton.j

@@ -771,13 +771,6 @@ CPPopUpButtonStatePullsDown = CPThemeState("pulls-down");
             [[self selectedItem] setState:CPOffState];
 }
 
-- (void)_reverseSetBinding
-{
-    [_CPPopUpButtonSelectionBinder _reverseSetValueFromExclusiveBinderForObject:self];
-
-    [super _reverseSetBinding];
-}
-
 @end
 
 @implementation CPPopUpButton (BindingSupport)
@@ -800,6 +793,20 @@ CPPopUpButtonStatePullsDown = CPThemeState("pulls-down");
     return [super _binderClassForBinding:aBinding];
 }
 
++ (BOOL)isBindingExclusive:(CPString)aBinding
+{
+    return (aBinding == CPSelectedIndexBinding ||
+           aBinding == CPSelectedTagBinding ||
+           aBinding == CPSelectedValueBinding);
+}
+
+- (void)_reverseSetBinding
+{
+    [_CPPopUpButtonSelectionBinder _reverseSetValueFromExclusiveBinderForObject:self];
+
+    [super _reverseSetBinding];
+}
+
 @end
 
 @implementation _CPPopUpButtonContentBinder : CPBinder

AppKit/CPRadio.j

@@ -407,6 +407,13 @@ var CPRadioGroupRadiosKey           = @"CPRadioGroupRadiosKey",
     return [super _binderClassForBinding:aBinding];
 }
 
++ (BOOL)isBindingExclusive:(CPString)aBinding
+{
+    return (aBinding == CPSelectedIndexBinding ||
+           aBinding == CPSelectedTagBinding ||
+           aBinding == CPSelectedValueBinding);
+}
+
 @end
 
 @implementation _CPRadioGroupSelectionBinder : CPBinder

AppKit/CPSegmentedControl.j

@@ -49,7 +49,6 @@ CPSegmentSwitchTrackingMomentary = 2;
 
     unsigned                _trackingSegment;
     BOOL                    _trackingHighlighted;
-    BOOL                    _hasBinding;
 }
 
 + (CPString)defaultThemeClass
@@ -75,19 +74,6 @@ CPSegmentSwitchTrackingMomentary = 2;
         };
 }
 
-+ (Class)_binderClassForBinding:(CPString)aBinding
-{
-    if ([self _isSelectionBinding:aBinding])
-        return [_CPSegmentedControlBinder class];
-
-    return [super _binderClassForBinding:aBinding];
-}
-
-+ (BOOL)_isSelectionBinding:(CPString)aBinding
-{
-    return (aBinding === CPSelectedIndexBinding || aBinding === CPSelectedLabelBinding || aBinding === CPSelectedTagBinding);
-}
-
 - (id)initWithFrame:(CGRect)aRect
 {
     _segments = [];
@@ -105,27 +91,6 @@ CPSegmentSwitchTrackingMomentary = 2;
     return self;
 }
 
-- (void)bind:(CPString)aBinding toObject:(id)anObject withKeyPath:(CPString)aKeyPath options:(CPDictionary)options
-{
-    if ([[self class] _isSelectionBinding:aBinding] && _trackingMode !== CPSegmentSwitchTrackingSelectOne)
-    {
-        CPLog.warn("Binding " + aBinding + " needs CPSegmentSwitchTrackingSelectOne tracking mode");
-        return;
-    }
-
-    if (_hasBinding)
-        [_CPSegmentedControlBinder unbindAllForObject:self];
-
-    [super bind:aBinding toObject:anObject withKeyPath:aKeyPath options:options];
-
-    _hasBinding = YES;
-}
-
-- (void)_reverseSetBinding
-{
-    [_CPSegmentedControlBinder _reverseSetValueFromExclusiveBinderForObject:self];
-}
-
 /*!
     Returns the tag of the selected segment.
 */
@@ -957,6 +922,44 @@ var CPSegmentedControlSegmentsKey       = "CPSegmentedControlSegmentsKey",
 
 @end
 
+@implementation CPSegmentedControl (BindingSupport)
+
++ (Class)_binderClassForBinding:(CPString)aBinding
+{
+    if ([self _isSelectionBinding:aBinding])
+        return [_CPSegmentedControlBinder class];
+
+    return [super _binderClassForBinding:aBinding];
+}
+
++ (BOOL)_isSelectionBinding:(CPString)aBinding
+{
+    return (aBinding === CPSelectedIndexBinding || aBinding === CPSelectedLabelBinding || aBinding === CPSelectedTagBinding);
+}
+
++ (BOOL)isBindingExclusive:(CPString)aBinding
+{
+    return [self _isSelectionBinding:aBinding];
+}
+
+- (void)bind:(CPString)aBinding toObject:(id)anObject withKeyPath:(CPString)aKeyPath options:(CPDictionary)options
+{
+    if ([[self class] _isSelectionBinding:aBinding] && _trackingMode !== CPSegmentSwitchTrackingSelectOne)
+    {
+        CPLog.warn("Binding " + aBinding + " needs CPSegmentSwitchTrackingSelectOne tracking mode");
+        return;
+    }
+
+    [super bind:aBinding toObject:anObject withKeyPath:aKeyPath options:options];
+}
+
+- (void)_reverseSetBinding
+{
+    [_CPSegmentedControlBinder _reverseSetValueFromExclusiveBinderForObject:self];
+}
+
+@end
+
 var CPSegmentedControlNoSelectionPlaceholder = "CPSegmentedControlNoSelectionPlaceholder";
 
 @implementation _CPSegmentedControlBinder : CPBinder

Tests/AppKit/CPKeyValueBindingTest.j

@@ -342,6 +342,21 @@
     [self assert:@"brie" equals:[control2 objectValue] message:@"control2 objectValue is wrong"];
 }
 
+- (void)testExclusiveBindingsThrowsException
+{
+    var segmented = [[CPSegmentedControl alloc] initWithFrame:CGRectMakeZero()];
+    [segmented setSegmentCount:3];
+
+    var model = [BindingTester testerWithCheese:2];
+
+    [segmented bind:CPSelectedIndexBinding toObject:model withKeyPath:@"cheese" options:nil];
+
+    [self assertThrows:function()
+    {
+        [segmented bind:CPSelectedTagBinding toObject:model withKeyPath:@"cheese" options:nil];
+    }];
+}
+
 @end
 
 @implementation TextField : CPTextField