Renamed Polymorphic mapping to dynamic mapping after consulting with the community. Dropped abstract superclass in favor of a RKObjectMappingDefinition protocol. Caught missing cases with dynamic object mapping + targetObject. Updated docs and method signatures to reflect the updates.

Code/ObjectMapping/RKObjectDynamicMapping.m

@@ -0,0 +1,140 @@
+//
+//  RKDynamicObjectMapping.m
+//  RestKit
+//
+//  Created by Blake Watters on 7/28/11.
+//  Copyright 2011 Two Toasters. All rights reserved.
+//
+
+#import "RKObjectDynamicMapping.h"
+#import "../Support/RKLog.h"
+
+// Set Logging Component
+#undef RKLogComponent
+#define RKLogComponent lcl_cRestKitObjectMapping
+
+// Implemented in RKObjectMappingOperation
+BOOL RKObjectIsValueEqualToValue(id sourceValue, id destinationValue);
+
+@interface RKObjectDynamicMappingMatcher : NSObject {
+    NSString* _keyPath;
+    id _value;
+    RKObjectMapping* _objectMapping;
+}
+
+@property (nonatomic, readonly) RKObjectMapping* objectMapping;
+
+- (id)initWithKey:(NSString*)key value:(id)value objectMapping:(RKObjectMapping*)objectMapping;
+- (BOOL)isMatchForData:(id)data;
+- (NSString*)matchDescription;
+@end
+
+@implementation RKObjectDynamicMappingMatcher
+
+@synthesize objectMapping = _objectMapping;
+
+- (id)initWithKey:(NSString*)key value:(id)value objectMapping:(RKObjectMapping*)objectMapping {
+    self = [super init];
+    if (self) {
+        _keyPath = [key retain];
+        _value = [value retain];
+        _objectMapping = [objectMapping retain];
+    }
+    
+    return self;
+}
+
+- (void)dealloc {
+    [_keyPath release];
+    [_value release];
+    [_objectMapping release];
+    [super dealloc];
+}
+
+- (BOOL)isMatchForData:(id)data {
+    return RKObjectIsValueEqualToValue([data valueForKeyPath:_keyPath], _value);
+}
+
+- (NSString*)matchDescription {
+    return [NSString stringWithFormat:@"%@ == %@", _keyPath, _value];
+}
+
+@end
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+@implementation RKObjectDynamicMapping
+
+@synthesize delegate = _delegate;
+@synthesize objectMappingForDataBlock = _objectMappingForDataBlock;
+@synthesize forceCollectionMapping = _forceCollectionMapping;
+
++ (RKObjectDynamicMapping*)dynamicMapping {
+    return [[self new] autorelease];
+}
+
+#if NS_BLOCKS_AVAILABLE
+
++ (RKObjectDynamicMapping*)dynamicMappingWithBlock:(void(^)(RKObjectDynamicMapping*))block {
+    RKObjectDynamicMapping* mapping = [self dynamicMapping];
+    block(mapping);
+    return mapping;
+}
+
+#endif
+
+- (id)init {
+    self = [super init];
+    if (self) {
+        _matchers = [NSMutableArray new];
+    }
+    
+    return self;
+}
+
+- (void)dealloc {
+    [_matchers release];
+    [super dealloc];
+}
+
+- (void)setObjectMapping:(RKObjectMapping*)objectMapping whenValueOfKeyPath:(NSString*)keyPath isEqualTo:(id)value {
+    RKLogDebug(@"Adding dynamic object mapping for key '%@' with value '%@' to destination class: %@", keyPath, value, NSStringFromClass(objectMapping.objectClass));
+    RKObjectDynamicMappingMatcher* matcher = [[RKObjectDynamicMappingMatcher alloc] initWithKey:keyPath value:value objectMapping:objectMapping];
+    [_matchers addObject:matcher];
+    [matcher release];
+}
+
+- (RKObjectMapping*)objectMappingForDictionary:(NSDictionary*)data {
+    NSAssert([data isKindOfClass:[NSDictionary class]], @"Dynamic object mapping can only be performed on NSDictionary mappables, got %@", NSStringFromClass([data class]));
+    RKObjectMapping* mapping = nil;
+    
+    RKLogTrace(@"Performing dynamic object mapping for mappable data: %@", data);
+    
+    // Consult the declarative matchers first
+    for (RKObjectDynamicMappingMatcher* matcher in _matchers) {
+        if ([matcher isMatchForData:data]) {
+            RKLogTrace(@"Found declarative match for data: %@.", [matcher matchDescription]);
+            return matcher.objectMapping;
+        }
+    }
+    
+    // Otherwise consult the delegates
+    if (self.delegate) {
+        mapping = [self.delegate objectMappingForData:data];
+        if (mapping) {
+            RKLogTrace(@"Found dynamic delegate match. Delegate = %@", self.delegate);
+            return mapping;
+        }
+    }
+    
+    if (self.objectMappingForDataBlock) {        
+        mapping = self.objectMappingForDataBlock(data);
+        if (mapping) {
+            RKLogTrace(@"Found dynamic delegateBlock match. objectMappingForDataBlock = %@", self.objectMappingForDataBlock);
+        }
+    }
+    
+    return mapping;
+}
+
+@end