Add configurable error parsing to the object mapper.

Code/ObjectMapping/RKObjectLoader.m

@@ -101,20 +101,7 @@
 		[_delegate objectLoader:self didFailWithError:response.failureError];
 		return YES;
 	} else if ([response isError]) {
-		NSString* errorMessage = nil;
-		if ([response isJSON]) {
-			// TODO: Processing errors should be moved to a delegate to accommodate non-Rails services...
-			errorMessage = [[[response bodyAsJSON] valueForKey:@"errors"] componentsJoinedByString:@", "];
-		}
-		if (nil == errorMessage) {
-			errorMessage = [response bodyAsString];
-		}
-		NSDictionary *userInfo = [NSDictionary dictionaryWithObjectsAndKeys:
-								  errorMessage, NSLocalizedDescriptionKey,
-								  nil];		
-		NSError *error = [NSError errorWithDomain:RKRestKitErrorDomain code:RKObjectLoaderRemoteSystemError userInfo:userInfo];
-		
-		[_delegate objectLoader:self didFailWithError:error];
+		[_delegate objectLoader:self didFailWithError:[_mapper parseErrorFromString:[response bodyAsString]]];
 		return YES;
 	}
 	

Code/ObjectMapping/RKObjectMapper.h

@@ -26,6 +26,8 @@ typedef enum {
 	NSArray* _dateFormats;
 	NSTimeZone* _remoteTimeZone;
 	NSTimeZone* _localTimeZone;
+	NSString* _errorsKeyPath;
+	NSString* _errorsConcatenationString;
 }
 
 /**
@@ -56,6 +58,16 @@ typedef enum {
  */
 @property(nonatomic, retain) NSTimeZone* localTimeZone;
 
+/*
+ * This defines the key path to look for errors in a string. defaults to @"errors"
+ */
+@property (nonatomic, copy) NSString* errorsKeyPath;
+
+/*
+ * This string is used to concatenate the errors returned in a string. defaults to @", "
+ */
+@property (nonatomic, copy) NSString* errorsConcatenationString;
+
 /**
  * Register a mapping for a given class for an XML element with the given tag name
  * will blow up if the class does not respond to elementToPropertyMappings and elementToRelationshipMappings
@@ -72,6 +84,12 @@ typedef enum {
  */
 - (id)mapFromString:(NSString*)string;
 
+/**
+ * Digests a string (such as an error response body) in to an NSError.
+ * It should only be called for a string you know contains an error.
+ */
+- (NSError*)parseErrorFromString:(NSString*)string;
+
 /**
  * Sets the properties and relationships serialized in the string into the model instance
  * provided

Code/ObjectMapping/RKObjectMapper.m

@@ -13,6 +13,7 @@
 #import "RKObjectMapper.h"
 #import "NSDictionary+RKAdditions.h"
 #import "RKJSONParser.h"
+#import "Errors.h"
 
 // Default format string for date and time objects from Rails
 // TODO: Rails specifics should probably move elsewhere...
@@ -47,6 +48,8 @@ static const NSString* kRKModelMapperMappingFormatParserKey = @"RKMappingFormatP
 @synthesize dateFormats = _dateFormats;
 @synthesize remoteTimeZone = _remoteTimeZone;
 @synthesize localTimeZone = _localTimeZone;
+@synthesize errorsKeyPath = _errorsKeyPath;
+@synthesize errorsConcatenationString = _errorsConcatenationString;
 
 ///////////////////////////////////////////////////////////////////////////////
 // public
@@ -59,6 +62,8 @@ static const NSString* kRKModelMapperMappingFormatParserKey = @"RKMappingFormatP
 		self.dateFormats = [NSArray arrayWithObjects:kRKModelMapperRailsDateTimeFormatString, kRKModelMapperRailsDateFormatString, nil];
 		self.remoteTimeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
 		self.localTimeZone = [NSTimeZone localTimeZone];
+		self.errorsKeyPath = @"errors";
+		self.errorsConcatenationString = @", ";
 	}
 	return self;
 }
@@ -67,6 +72,8 @@ static const NSString* kRKModelMapperMappingFormatParserKey = @"RKMappingFormatP
 	[_elementToClassMappings release];
 	[_inspector release];
 	[_dateFormats release];
+	[_errorsKeyPath release];
+	[_errorsConcatenationString release];
 	[super dealloc];
 }
 
@@ -101,6 +108,16 @@ static const NSString* kRKModelMapperMappingFormatParserKey = @"RKMappingFormatP
 	return result;
 }
 
+- (NSError*)parseErrorFromString:(NSString*)string {
+	NSString* errorMessage = [[[self parseString:string] valueForKeyPath:_errorsKeyPath] componentsJoinedByString:_errorsConcatenationString];
+	NSDictionary *userInfo = [NSDictionary dictionaryWithObjectsAndKeys:
+							  errorMessage, NSLocalizedDescriptionKey,
+							  nil];
+	NSError *error = [NSError errorWithDomain:RKRestKitErrorDomain code:RKObjectLoaderRemoteSystemError userInfo:userInfo];
+	
+	return error;
+}
+
 - (id)mapFromString:(NSString*)string toClass:(Class)class keyPath:(NSString*)keyPath {
 	id object = [self parseString:string];
 	if (keyPath) {