Jay Freeman (aka Saurik) has updated MobileSubstrate to version 0.9.3367-1 and comes with iOS 4.2.1 compatibility. Those who don’t know, MobileSubstrate is a support framework used by iPhone projects such as WinterBoard, Dock2, and Five Icon Dock.
The general idea is that there are a number of reasons one might want to hook functionality into an existing application. In order to do this there are a few dangerous or complex steps. By centralizing the code for these we can hope to get them right.
As an example, MobileSubstrate provides a simple platform (one integrated with Cydia) for deploying code that gets inserted into graphical applications. Eventually it will be able to provide error handling and fallback support (think of a “Safe Mode”).
As a library, it has started taking on generalized versions of the code in WinterBoard to be able to rapidly generate application hooks. Is not yet documented, but will be when I get the time (hopefully soon?).
Note: If you updated MobileSubstrate and experience a boot loop issue, the problem is due to an extension (Music Control) and not MobileSubstrate. Music Controls has been updated to version 1.3.1-3 and shouldn’t conflict with MobileSubstrate. Let us know in the comments how your update went.
MobileSubstrate is available in Cydia for free.