iOS XML parsing on main or background thread

When parsing XML in Objective-C on an iOS app, when can the main thread be used and when should the parsing happen on a background thread?开发者_C百科 Can the main thread handle SAX parsing on small documents, or should all XML parsing happen in the background?

I normally do all of my data processing on a background thread. This ensures that the UI thread isn't blocked at any point in time by whatever I'm doing.

Anything that does not call into UIKit (UIView & it's subclasses) or even suggests that it might render to the screen is completely safe to do off the main thread.

I've got several apps that process XML on a background thread. I would suggest using a NSOperation that you pass the entire XML document to, allow it to process it completely or provide a series of delegate methods that notify the main thread about it's progress. If you plan on using core data, might i suggest my own NSOperation abstract class for doing background imports.

In fact you can do some rendering on a background thread, but you must pick your API's very carefully.