Add RKLog helper for displaying detailed key-value validation failure information. closes RestKit#750

Author: blakewatters

Code/ObjectMapping/RKObjectMappingOperation.m

@@ -252,7 +252,8 @@ - (BOOL)validateValue:(id *)value atKeyPath:(NSString*)keyPath {
         success = [self.destinationObject validateValue:value forKeyPath:keyPath error:&_validationError];
         if (!success) {
             if (_validationError) {
-                RKLogError(@"Validation failed while mapping attribute at key path %@ to value %@. Error: %@", keyPath, *value, [_validationError localizedDescription]);
+                RKLogError(@"Validation failed while mapping attribute at key path '%@' to value %@. Error: %@", keyPath, *value, [_validationError localizedDescription]);                
+                RKLogValidationError(_validationError);
             } else {
                 RKLogWarning(@"Destination object %@ rejected attribute value %@ for keyPath %@. Skipping...", self.destinationObject, *value, keyPath);
             }

Code/Support/RKLog.h

@@ -199,3 +199,9 @@ void RKLogInitialize(void);
     Trace    or 6
  */
 void RKLogConfigureFromEnvironment(void);
+
+/**
+ Logs extensive information about an NSError generated as the results
+ of a failed key-value validation error.
+ */
+void RKLogValidationError(NSError *);

Code/Support/RKLog.m

@@ -127,3 +127,35 @@ int RKLogLevelForString(NSString *logLevel, NSString *envVarName)
         return -1;
     }
 }
+
+void RKLogValidationError(NSError *validationError) {
+    if ([[validationError domain] isEqualToString:@"NSCocoaErrorDomain"]) {
+        NSDictionary *userInfo = [validationError userInfo];
+        NSArray *errors = [userInfo valueForKey:@"NSDetailedErrors"];
+        if (errors) {
+            for (NSError *detailedError in errors) {
+                NSDictionary *subUserInfo = [detailedError userInfo];
+                RKLogError(@"Core Data Save Error\n \
+                           NSLocalizedDescription:\t\t%@\n \
+                           NSValidationErrorKey:\t\t\t%@\n \
+                           NSValidationErrorPredicate:\t%@\n \
+                           NSValidationErrorObject:\n%@\n",
+                           [subUserInfo valueForKey:@"NSLocalizedDescription"],
+                           [subUserInfo valueForKey:@"NSValidationErrorKey"],
+                           [subUserInfo valueForKey:@"NSValidationErrorPredicate"],
+                           [subUserInfo valueForKey:@"NSValidationErrorObject"]);
+            }
+        }
+        else {
+            RKLogError(@"Core Data Save Error\n \
+                       NSLocalizedDescription:\t\t%@\n \
+                       NSValidationErrorKey:\t\t\t%@\n \
+                       NSValidationErrorPredicate:\t%@\n \
+                       NSValidationErrorObject:\n%@\n",
+                       [userInfo valueForKey:@"NSLocalizedDescription"],
+                       [userInfo valueForKey:@"NSValidationErrorKey"],
+                       [userInfo valueForKey:@"NSValidationErrorPredicate"],
+                       [userInfo valueForKey:@"NSValidationErrorObject"]);
+        }
+    }
+}