Implements array binding with fine grained change support

Previous implementation supported only one kind of KVO change, this led to incorrect behaviour in case of binding array properties if one of them generated fine grained KVO notifications (insertions, removals, replacements).
flix-tech · Mar 13, 2017 · 2fd8969 · 2fd8969
1 parent 7ff314e
commit 2fd8969
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Showing 2 changed files with 786 additions and 56 deletions.
diff --git a/Sources/MFBBinding.m b/Sources/MFBBinding.m
@@ -300,66 +300,80 @@ - (void)unbind
     }
 }
 
-
-#pragma mark - KVO Methods
-
-- (void)observeValueForKeyPath:(NSString *)keyPath
-                      ofObject:(id)object
-                        change:(NSDictionary<NSString *, id> *)change
-                       context:(void *)context
+- (void)updateObject:(id)object
+          forKeyPath:(NSString *)keyPath
+              change:(NSDictionary<NSString *, id> *)change
+         transformer:(id(^)(NSValueTransformer *, id))transformer
 {
+    if (_flags.updating) {
+        return;
+    }
 
-    if (context == FirstToSecondKey) {
-
-        if (_flags.updating) {
-            return;
-        }
+    id newValue = change[NSKeyValueChangeNewKey];
 
-        id newValue = change[NSKeyValueChangeNewKey];
+    if (newValue == [NSNull null]) {
+        newValue = nil;
+    }
 
-        if (newValue == [NSNull null]) {
-            newValue = nil;
-        }
+    NSValueTransformer *valueTransformer = self.valueTransformer;
 
-        NSValueTransformer *valueTransformer = self.valueTransformer;
+    if (valueTransformer) {
+        newValue = transformer(valueTransformer, newValue);
+    }
 
-        if (valueTransformer) {
-            newValue = [valueTransformer transformedValue:newValue];
+    _flags.updating = YES;
+
+    switch ([change[NSKeyValueChangeKindKey] unsignedIntegerValue]) {
+        case NSKeyValueChangeSetting:
+            [object setValue:newValue forKeyPath:keyPath];
+            break;
+        case NSKeyValueChangeInsertion: {
+            NSMutableArray *proxyArray = [object mutableArrayValueForKeyPath:keyPath];
+            NSIndexSet *indexes = change[NSKeyValueChangeIndexesKey];
+            [proxyArray insertObjects:newValue atIndexes:indexes];
+            break;
+        }
+        case NSKeyValueChangeRemoval: {
+            NSMutableArray *proxyArray = [object mutableArrayValueForKeyPath:keyPath];
+            NSIndexSet *indexes = change[NSKeyValueChangeIndexesKey];
+            [proxyArray removeObjectsAtIndexes:indexes];
+            break;
+        }
+        case NSKeyValueChangeReplacement: {
+            NSMutableArray *proxyArray = [object mutableArrayValueForKeyPath:keyPath];
+            NSIndexSet *indexes = change[NSKeyValueChangeIndexesKey];
+            [proxyArray replaceObjectsAtIndexes:indexes withObjects:newValue];
+            break;
         }
-
-        _flags.updating = YES;
-
-        [_secondObject setValue:newValue forKeyPath:_secondKeyPath];
-
-        _flags.updating = NO;
-
-        return;
     }
 
-    if (context == SecondToFirstKey) {
+    _flags.updating = NO;
+}
 
-        if (_flags.updating) {
-            return;
-        }
+static __auto_type ForwardTransformer = ^(NSValueTransformer *valueTransformer, id value) {
+    return [valueTransformer transformedValue:value];
+};
 
-        id newValue = change[NSKeyValueChangeNewKey];
+static __auto_type ReverseTransformer = ^(NSValueTransformer *valueTransformer, id value) {
+    return [valueTransformer reverseTransformedValue:value];
+};
 
-        if (newValue == [NSNull null]) {
-            newValue = nil;
-        }
 
-        NSValueTransformer *valueTransformer = self.valueTransformer;
+#pragma mark - KVO Methods
 
-        if (valueTransformer) {
-            newValue = [valueTransformer reverseTransformedValue:newValue];
-        }
+- (void)observeValueForKeyPath:(NSString *)keyPath
+                      ofObject:(id)object
+                        change:(NSDictionary<NSString *, id> *)change
+                       context:(void *)context
+{
 
-        _flags.updating = YES;
+    if (context == FirstToSecondKey) {
+        [self updateObject:_secondObject forKeyPath:_secondKeyPath change:change transformer:ForwardTransformer];
+        return;
+    }
 
-        [_firstObject setValue:newValue forKeyPath:_firstKeyPath];
-
-        _flags.updating = NO;
-
+    if (context == SecondToFirstKey) {
+        [self updateObject:_firstObject forKeyPath:_firstKeyPath change:change transformer:ReverseTransformer];
         return;
     }