* [OTRestModel allObjectsOrderedBy:]

* buildModelFromXML: guards against nils
* added error property to OTRestResponse, will get set on connectionDidFail:withError:
* also added errorDescription which either uses the error description or the first <error> element in the document

OTRestClient.m

@@ -73,7 +73,7 @@ static OTRestClient* sharedClient = nil;
 - (OTRestRequest*)get:(NSString*)resourcePath delegate:(id)delegate callback:(SEL)callback {
 	OTRestRequest* request = [[OTRestRequest alloc] initWithURL:[self URLForResourcePath:resourcePath] delegate:delegate callback:callback];
 	request.additionalHTTPHeaders = _HTTPHeaders;
-	[request get];	
+	[request get];
 	return request;
 }
 

OTRestModel.h

@@ -17,10 +17,6 @@
 	#define context [[[NSApplication sharedApplication] delegate] managedObjectContext]
 #endif
 
-
-
-#define kResponseUserInfoKey @"ResponseUserInfoKey"
-
 #define kRailsToXMLDateFormatterString @"yyyy-MM-dd'T'HH:mm:ss'Z'" // 2009-08-08T17:23:59Z
 
 @interface OTRestModel : NSManagedObject   {
@@ -37,6 +33,7 @@
 
 // finders
 + (NSArray*)allObjects;
++ (NSArray*)allObjectsOrderedBy:(NSString*)key;
 + (id)objectWithRestId:(NSNumber*)restId;
 + (NSArray*)collectionWithRequest:(NSFetchRequest*)request;
 + (NSFetchRequest*)request;

OTRestModel.m

@@ -84,6 +84,19 @@
 	return [self collectionWithRequest:[self request]];
 }
 
++ (NSArray*)allObjectsOrderedBy:(NSString*)key {
+	NSFetchRequest* request = [self request];
+	
+	NSSortDescriptor* sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:key 
+																	ascending:YES
+																	 selector:@selector(caseInsensitiveCompare:)] 
+										autorelease];
+	NSArray* sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
+	[request setSortDescriptors:sortDescriptors];
+	
+	return [self collectionWithRequest:request];
+}
+
 + (id)createOrUpdateAttributesFromXML:(Element*)XML {
 	NSNumber* objectId = [XML contentsNumberOfChildElement:@"id"];
 	id object = [self objectWithRestId:objectId];

OTRestModelMapper.m

@@ -29,6 +29,9 @@
 }
 
 - (id)buildModelFromXML:(Element*)XML {
+	if (XML == nil) {
+		return nil;
+	}
 	NSString* elementName = [XML key];
 	Class class = [_elementToClassMappings objectForKey:elementName];
 	if (class == nil) {

OTRestResponse.h

@@ -14,6 +14,7 @@
 	OTRestRequest* _request;
 	NSHTTPURLResponse* _httpURLResponse;
 	NSMutableData* _payload;
+	NSError* _error;
 }
 
 /**
@@ -46,6 +47,12 @@
  */
 @property(nonatomic, readonly) NSData* payload;
 
+/**
+ * The error returned if the url connection fails
+ */
+@property(nonatomic, readonly) NSError* error;
+
+
 /**
  * Initialize a new response object for a REST request
  */
@@ -66,4 +73,11 @@
  */
 - (DocumentRoot*)payloadXMLDocument;
 
+/**
+ * Will determine if there is an error object and use it's localized message
+ * or
+ * take the first <error> element out of the returned document.
+ */
+- (NSString*)errorDescription;
+
 @end

OTRestResponse.m

@@ -10,11 +10,12 @@
 
 @implementation OTRestResponse
 
-@synthesize payload = _payload, request = _request;
+@synthesize payload = _payload, request = _request, error = _error;
 
 - (id)init {
 	if (self = [super init]) {
 		_payload = [[NSMutableData alloc] init];
+		_error = nil;
 	}
 	
 	return self;
@@ -31,6 +32,7 @@
 	[_httpURLResponse release];
 	[_payload release];
 	[_request release];
+	[_error release];
 	[super dealloc];
 }
 
@@ -47,6 +49,11 @@
 	[[_request delegate] performSelector:[_request callback] withObject:self];	
 }
 
+- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
+	_error = [error retain];
+	[[_request delegate] performSelector:[_request callback] withObject:self];
+}
+
 - (NSString*)localizedStatusCodeString {
 	return [NSHTTPURLResponse localizedStringForStatusCode:[self statusCode]];
 }
@@ -59,6 +66,16 @@
 	return [DocumentRoot parseXML:[self payloadString]];
 }
 
+- (NSString*)errorDescription {
+	NSString* desc;
+	if (_error != nil) {
+		desc = [_error localizedDescription];
+	} else {
+		desc = [[(Element*)[self payloadXMLDocument] selectElement:@"error"] contentsText];
+	}
+	return desc;
+}
+
 - (NSURL*)URL {
 	return [_httpURLResponse URL];
 }