CouchQuery stores error of the last request

Couch/CouchQuery.h

@@ -38,6 +38,7 @@ typedef enum {
     BOOL _descending, _prefetch, _sequences;
     NSArray *_keys;
     NSUInteger _groupLevel;
+    NSError* _error;
 }
 
 /** The design document that contains this view. */
@@ -84,6 +85,9 @@ typedef enum {
 
 @property BOOL sequences;
 
+/** If non-nil, the error of the last execution of the query.
+    If nil, the last exexution of the query was successful */
+@property (readonly,retain) NSError* error;
 
 /** Starts an asynchronous query of the CouchDB view.
     When complete, the operation's resultObject will be the CouchQueryEnumerator. */

Couch/CouchQuery.m

@@ -32,6 +32,10 @@ - (id) initWithDatabase: (CouchDatabase*)db result: (id)result;
 @end
 
 
+@interface CouchQuery ()
+@property (readwrite,retain) NSError *error;
+@end
+
 
 @implementation CouchQuery
 
@@ -63,13 +67,14 @@ - (void) dealloc
     [_startKeyDocID release];
     [_endKeyDocID release];
     [_keys release];
+    [_error release];
     [super dealloc];
 }
 
 
 @synthesize limit=_limit, skip=_skip, descending=_descending, startKey=_startKey, endKey=_endKey,
             prefetch=_prefetch, keys=_keys, groupLevel=_groupLevel, startKeyDocID=_startKeyDocID,
-            endKeyDocID=_endKeyDocID, stale=_stale, sequences=_sequences;
+            endKeyDocID=_endKeyDocID, stale=_stale, sequences=_sequences, error=_error;
 
 
 - (CouchDesignDocument*) designDocument {
@@ -142,10 +147,11 @@ - (CouchQueryEnumerator*) rowsIfChanged {
 
 
 - (NSError*) operation: (RESTOperation*)op willCompleteWithError: (NSError*)error {
-    error = [super operation: op willCompleteWithError: error];
-    if (error)
-        Warn(@"%@ failed with %@", self, error);
-    if (!error && op.httpStatus == 200) {
+    self.error = [super operation: op willCompleteWithError: error];
+    if (_error)
+        Warn(@"%@ failed with %@", self, _error);
+
+    if (!_error && op.httpStatus == 200) {
         NSDictionary* result = $castIf(NSDictionary, op.responseBody.fromJSON);
         NSArray* rows = $castIf(NSArray, [result objectForKey: @"rows"]);
         if (rows) {
@@ -154,10 +160,12 @@ - (NSError*) operation: (RESTOperation*)op willCompleteWithError: (NSError*)erro
                                                                        result: result] autorelease];
         } else {
             Warn(@"Couldn't parse rows from CouchDB view response");
-            error = [RESTOperation errorWithHTTPStatus: 502 message: nil URL: self.URL];
+            self.error = [RESTOperation errorWithHTTPStatus: 502 
+                                               message: @"Couldn't parse rows from CouchDB view response" 
+                                                   URL: self.URL];
         }
     }
-    return error;
+    return _error;
 }