Allow collision keys in the XML parser in order to support RSS feeds.

RSS feeds tend to allow their feed items to be placed in the channel
object as flat items, instead of within an array. The original XML parser
implementation assumed that keys were always unique, but this is not the
case with RSS feeds. Options were added to make it possible to toggle this
functionality.

src/TTURLXMLResponse.m

@@ -26,7 +26,8 @@
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 @implementation TTURLXMLResponse
 
-@synthesize rootObject = _rootObject;
+@synthesize rootObject  = _rootObject;
+@synthesize isRssFeed   = _isRssFeed;
 
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
@@ -52,9 +53,12 @@ - (NSError*)request:(TTURLRequest*)request processResponse:(NSHTTPURLResponse*)r
   TTDASSERT(nil == _rootObject);
 
   if ([data isKindOfClass:[NSData class]]) {
-    NSLog(@"Data: %@", [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease]);
+    //NSLog(@"Data: %@", [[[NSString alloc]
+    //  initWithData: data
+    //      encoding: NSUTF8StringEncoding] autorelease]);
     TTXMLParser* parser = [[TTXMLParser alloc] initWithData:data];
     parser.delegate = self;
+    parser.treatDuplicateKeysAsArrayItems = self.isRssFeed;
     [parser parse];
     _rootObject = [parser.rootObject retain];
     TT_RELEASE_SAFELY(parser);

src/TTXMLParser.m

@@ -36,7 +36,8 @@
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 @implementation TTXMLParser
 
-@synthesize rootObject = _rootObject;
+@synthesize rootObject                      = _rootObject;
+@synthesize treatDuplicateKeysAsArrayItems  = _treatDuplicateKeysAsArrayItems;
 
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
@@ -82,8 +83,8 @@ - (id)allocObjectForElementName: (NSString*) elementName
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 - (void)addChild:(id)childObject toObject:(id)object {
-  // Is this an internal common "array" type?
 
+  // Is this an internal common "array" type?
   if ([object isKindOfClass:[NSDictionary class]] &&
       [[object objectForKey:kPrivateKey_EntityType] isEqualToString:kCommonType_Array]) {
 
@@ -92,10 +93,37 @@ - (void)addChild:(id)childObject toObject:(id)object {
       [[object objectForKey:kPrivateKey_Array] addObject:childObject];
     }
 
+  // Is it an unknown dictionary type?
   } else if ([object isKindOfClass:[NSDictionary class]] &&
       [[object objectForKey:kPrivateKey_EntityType] isEqualToString:kCommonXMLType_Unknown]) {
-    // It's an unknown dictionary type, let's just add this object then.
-    [object setObject:childObject forKey:[childObject objectForKey:kPrivateKey_EntityName]];
+
+    if (self.treatDuplicateKeysAsArrayItems) {
+      NSString* entityName = [childObject objectForKey:kPrivateKey_EntityName];
+      id entityObject = [object objectForKey:entityName];
+      if (nil == entityObject) {
+        // No collision, add it!
+        [object setObject:childObject forKey:entityName];
+
+      } else {
+        // Collision, check if it's already an array.
+        if (TTIsArrayWithItems(entityObject)) {
+          [entityObject addObject:childObject];
+        } else {
+          NSMutableArray* array = [[NSMutableArray alloc] init];
+          [array addObject:entityObject];
+          [array addObject:childObject];
+          [object setObject:array forKey:entityName];
+          TT_RELEASE_SAFELY(array);
+        }
+      }
+
+    } else {
+      // Avoid overwriting existing keys.
+      // If this is asserting, you probably need treatDuplicateKeysAsArrayItems set to YES.
+      TTDASSERT(nil == [object objectForKey:[childObject objectForKey:kPrivateKey_EntityName]]);
+
+      [object setObject:childObject forKey:[childObject objectForKey:kPrivateKey_EntityName]];
+    }
   }
 }
 
@@ -215,6 +243,12 @@ - (void)         parser: (NSXMLParser*) parser
 }
 
 
+///////////////////////////////////////////////////////////////////////////////////////////////////
+- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError {
+  TTDERROR(@"Error parsing the XML: %@", [parseError localizedDescription]);
+}
+
+
 @end
 
 

src/Three20/TTURLXMLResponse.h

@@ -23,9 +23,18 @@
  * parse HTML pages that are likely to have invalid markup.
  */
 @interface TTURLXMLResponse : NSObject <TTURLResponse> {
-  id _rootObject;
+  id    _rootObject;
+  BOOL  _isRssFeed;
 }
 
-@property (nonatomic, retain, readonly) id rootObject;
+@property (nonatomic, retain, readonly) id    rootObject;
+
+/**
+ * Is this XML response an RSS feed? This distinction is necessary in order to allow duplicate
+ * keys in the XML objects.
+ *
+ * @default NO
+ */
+@property (nonatomic, assign)           BOOL  isRssFeed;
 
 @end

src/Three20/TTXMLParser.h

@@ -27,10 +27,22 @@ extern NSString* kCommonXMLType_Unknown;
 @private
   id              _rootObject;
 
+  BOOL            _treatDuplicateKeysAsArrayItems;
+
   NSMutableArray* _objectStack;
 }
 
-@property (nonatomic, readonly) id rootObject;
+@property (nonatomic, readonly) id    rootObject;
+
+/**
+ * When a duplicate key is encountered, the key's value is turned into an array and both
+ * the original item and the new duplicate item are added to the array. Any subsequent duplicates
+ * are also added to this array.
+ * This is useful for RSS feeds, where feed items are presented inline (and not as array items).
+ *
+ * @default NO
+ */
+@property (nonatomic, assign)   BOOL  treatDuplicateKeysAsArrayItems;
 
 @end