Adding insertChild:atIndex: method, along with code to test it.

DDXMLElement.h

@@ -38,7 +38,7 @@
 
 #pragma mark --- Children ---
 
-//- (void)insertChild:(DDXMLNode *)child atIndex:(NSUInteger)index;
+- (void)insertChild:(DDXMLNode *)child atIndex:(NSUInteger)index;
 //- (void)insertChildren:(NSArray *)children atIndex:(NSUInteger)index;
 - (void)removeChildAtIndex:(NSUInteger)index;
 - (void)setChildren:(NSArray *)children;

DDXMLElement.m

@@ -524,6 +524,41 @@ - (void)addChild:(DDXMLNode *)child
 	xmlAddChild((xmlNodePtr)genericPtr, (xmlNodePtr)child->genericPtr);
 }
 
+- (void)insertChild:(DDXMLNode *)child atIndex:(NSUInteger)index
+{
+	// NSXML version uses these same assertions
+	DDCheck([child hasParent] == NO, @"Cannot add a child that has a parent; detach or copy first");
+	DDCheck([child isXmlNodePtr], @"Elements can only have text, elements, processing instructions, and comments as children");
+
+	NSUInteger i = 0;
+
+	xmlNodePtr childNodePtr = ((xmlNodePtr)genericPtr)->children;
+	while(childNodePtr != NULL)
+	{
+		// Ignore all but element, comment, text, or processing instruction nodes
+		if([[self class] isXmlNodePtr:(xmlKindPtr)childNodePtr])
+		{
+			if(i == index)
+			{
+				xmlAddPrevSibling(childNodePtr, (xmlNodePtr)child->genericPtr);
+				return;
+			}
+
+			i++;
+		}
+		childNodePtr = childNodePtr->next;
+	}
+
+	if(i == index)
+	{
+		xmlAddChild((xmlNodePtr)genericPtr, (xmlNodePtr)child->genericPtr);
+		return;
+	}
+
+	// NSXML version uses this same assertion
+	DDCheck(NO, @"index (%u) beyond bounds (%u)", (unsigned)index, (unsigned)++i);
+}
+
 - (void)setChildren:(NSArray *)children
 {
 	[self removeAllChildren];

DDXMLTesting.m

@@ -27,6 +27,7 @@ + (void)testElements;
 + (void)testXPath;
 + (void)testNodesForXPath;
 + (void)testNSXMLBugs;
++ (void)testInsertChild;
 @end
 
 @implementation DDXMLTesting
@@ -58,6 +59,7 @@ + (void)performTests
 	[self testXPath];
 	[self testNodesForXPath];
 	[self testNSXMLBugs];
+	[self testInsertChild];
 
 	[self tearDown];
 }
@@ -1432,4 +1434,53 @@ + (void)testNSXMLBugs
 	[pool release];
 }
 
++ (void)testInsertChild
+{
+	NSLog(@"Starting %@...", NSStringFromSelector(_cmd));
+	NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
+
+	NSXMLElement *nsParent = [NSXMLElement elementWithName:@"parent"];
+	DDXMLElement *ddParent = [DDXMLElement elementWithName:@"parent"];
+
+	NSXMLElement *nsChild2 = [NSXMLElement elementWithName:@"child2"];
+	DDXMLElement *ddChild2 = [DDXMLElement elementWithName:@"child2"];
+
+	[nsParent insertChild:nsChild2 atIndex:0];
+	[ddParent insertChild:ddChild2 atIndex:0];
+
+	NSAssert([[nsParent XMLString] isEqualToString:[ddParent XMLString]], @"Failed test 1");
+
+	NSXMLElement *nsChild0 = [NSXMLElement elementWithName:@"child0"];
+	DDXMLElement *ddChild0 = [DDXMLElement elementWithName:@"child0"];
+
+	[nsParent insertChild:nsChild0 atIndex:0];
+	[ddParent insertChild:ddChild0 atIndex:0];
+
+	NSAssert([[nsParent XMLString] isEqualToString:[ddParent XMLString]], @"Failed test 2");
+
+	NSXMLElement *nsChild1 = [NSXMLElement elementWithName:@"child1"];
+	DDXMLElement *ddChild1 = [DDXMLElement elementWithName:@"child1"];
+
+	[nsParent insertChild:nsChild1 atIndex:1];
+	[ddParent insertChild:ddChild1 atIndex:1];
+
+	NSAssert([[nsParent XMLString] isEqualToString:[ddParent XMLString]], @"Failed test 3");
+
+	NSXMLElement *nsChild3 = [NSXMLElement elementWithName:@"child3"];
+	DDXMLElement *ddChild3 = [DDXMLElement elementWithName:@"child3"];
+
+	[nsParent insertChild:nsChild3 atIndex:3];
+	[ddParent insertChild:ddChild3 atIndex:3];
+
+	NSAssert([[nsParent XMLString] isEqualToString:[ddParent XMLString]], @"Failed test 4");
+
+//	NSXMLElement *nsChild5 = [NSXMLElement elementWithName:@"child5"];
+//	DDXMLElement *ddChild5 = [DDXMLElement elementWithName:@"child5"];
+
+//	[nsParent insertChild:nsChild5 atIndex:5];  // Exception - index (5) beyond bounds (5)
+//	[ddParent insertChild:ddChild5 atIndex:5];  // Exception - index (5) beyond bounds (5)
+
+	[pool release];
+}
+
 @end