Introduce a new heuristic based approach for determining if a response can skip the mapping process. Also introduces a new Network + CoreData logging component and reduces the chattiness of the debug logging level for Core Data Network events.

Code/Network/RKManagedObjectRequestOperation.m

@@ -35,13 +35,12 @@
 
 // Set Logging Component
 #undef RKLogComponent
-#define RKLogComponent RKlcl_cRestKitCoreData
+#define RKLogComponent RKlcl_cRestKitNetworkCoreData
 
 @interface RKEntityMappingEvent : NSObject
 @property (nonatomic, copy) id rootKey;
 @property (nonatomic, copy) NSString *keyPath;
 @property (nonatomic, strong) RKEntityMapping *entityMapping;
-@property (nonatomic, readonly) BOOL canSkipMapping;
 
 + (instancetype)eventWithRootKey:(id)rootKey keyPath:(NSString *)keyPath entityMapping:(RKEntityMapping *)entityMapping;
 @end
@@ -299,6 +298,8 @@ static NSURL *RKRelativeURLFromURLAndResponseDescriptors(NSURL *URL, NSArray *re
 @property (nonatomic, strong, readwrite) RKMappingResult *mappingResult;
 @property (nonatomic, copy) id (^willMapDeserializedResponseBlock)(id deserializedResponseBody);
 @property (nonatomic, strong) NSArray *entityMappingEvents;
+
+@property (nonatomic, strong) NSCachedURLResponse *cachedResponse;
 @end
 
 @implementation RKManagedObjectRequestOperation
@@ -312,6 +313,7 @@ static NSURL *RKRelativeURLFromURLAndResponseDescriptors(NSURL *URL, NSArray *re
     if (self) {
         self.savesToPersistentStore = YES;
         self.deletesOrphanedObjects = YES;
+        self.cachedResponse = [[NSURLCache sharedURLCache] cachedResponseForRequest:requestOperation.request];
     }
     return self;
 }
@@ -372,14 +374,31 @@ static NSURL *RKRelativeURLFromURLAndResponseDescriptors(NSURL *URL, NSArray *re
 // RKResponseHasBeenMappedCacheUserInfoKey is stored by RKObjectRequestOperation
 - (BOOL)canSkipMapping
 {
-    NSCachedURLResponse *cachedResponse = [[NSURLCache sharedURLCache] cachedResponseForRequest:self.HTTPRequestOperation.request];
+    // Is the request cacheable
+    if (!self.cachedResponse) return NO;
+    NSURLRequest *request = self.HTTPRequestOperation.request;
+    if (! [[request HTTPMethod] isEqualToString:@"GET"] && ! [[request HTTPMethod] isEqualToString:@"HEAD"]) return NO;
+    NSHTTPURLResponse *response = (NSHTTPURLResponse *)self.HTTPRequestOperation.response;
+    if (! [RKCacheableStatusCodes() containsIndex:response.statusCode]) return NO;
+
+    // Check for a change in the Etag
+    NSString *cachedEtag = [[(NSHTTPURLResponse *)[self.cachedResponse response] allHeaderFields] objectForKey:@"Etag"];
+    NSString *responseEtag = [[response allHeaderFields] objectForKey:@"Etag"];
+    if (! [cachedEtag isEqualToString:responseEtag]) return NO;
+
+    // Response data has changed
+    NSData *responseData = self.HTTPRequestOperation.responseData;
+    if (! [responseData isEqualToData:[self.cachedResponse data]]) return NO;
+
+    // Check that we have mapped this response previously
+    NSCachedURLResponse *cachedResponse = [[NSURLCache sharedURLCache] cachedResponseForRequest:request];
     return [[cachedResponse.userInfo objectForKey:RKResponseHasBeenMappedCacheUserInfoKey] boolValue];
 }
 
 - (RKMappingResult *)performMappingOnResponse:(NSError **)error
 {
-    if (self.canSkipMapping) {
-        RKLogDebug(@"Managed object mapping requested for cached response: skipping mapping...");
+    if ([self canSkipMapping]) {
+        RKLogDebug(@"Managed object mapping requested for cached response which was previously mapped: skipping...");
         NSURL *URL = RKRelativeURLFromURLAndResponseDescriptors(self.HTTPRequestOperation.response.URL, self.responseDescriptors);
         NSArray *fetchRequests = RKArrayOfFetchRequestFromBlocksWithURL(self.fetchRequestBlocks, URL);
         NSMutableArray *managedObjects = [NSMutableArray array];
@@ -470,7 +489,7 @@ static NSURL *RKRelativeURLFromURLAndResponseDescriptors(NSURL *URL, NSArray *re
             RKLogTrace(@"Fetched local objects matching URL '%@' with fetch request '%@': %@", URL, fetchRequest, _blockObjects);
             [localObjects addObjectsFromArray:_blockObjects];
         } else {
-            RKLogDebug(@"Fetch request block %@ returned nil fetch request for URL: '%@'", fetchRequestBlock, URL);
+            RKLogTrace(@"Fetch request block %@ returned nil fetch request for URL: '%@'", fetchRequestBlock, URL);
         }
     }
 
@@ -489,7 +508,7 @@ static NSURL *RKRelativeURLFromURLAndResponseDescriptors(NSURL *URL, NSArray *re
         return YES;
     }
     
-    if (self.canSkipMapping) {
+    if ([self canSkipMapping]) {
         RKLogDebug(@"Skipping deletion of orphaned objects: 304 (Not Modified) status code encountered");
         return YES;
     }

Code/ObjectMapping/RKHTTPUtilities.h

@@ -78,6 +78,13 @@ NSRange RKStatusCodeRangeForClass(RKStatusCodeClass statusCodeClass);
  */
 NSIndexSet *RKStatusCodeIndexSetForClass(RKStatusCodeClass statusCodeClass);
 
+/**
+ Creates and returns a new index set including all HTTP response status codes that are cacheable.
+
+ @return A new index set containing all cacheable status codes.
+ */
+NSIndexSet *RKCacheableStatusCodes();
+
 /**
  Returns string representation of a given HTTP status code.
  

Code/ObjectMapping/RKHTTPUtilities.m

@@ -32,6 +32,20 @@ NSIndexSet *RKStatusCodeIndexSetForClass(RKStatusCodeClass statusCodeClass)
     return [NSIndexSet indexSetWithIndexesInRange:RKStatusCodeRangeForClass(statusCodeClass)];
 }
 
+NSIndexSet *RKCacheableStatusCodes()
+{
+    NSMutableIndexSet *cacheableStatusCodes = [NSMutableIndexSet indexSet];
+    [cacheableStatusCodes addIndex:200];
+    [cacheableStatusCodes addIndex:304];
+    [cacheableStatusCodes addIndex:203];
+    [cacheableStatusCodes addIndex:300];
+    [cacheableStatusCodes addIndex:301];
+    [cacheableStatusCodes addIndex:302];
+    [cacheableStatusCodes addIndex:307];
+    [cacheableStatusCodes addIndex:410];
+    return cacheableStatusCodes;
+}
+
 NSString *RKStringFromRequestMethod(RKRequestMethod method)
 {
     switch (method) {

Code/Support/lcl_config_components_RK.h

@@ -54,6 +54,7 @@ _RKlcl_component(RestKit,                     "restkit",
 _RKlcl_component(RestKitCoreData,             "restkit.core_data",                "RestKit/CoreData")
 _RKlcl_component(RestKitCoreDataCache,        "restkit.core_data.cache",          "RestKit/CoreData/Cache")
 _RKlcl_component(RestKitNetwork,              "restkit.network",                  "RestKit/Network")
+_RKlcl_component(RestKitNetworkCoreData,      "restkit.network.core_data",        "RestKit/Network/CoreData")
 _RKlcl_component(RestKitObjectMapping,        "restkit.object_mapping",           "RestKit/ObjectMapping")
 _RKlcl_component(RestKitSearch,               "restkit.search",                   "RestKit/Search")
 _RKlcl_component(RestKitSupport,              "restkit.support",                  "RestKit/Support")