Fix issues with passing NSErrors into blocks inappropriately.

Code/CoreData/NSManagedObjectContext+RKAdditions.m

@@ -74,14 +74,19 @@
 
 - (BOOL)saveToPersistentStore:(NSError **)error
 {
+    __block NSError *localError = nil;
     NSManagedObjectContext *contextToSave = self;
     while (contextToSave) {
         __block BOOL success;
         [contextToSave performBlockAndWait:^{
-            success = [contextToSave save:error];
+            success = [contextToSave save:&localError];
         }];
 
-        if (! success) return NO;
+        if (! success) {
+            *error = localError;
+            return NO;
+        }
+
         if (! contextToSave.parentContext && contextToSave.persistentStoreCoordinator == nil) {
             RKLogWarning(@"Reached the end of the chain of nested managed object contexts without encountering a persistent store coordinator. Objects are not fully persisted.");
             return NO;

Code/Network/RKManagedObjectRequestOperation.m

@@ -143,6 +143,7 @@
                 RKLogWarning(@"Unable to delete object sent with `DELETE` request: Failed to retrieve object with objectID %@", self.targetObjectID);
                 RKLogCoreDataError(_blockError);
                 _blockSuccess = NO;
+                *error = _blockError;
             }
         }];
     }
@@ -165,6 +166,11 @@
             [self.privateContext performBlockAndWait:^{
                 _blockObjects = [self.privateContext executeFetchRequest:fetchRequest error:&_blockError];
             }];
+
+            if (_blockObjects == nil) {
+                *error = _blockError;
+                return nil;
+            }
             RKLogTrace(@"Fetched local objects matching URL '%@' with fetch request '%@': %@", URL, fetchRequest, _blockObjects);
             [localObjects addObjectsFromArray:_blockObjects];
         } else {
@@ -204,12 +210,20 @@
 
 - (BOOL)saveContext:(NSError **)error
 {
-    BOOL success = YES;
+    __block BOOL success = YES;
+    __block NSError *localError = nil;
     if ([self.privateContext hasChanges]) {
-        success = (self.savesToPersistentStore) ? [self.privateContext saveToPersistentStore:error] : [self.privateContext save:error];
+        if (self.savesToPersistentStore) {
+            success = [self.privateContext saveToPersistentStore:&localError];
+        } else {
+            [self.privateContext performBlockAndWait:^{
+                success = [self.privateContext save:&localError];
+            }];
+        }
         if (! success) {
+            *error = localError;
             RKLogError(@"Failed saving managed object context %@ %@", (self.savesToPersistentStore ? @"to the persistent store" : @""),  self.privateContext);
-            RKLogCoreDataError(*error);
+            RKLogCoreDataError(localError);
         }
     }
 
@@ -219,12 +233,14 @@
 - (BOOL)obtainPermanentObjectIDsForInsertedObjects:(NSError **)error
 {
     __block BOOL _blockSuccess = YES;
+    __block NSError *localError = nil;
     NSArray *insertedObjects = [self.privateContext.insertedObjects allObjects];
     if ([insertedObjects count] > 0) {
         RKLogDebug(@"Obtaining permanent ID's for %ld managed objects", (unsigned long) [insertedObjects count]);
         [self.privateContext performBlockAndWait:^{
-            _blockSuccess = [self.privateContext obtainPermanentIDsForObjects:insertedObjects error:error];
+            _blockSuccess = [self.privateContext obtainPermanentIDsForObjects:insertedObjects error:&localError];
         }];
+        if (!_blockSuccess) *error = localError;
     }
 
     return _blockSuccess;;

Code/Network/RKResponseMapperOperation.m

@@ -100,7 +100,7 @@ NSError *RKErrorFromMappingResult(RKMappingResult *mappingResult)
 - (id)parseResponseData:(NSError **)error
 {
     NSString *MIMEType = [self.response MIMEType];
-    NSError *underlyingError;
+    NSError *underlyingError = nil;
     id object = [RKMIMETypeSerialization objectFromData:self.data MIMEType:MIMEType error:&underlyingError];
     if (! object) {
         NSMutableDictionary *userInfo = [NSMutableDictionary dictionary];